BIOMOLECULE-POLYMER-PHARMACEUTICAL AGENT CONJUGATES FOR DELIVERING THE PHARMACEUTICAL AGENT RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No.63/291937, filed December 20, 2021, which is incorporated herein by reference in its entirety. GOVERNMENT SUPPORT This invention was made with government support under CA220468 awarded by the National Institutes of Health. The government has certain rights in the invention. BACKGROUND Known antibody-drug conjugates (ADCs) may have low drug-to-antibody ratios (DARs), may only be applicable to very high potency drugs and may need a certain hydrophilicity to achieve aqueous conjugation to the antibody. Moreover, ADCs may need specific design and synthesis for each drug to which they are applied. Further, drugs may be exposed to the biological environment, resulting in premature release. There is a need for improved ADCs. SUMMARY OF THE DISCLOSURE In one aspect, the present disclosure provides enyne of Formula (I): or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof. In certain embodiments, an enyne is a compound comprising at least one non-aromatic C=C bond and at least one non-aromatic C≡C bond. In another aspect, the present disclosure provides a enyne of Formula (II): (II) or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof. In another aspect, the present disclosure provides an end-functionalized polymer of Formula (III): (III), or a tautomer, isotopically labeled polymer, or salt thereof. In another aspect, the present disclosure provides a method of preparing an end- functionalized polymer of Formula (III), or a tautomer, isotopically labeled polymer, or salt thereof. In another aspect, the present disclosure provides a conjugate of Formula (IV’): (IV’), or a tautomer, isotopically labeled conjugate, or salt thereof. In another aspect, the present disclosure provides a conjugate of Formula (IV): (IV), or a tautomer, isotopically labeled conjugate, or salt thereof. In another aspect, the present disclosure provides a method of preparing a conjugate of Formula (IV’), or a tautomer, isotopically labeled conjugate, or salt thereof. In another aspect, the present disclosure provides a method of preparing a conjugate of Formula (IV), or a tautomer, isotopically labeled conjugate, or salt thereof. In other aspects, the present disclosure provides compositions and kits that comprise the enyne, end-functionalized polymer, or conjugate. In other aspects, the present disclosure provides certain methods of using the enynes, end-functionalized polymers, conjugates, or compositions. The enynes may be useful in preparing the conjugates. The end-functionalized polymers may be useful in preparing the conjugates. The conjugates comprise at least (1) A ¹ , which is a peptide, protein, nucleoprotein, mucoprotein lipoprotein glycoprotein or polynucleotide; and (2) B ¹ which is a polymer wherein each instance of the polymer comprises independently one or more pharmaceutical agents (e.g., a drug). In certain embodiments, A ¹ is an antibody, B ¹ is a brush polymer, and the conjugate is an antibody-brush polymer conjugate (ABC). The conjugates may be useful in delivering a pharmaceutical agent to a subject in need thereof or cell. The delivering may be targeted delivering at least because the peptide, protein, nucleoprotein, mucoprotein, lipoprotein, glycoprotein, or polynucleotide selectively binds a target organ or target tissue in the subject in need thereof. The conjugates may be useful in treating, preventing, or diagnosing a disease. The conjugates may be advantageous over the pharmaceutical agent because the former may show higher potency, efficacy, bioavailability, safety, and/or subject compliance; wider therapeutic window; fewer and/or less severe side effects; and/or lower toxicity and/or resistance to treatment than the latter. One or more of the advantages may be at least in part because the peptide, protein, nucleoprotein, mucoprotein, lipoprotein, glycoprotein, or polynucleotide selectively binds a target (e.g., a target peptide, target protein, target nucleoprotein, target mucoprotein, target lipoprotein, target glycoprotein, target polynucleotide, target cell, target issue, target organ) that is associated with the disease. The conjugates may be advantageous over known antibody-drug conjugates (ADCs) because the former: (1) may show higher drug-to- antibody ratios (DARs); (2) may be applicable to a broader range of pharmaceutical agents; (3) may be applicable to pharmaceutical agents with lower limitations on the pharmaceutical agents’ potency and/or hydrophilicity; (4) may have a more general synthesis strategy for different pharmaceutical agents; (5) may show long circulation times (e.g., at least because of the higher protection by the brush chains (e.g., PEG); and/or (6) may have a more controllable release of the pharmaceutical agents (e.g., at least because of the linkers (e.g., L)). DEFINITIONS Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein should be understood as modified in all instances by the term “about.” "About" and "approximately" shall generally mean an acceptable degree of error for the quantity measured given the nature or precision of the measurements. Exemplary degrees of error are within 20 percent (%), typically, within 10%, and more typically, within 5%, 4%, 3%, 2% or 1% of a given value or range of values. Definitions of specific functional groups and chemical terms are described in more detail below. The chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75 ^th Ed., inside cover, and specific functional groups are generally defined as described therein. Additionally, general principles of organic chemistry as well as specific functional moieties and reactivity are described in Organic Chemistry, Thomas Sorrell, University Science Books, Sausalito, 1999; Smith and March March’s Advanced Organic Chemistry, 5 ^th Edition, John Wiley & Sons, Inc., New York, 2001; Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., New York, 1989; and Carruthers, Some Modern Methods of Organic Synthesis, 3 ^rd Edition, Cambridge University Press, Cambridge, 1987. Compounds described herein can comprise one or more asymmetric centers, and thus can exist in various stereoisomeric forms, e.g., enantiomers and/or diastereomers. For example, the compounds described herein can be in the form of an individual enantiomer, diastereomer or geometric isomer, or can be in the form of a mixture of stereoisomers, including racemic mixtures and mixtures enriched in one or more stereoisomer. Isomers can be isolated from mixtures by methods known to those skilled in the art, including chiral high pressure liquid chromatography (HPLC) and the formation and crystallization of chiral salts; or preferred isomers can be prepared by asymmetric syntheses. See, for example, Jacques et al., Enantiomers, Racemates and Resolutions (Wiley Interscience, New York, 1981); Wilen et al., Tetrahedron 33:2725 (1977); Eliel, E.L. Stereochemistry of Carbon Compounds (McGraw–Hill, NY, 1962); and Wilen, S.H. Tables of Resolving Agents and Optical Resolutions p.268 (E.L. Eliel, Ed., Univ. of Notre Dame Press, Notre Dame, IN 1972). The invention additionally encompasses compounds as individual isomers substantially free of other isomers, and alternatively, as mixtures of various isomers. When a range of values (“range”) is listed, it is intended to encompass each value and sub–range within the range. A range is inclusive of the values at the two ends of the range unless otherwise provided. For example, “an integer between 1 and 4” refers to 1, 2, 3, and 4. For example “C1–6 alkyl” is intended to encompass, C1, C2, C3, C4, C5, C6, C1–6, C1–5, C1–4, C1–3, C1–2, C _2–6 , C _2–5 , C _2–4 , C _2–3 , C _3–6 , C _3–5 , C _3–4 , C _4–6 , C _4–5 , and C _5–6 alkyl. The term “alkyl” refers to a radical of a C1-C1000 straight–chain or branched saturated hydrocarbon group. In some embodiments, an alkyl group has 3 to 400 carbon atoms (“C3-C400 alkyl”), 20 to 200 carbon atoms (“C ₂₀ -C ₂₀₀ alkyl”), 1 to 20 carbon atoms (“C ₁ -C ₂₀ alkyl”), 1 to 10 carbon atoms (“C1-C10 alkyl”), 1 to 9 carbon atoms (“C1-C9 alkyl”), 1 to 8 carbon atoms (“C1-C8 alkyl”), 1 to 7 carbon atoms (“C1-C7 alkyl”), 1 to 6 carbon atoms (“C1-C6 alkyl”), 1 to 5 carbon atoms (“C ₁ -C ₅ alkyl”), 1 to 4 carbon atoms (“C ₁ -C ₄ alkyl”), 1 to 3 carbon atoms (“C ₁ -C ₃ alkyl”), 1 to 2 carbon atoms (“C ₁ -C ₂ alkyl”), or 1 carbon atom (“C ₁ alkyl”). Examples of C ₁ -C ₆ alkyl groups include methyl (C1), ethyl (C2), n–propyl (C3), isopropyl (C3), n–butyl (C4), tert–butyl (C4), sec–butyl (C4), iso–butyl (C4), n–pentyl (C5), 3–pentanyl (C5), amyl (C5), neopentyl (C5), 3– methyl–2–butanyl (C ₅ ), tertiary amyl (C ₅ ), and n–hexyl (C ₆ ). Additional examples of alkyl groups include n heptyl (C7) n octyl (C8) and the like C30 C1000 alkyl may be obtained from polymerization. Unless otherwise specified, each instance of an alkyl group is independently unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents. The term “alkenyl” refers to a radical of a straight–chain or branched hydrocarbon group having from 2 to 1000 carbon atoms and one or more carbon-carbon double bonds (e.g., 1, 2, 3, or 4 double bonds). In some embodiments, an alkenyl group has 2 to 400 carbon atoms (“C2–400 alkenyl”) or 20 to 200 carbon atoms (“C ₂₀ -C ₂₀₀ alkenyl”). In some embodiments, an alkenyl group has 2 to 20 carbon atoms (“C2–20 alkenyl”). In some embodiments, an alkenyl group has 2 to 9 carbon atoms (“C2–9 alkenyl”). In some embodiments, an alkenyl group has 2 to 8 carbon atoms (“C _2–8 alkenyl”). In some embodiments, an alkenyl group has 2 to 7 carbon atoms (“C _2–7 alkenyl”). In some embodiments, an alkenyl group has 2 to 6 carbon atoms (“C _2–6 alkenyl”). In some embodiments, an alkenyl group has 2 to 5 carbon atoms (“C2–5 alkenyl”). In some embodiments, an alkenyl group has 2 to 4 carbon atoms (“C2–4 alkenyl”). In some embodiments, an alkenyl group has 2 to 3 carbon atoms (“C _2–3 alkenyl”). In some embodiments, an alkenyl group has 2 carbon atoms (“C2 alkenyl”). The one or more carbon–carbon double bonds can be internal (such as in 2–butenyl) or terminal (such as in 1–butenyl). Examples of C2–4 alkenyl groups include ethenyl (C ₂ ), 1–propenyl (C ₃ ), 2–propenyl (C ₃ ), 1–butenyl (C ₄ ), 2–butenyl (C ₄ ), butadienyl (C4), and the like. Examples of C2–6 alkenyl groups include the aforementioned C2–4 alkenyl groups as well as pentenyl (C5), pentadienyl (C5), hexenyl (C6), and the like. C30-C1000 alkenyl may be obtained from polymerization. Unless otherwise specified, each instance of an alkenyl group is independently unsubstituted (an “unsubstituted alkenyl”) or substituted (a “substituted alkenyl”) with one or more substituents. In an alkenyl group, a C=C double bond for which the stereochemistry is not specified (e.g., –CH=CHCH ₃ , may be in the (E)- or (Z)-configuration. The term “alkynyl” refers to a radical of a straight–chain or branched hydrocarbon group having from 2 to 1000 carbon atoms and one or more carbon-carbon triple bonds (e.g., 1, 2, 3, or 4 triple bonds) (“C _2–10 alkynyl”). In some embodiments, an alkynyl group has 2 to 400 carbon atoms (“C2–400 alkynyl”), 20 to 200 carbon atoms (“C20-C200 alkynyl”), 2 to 20 carbon atoms (“C2–20 alkynyl”), 2 to 9 carbon atoms (“C2–9 alkynyl”), 2 to 8 carbon atoms (“C2–8 alkynyl”), 2 to 7 carbon atoms (“C _2–7 alkynyl”), 2 to 6 carbon atoms (“C _2–6 alkynyl”), 2 to 5 carbon atoms (“C _2–5 alkynyl”), 2 to 4 carbon atoms (“C2–4 alkynyl”), 2 to 3 carbon atoms (“C2–3 alkynyl”), or 2 carbon atoms (“C2 alkynyl”). The one or more carbon–carbon triple bonds can be internal (such as in 2– butynyl) or terminal (such as in 1–butynyl). Examples of C _2–4 alkynyl groups include, without limitation, ethynyl (C2), 1–propynyl (C3), 2–propynyl (C3), 1–butynyl (C4), 2–butynyl (C4), and the like. Examples of C _2–6 alkenyl groups include the aforementioned C _2–4 alkynyl groups as well as pentynyl (C5), hexynyl (C6), and the like. C30-C1000 alkynyl may be obtained from polymerization. Unless otherwise specified, each instance of an alkynyl group is independently unsubstituted (an “unsubstituted alkynyl”) or substituted (a “substituted alkynyl”) with one or more substituents. The term “heteroalkyl” refers to an alkyl group which further includes at least one heteroatom (e.g., 1, 2, 3, 4, or more heteroatoms, as valency permits) selected from oxygen, nitrogen, phosphorus, or sulfur within (i.e., inserted between adjacent carbon atoms of) and/or placed at one or more terminal position(s) of the parent chain. In certain embodiments, a heteroalkyl group refers to a saturated group having from 1 to 1000 carbon atoms and 1 or more heteroatoms within the parent chain (“C _1– C ₁₀₀₀ heteroalkyl” or “C _1–1000 heteroalkyl”), 2 to 400 carbon atoms and 1 or more heteroatoms within the parent chain (“C2–C400 heteroalkyl”), 1 to 20 carbon atoms and 1 or more heteroatoms within the parent chain (“C1–C20 heteroalkyl”), 1 to 10 carbon atoms and 1 or more heteroatoms within the parent chain (“C _1– C ₁₀ heteroalkyl”), 1 to 9 carbon atoms and 1 or more heteroatoms within the parent chain (“C1–C9 heteroalkyl”), 1 to 8 carbon atoms and 1 or more heteroatoms within the parent chain (“C1–C8 heteroalkyl”), 1 to 7 carbon atoms and 1 or more heteroatoms within the parent chain (“C _1– C ₇ heteroalkyl”), 1 to 6 carbon atoms and 1 or more heteroatoms within the parent chain (“C1–C6 heteroalkyl”), 1 to 5 carbon atoms and 1 or more heteroatoms within the parent chain (“C1–C5 heteroalkyl”), 1 to 4 carbon atoms and 1or more heteroatoms within the parent chain (“C _1– C ₄ heteroalkyl”), 1 to 3 carbon atoms and 1 or more heteroatoms within the parent chain (“C _1– C ₃ heteroalkyl”), 1 to 2 carbon atoms and 1 heteroatom within the parent chain (“C1–C2 heteroalkyl”), or 1 carbon atom and 1 heteroatom (“C1 heteroalkyl”). C30-C1000 heteroalkyl may be obtained from polymerization. Unless otherwise specified, each instance of a heteroalkyl group is independently unsubstituted (an “unsubstituted heteroalkyl”) or substituted (a “substituted heteroalkyl”) with one or more substituents. The term “heteroalkenyl” refers to an alkenyl group, which further includes at least one heteroatom (e.g., 1, 2, 3, 4, or more heteroatoms, as valency permits) selected from oxygen, nitrogen, or sulfur within (i.e., inserted between adjacent carbon atoms of) and/or placed at one or more terminal position(s) of the parent chain. In certain embodiments, a heteroalkenyl group refers to a group having from 2 to 1000 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC2–1000 alkenyl” or “C2–1000 heteroalkenyl”), or 40 to 400 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC _40–400 alkenyl”). In certain embodiments, a heteroalkenyl group refers to a group having from 2 to 20 carbon atoms at least one double bond and 1 or more heteroatoms within the parent chain (“heteroC _2–20 alkenyl”). In certain embodiments, a heteroalkenyl group refers to a group having from 2 to 10 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC2–10 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 9 carbon atoms at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC2–9 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 8 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC2–8 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 7 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC2–7 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 6 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC _2–6 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 5 carbon atoms, at least one double bond, and 1 or 2 heteroatoms within the parent chain (“heteroC2–5 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 4 carbon atoms, at least one double bond, and 1or 2 heteroatoms within the parent chain (“heteroC _2–4 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 3 carbon atoms, at least one double bond, and 1 heteroatom within the parent chain (“heteroC2–3 alkenyl”). In some embodiments, a heteroalkenyl group has 2 to 6 carbon atoms, at least one double bond, and 1 or 2 heteroatoms within the parent chain (“heteroC _2–6 alkenyl”). C ₃₀ -C ₁₀₀₀ heteroalkenyl may be obtained from polymerization. Unless otherwise specified, each instance of a heteroalkenyl group is independently unsubstituted (an “unsubstituted heteroalkenyl”) or substituted (a “substituted heteroalkenyl”) with one or more substituents. In certain embodiments, the heteroalkenyl group is an unsubstituted heteroC _2–10 alkenyl. In certain embodiments, the heteroalkenyl group is a substituted heteroC2–10 alkenyl. The term “heteroalkynyl” refers to an alkynyl group, which further includes at least one heteroatom (e.g., 1, 2, 3, 4, or more heteroatoms, as valency permits) selected from oxygen, nitrogen, or sulfur within (i.e., inserted between adjacent carbon atoms of) and/or placed at one or more terminal position(s) of the parent chain. In certain embodiments, a heteroalkynyl group refers to a group having from 2 to 1000 carbon atoms, at least one triple bond, and 1 or more heteroatoms within the parent chain (“heteroC2–1000 alkynyl” or “C2–1000 heteroalkynyl”), or 40 to 400 carbon atoms, at least one double bond, and 1 or more heteroatoms within the parent chain (“heteroC _40–400 alkynyl”). In certain embodiments, a heteroalkynyl group refers to a group having from 2 to 20 carbon atoms, at least one triple bond, and 1 or more heteroatoms within the parent chain (“heteroC2–20 alkynyl”). In certain embodiments, a heteroalkynyl group refers to a group having from 2 to 10 carbon atoms, at least one triple bond, and 1 or more heteroatoms within the parent chain (“heteroC _2–10 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 9 carbon atoms at least one triple bond and 1 or more heteroatoms within the parent chain (“heteroC _2–9 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 8 carbon atoms, at least one triple bond, and 1 or more heteroatoms within the parent chain (“heteroC2–8 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 7 carbon atoms, at least one triple bond, and 1 or more heteroatoms within the parent chain (“heteroC _2–7 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 6 carbon atoms, at least one triple bond, and 1 or more heteroatoms within the parent chain (“heteroC2–6 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 5 carbon atoms, at least one triple bond, and 1 or 2 heteroatoms within the parent chain (“heteroC2–5 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 4 carbon atoms, at least one triple bond, and 1or 2 heteroatoms within the parent chain (“heteroC _2–4 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 3 carbon atoms, at least one triple bond, and 1 heteroatom within the parent chain (“heteroC _2–3 alkynyl”). In some embodiments, a heteroalkynyl group has 2 to 6 carbon atoms, at least one triple bond, and 1 or 2 heteroatoms within the parent chain (“heteroC2–6 alkynyl”). C30-C1000 heteroalkynyl may be obtained from polymerization. Unless otherwise specified, each instance of a heteroalkynyl group is independently unsubstituted (an “unsubstituted heteroalkynyl”) or substituted (a “substituted heteroalkynyl”) with one or more substituents. In certain embodiments, the heteroalkynyl group is an unsubstituted heteroC _2–10 alkynyl. In certain embodiments, the heteroalkynyl group is a substituted heteroC2–10 alkynyl. The term “carbocyclyl” or “carbocyclic” or “cycloalkyl” refers to a radical of a non– aromatic cyclic hydrocarbon group having from 3 to 10 ring carbon atoms (“C _3–10 carbocyclyl”) and zero heteroatoms in the non–aromatic ring system. In some embodiments, a carbocyclyl group has 3 to 8 ring carbon atoms (“C3–8 carbocyclyl”), 3 to 7 ring carbon atoms (“C3–7 carbocyclyl”), 3 to 6 ring carbon atoms (“C3–6 carbocyclyl”), 4 to 6 ring carbon atoms (“C4–6 carbocyclyl”), 5 to 6 ring carbon atoms (“C _5–6 carbocyclyl”), or 5 to 10 ring carbon atoms (“C _5–10 carbocyclyl”). Exemplary C3–6 carbocyclyl groups include, without limitation, cyclopropyl (C3), cyclopropenyl (C3), cyclobutyl (C4), cyclobutenyl (C4), cyclopentyl (C5), cyclopentenyl (C5), cyclohexyl (C ₆ ), cyclohexenyl (C ₆ ), cyclohexadienyl (C ₆ ), and the like. Exemplary C _3–8 carbocyclyl groups include, without limitation, the aforementioned C3–6 carbocyclyl groups as well as cycloheptyl (C7), cycloheptenyl (C7), cycloheptadienyl (C7), cycloheptatrienyl (C7), cyclooctyl (C ₈ ), cyclooctenyl (C ₈ ), bicyclo[2.2.1]heptanyl (C ₇ ), bicyclo[2.2.2]octanyl (C ₈ ), and the like. Exemplary C _3–10 carbocyclyl groups include, without limitation, the aforementioned C _3–8 carbocyclyl groups as well as cyclononyl (C9), cyclononenyl (C9), cyclodecyl (C10), cyclodecenyl (C10), octahydro–1H–indenyl (C9), decahydronaphthalenyl (C10), spiro[4.5]decanyl (C10), and the like. As the foregoing examples illustrate, in certain embodiments, the carbocyclyl group is either monocyclic (“monocyclic carbocyclyl”) or polycyclic (eg containing a fused bridged or spiro ring system such as a bicyclic system (“bicyclic carbocyclyl”) or tricyclic system (“tricyclic carbocyclyl”)) and can be saturated or can contain one or more carbon–carbon double or triple bonds. “Carbocyclyl” also includes ring systems wherein the carbocyclyl ring, as defined above, is fused with one or more aryl or heteroaryl groups wherein the point of attachment is on the carbocyclyl ring, and in such instances, the number of carbons continue to designate the number of carbons in the carbocyclic ring system. Unless otherwise specified, each instance of a carbocyclyl group is independently unsubstituted (an “unsubstituted carbocyclyl”) or substituted (a “substituted carbocyclyl”) with one or more substituents. The term “heterocyclyl” or “heterocyclic” refers to a radical of a 3– to 14–membered non–aromatic ring system having ring carbon atoms and 1 to 4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, phosphorus, and sulfur (“3–14 membered heterocyclyl”). In heterocyclyl groups that contain one or more nitrogen atoms, the point of attachment can be a carbon or nitrogen atom, as valency permits. A heterocyclyl group can either be monocyclic (“monocyclic heterocyclyl”) or polycyclic (e.g., a fused, bridged or spiro ring system such as a bicyclic system (“bicyclic heterocyclyl”) or tricyclic system (“tricyclic heterocyclyl”)), and can be saturated or can contain one or more carbon–carbon double or triple bonds. Heterocyclyl polycyclic ring systems can include one or more heteroatoms in one or both rings. “Heterocyclyl” also includes ring systems wherein the heterocyclyl ring, as defined above, is fused with one or more carbocyclyl groups wherein the point of attachment is either on the carbocyclyl or heterocyclyl ring, or ring systems wherein the heterocyclyl ring, as defined above, is fused with one or more aryl or heteroaryl groups, wherein the point of attachment is on the heterocyclyl ring, and in such instances, the number of ring members continue to designate the number of ring members in the heterocyclyl ring system. Unless otherwise specified, each instance of heterocyclyl is independently unsubstituted (an “unsubstituted heterocyclyl”) or substituted (a “substituted heterocyclyl”) with one or more substituents. In some embodiments, a heterocyclyl group is a 5–10 membered non–aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, phosphorus, and sulfur (“5–10 membered heterocyclyl”). In some embodiments, a heterocyclyl group is a 5–8 membered non–aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen, oxygen, phosphorus, and sulfur (“5–8 membered heterocyclyl”). In some embodiments, a heterocyclyl group is a 5–6 membered non–aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms, wherein each heteroatom is independently selected from nitrogen oxygen phosphorus and sulfur (“5 6 membered heterocyclyl”). In some embodiments, the 5–6 membered heterocyclyl has 1–3 ring heteroatoms selected from nitrogen, oxygen, phosphorus, and sulfur. In some embodiments, the 5–6 membered heterocyclyl has 1–2 ring heteroatoms selected from nitrogen, oxygen, phosphorus, and sulfur. In some embodiments, the 5–6 membered heterocyclyl has 1 ring heteroatom selected from nitrogen, oxygen, phosphorus, and sulfur. Exemplary 3–membered heterocyclyl groups containing 1 heteroatom include, without limitation, azirdinyl, oxiranyl, and thiiranyl. Exemplary 4–membered heterocyclyl groups containing 1 heteroatom include, without limitation, azetidinyl, oxetanyl and thietanyl. Exemplary 5–membered heterocyclyl groups containing 1 heteroatom include, without limitation, tetrahydrofuranyl, dihydrofuranyl, tetrahydrothiophenyl, dihydrothiophenyl, pyrrolidinyl, dihydropyrrolyl, and pyrrolyl–2,5–dione. Exemplary 5–membered heterocyclyl groups containing 2 heteroatoms include, without limitation, dioxolanyl, oxathiolanyl and dithiolanyl. Exemplary 5–membered heterocyclyl groups containing 3 heteroatoms include, without limitation, triazolinyl, oxadiazolinyl, and thiadiazolinyl. Exemplary 6–membered heterocyclyl groups containing 1 heteroatom include, without limitation, piperidinyl, tetrahydropyranyl, dihydropyridinyl, and thianyl. Exemplary 6–membered heterocyclyl groups containing 2 heteroatoms include, without limitation, piperazinyl, morpholinyl, dithianyl, and dioxanyl. Exemplary 6–membered heterocyclyl groups containing 3 heteroatoms include, without limitation, triazinanyl. Exemplary 7–membered heterocyclyl groups containing 1 heteroatom include, without limitation, azepanyl, oxepanyl, and thiepanyl. Exemplary 8– membered heterocyclyl groups containing 1 heteroatom include, without limitation, azocanyl, oxecanyl and thiocanyl. Exemplary bicyclic heterocyclyl groups include, without limitation, indolinyl, isoindolinyl, dihydrobenzofuranyl, dihydrobenzothienyl, tetrahydrobenzothienyl, tetrahydrobenzofuranyl, tetrahydroindolyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl, decahydroisoquinolinyl, octahydrochromenyl, octahydroisochromenyl, decahydronaphthyridinyl, decahydro–1,8–naphthyridinyl, octahydropyrrolo[3,2–b]pyrrole, indolinyl, phthalimidyl, naphthalimidyl, chromanyl, chromenyl, 1H–benzo[e][1,4]diazepinyl, 1,4,5,7–tetrahydropyrano[3,4–b]pyrrolyl, 5,6–dihydro–4H–furo[3,2–b]pyrrolyl, 6,7–dihydro– 5H–furo[3,2–b]pyranyl, 5,7–dihydro–4H–thieno[2,3–c]pyranyl, 2,3–dihydro–1H–pyrrolo[2,3– b]pyridinyl, 2,3–dihydrofuro[2,3–b]pyridinyl, 4,5,6,7–tetrahydro–1H–pyrrolo[2,3–b]pyridinyl, 4,5,6,7–tetrahydrofuro[3,2–c]pyridinyl, 4,5,6,7–tetrahydrothieno[3,2–b]pyridinyl, 1,2,3,4– tetrahydro–1,6–naphthyridinyl, and the like. The term “aryl” refers to a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 pi electrons shared in a cyclic array) having 6 14 ring carbon atoms and zero heteroatoms provided in the aromatic ring system (“C _6–14 aryl”). In some embodiments, an aryl group has 6 ring carbon atoms (“C ₆ aryl”; e.g., phenyl). In some embodiments, an aryl group has 10 ring carbon atoms (“C10 aryl”; e.g., naphthyl such as 1–naphthyl and 2–naphthyl). In some embodiments, an aryl group has 14 ring carbon atoms (“C ₁₄ aryl”; e.g., anthracyl). “Aryl” also includes ring systems wherein the aryl ring, as defined above, is fused with one or more carbocyclyl or heterocyclyl groups wherein the radical or point of attachment is on the aryl ring, and in such instances, the number of carbon atoms continue to designate the number of carbon atoms in the aryl ring system. Unless otherwise specified, each instance of an aryl group is independently unsubstituted (an “unsubstituted aryl”) or substituted (a “substituted aryl”) with one or more substituents. The term “heteroaryl” refers to a radical of a 5–14 membered monocyclic or polycyclic (e.g., bicyclic, tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 pi electrons shared in a cyclic array) having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–14 membered heteroaryl”). In heteroaryl groups that contain one or more nitrogen atoms, the point of attachment can be a carbon or nitrogen atom, as valency permits. Heteroaryl polycyclic ring systems can include one or more heteroatoms in one or both rings. “Heteroaryl” includes ring systems wherein the heteroaryl ring, as defined above, is fused with one or more carbocyclyl or heterocyclyl groups wherein the point of attachment is on the heteroaryl ring, and in such instances, the number of ring members continue to designate the number of ring members in the heteroaryl ring system. “Heteroaryl” also includes ring systems wherein the heteroaryl ring, as defined above, is fused with one or more aryl groups wherein the point of attachment is either on the aryl or heteroaryl ring, and in such instances, the number of ring members designates the number of ring members in the fused polycyclic (aryl/heteroaryl) ring system. Polycyclic heteroaryl groups wherein one ring does not contain a heteroatom (e.g., indolyl, quinolinyl, carbazolyl, and the like) the point of attachment can be on either ring, i.e., either the ring bearing a heteroatom (e.g., 2–indolyl) or the ring that does not contain a heteroatom (e.g., 5– indolyl). A heteroaryl group be monovalent or may have more than one point of attachment to another moiety (e.g., it may be divalent, trivalent, etc), although the valency may be specified directly in the name of the group. For example, “triazoldiyl” refers to a divalent triazolyl moiety. In some embodiments, a heteroaryl group is a 5–10 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–10 membered heteroaryl”). In some embodiments, a heteroaryl group is a 5–8 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system wherein each heteroatom is independently selected from nitrogen oxygen and sulfur (“5–8 membered heteroaryl”). In some embodiments, a heteroaryl group is a 5–6 membered aromatic ring system having ring carbon atoms and 1–4 ring heteroatoms provided in the aromatic ring system, wherein each heteroatom is independently selected from nitrogen, oxygen, and sulfur (“5–6 membered heteroaryl”). In some embodiments, the 5–6 membered heteroaryl has 1–3 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5–6 membered heteroaryl has 1–2 ring heteroatoms selected from nitrogen, oxygen, and sulfur. In some embodiments, the 5–6 membered heteroaryl has 1 ring heteroatom selected from nitrogen, oxygen, and sulfur. Unless otherwise specified, each instance of a heteroaryl group is independently unsubstituted (an “unsubstituted heteroaryl”) or substituted (a “substituted heteroaryl”) with one or more substituents. Exemplary 5–membered heteroaryl groups containing 1 heteroatom include, without limitation, pyrrolyl, furanyl, and thiophenyl. Exemplary 5–membered heteroaryl groups containing 2 heteroatoms include, without limitation, imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, and isothiazolyl. Exemplary 5–membered heteroaryl groups containing 3 heteroatoms include, without limitation, triazolyl, oxadiazolyl, and thiadiazolyl. Exemplary 5–membered heteroaryl groups containing 4 heteroatoms include, without limitation, tetrazolyl. Exemplary 6– membered heteroaryl groups containing 1 heteroatom include, without limitation, pyridinyl. Exemplary 6–membered heteroaryl groups containing 2 heteroatoms include, without limitation, pyridazinyl, pyrimidinyl, and pyrazinyl. Exemplary 6–membered heteroaryl groups containing 3 or 4 heteroatoms include, without limitation, triazinyl and tetrazinyl, respectively. Exemplary 7– membered heteroaryl groups containing 1 heteroatom include, without limitation, azepinyl, oxepinyl, and thiepinyl. Exemplary 5,6–bicyclic heteroaryl groups include, without limitation, indolyl, isoindolyl, indazolyl, benzotriazolyl, benzothiophenyl, isobenzothiophenyl, benzofuranyl, benzoisofuranyl, benzimidazolyl, benzoxazolyl, benzisoxazolyl, benzoxadiazolyl, benzthiazolyl, benzisothiazolyl, benzthiadiazolyl, indolizinyl, and purinyl. Exemplary 6,6– bicyclic heteroaryl groups include, without limitation, naphthyridinyl, pteridinyl, quinolinyl, isoquinolinyl, cinnolinyl, quinoxalinyl, phthalazinyl, and quinazolinyl. Exemplary tricyclic heteroaryl groups include, without limitation, phenanthridinyl, dibenzofuranyl, carbazolyl, acridinyl, phenothiazinyl, phenoxazinyl and phenazinyl. As understood from the above, alkyl, alkenyl, alkynyl, carbocyclyl, aryl, and heteroaryl groups are, in certain embodiments, optionally substituted. Optionally substituted refers to a group which may be substituted or unsubstituted (e.g., “substituted” or “unsubstituted” alkyl). In general, the term “substituted” means that at least one hydrogen present on a group is replaced with a permissible substituent, e.g., a substituent which upon substitution results in a stable compound eg a compound which does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, or other reaction. Unless otherwise indicated, a “substituted” group has a substituent at one or more substitutable positions of the group, and when more than one position in any given structure is substituted, the substituent is either the same or different at each position. The term “substituted” is contemplated to include substitution with all permissible substituents of organic compounds, any of the substituents described herein that results in the formation of a stable compound. The present invention contemplates any and all such combinations in order to arrive at a stable compound. For purposes of this invention, heteroatoms such as nitrogen may have hydrogen substituents and/or any suitable substituent as described herein which satisfy the valencies of the heteroatoms and results in the formation of a stable moiety. Affixing the suffix “ene” to a group indicates the group is a polyvalent (e.g., bivalent, trivalent, tetravalent, or pentavalent) moiety. In certain embodiments, affixing the suffix “ene” to a group indicates the group is a bivalent moiety. Exemplary carbon atom substituents include, but are not limited to, halogen, −CN, −NO ₂ , −N3, −SO2H, −SO3H, −OH, −OR ^aa , −ON(R ^bb )2, −N(R ^bb )2, −N(R ^bb )3 ⁺ X ⁻ , −N(OR ^cc )R ^bb , −SH, −SR ^aa , −SSR ^cc , −C(=O)R ^aa , −CO2H, −CHO, −C(OR ^cc )2, −CO2R ^aa , −OC(=O)R ^aa , −OCO2R ^aa , −C(=O)N(R ^bb ) ₂ , −OC(=O)N(R ^bb ) ₂ , −NR ^bb C(=O)R ^aa , −NR ^bb CO ₂ R ^aa , −NR ^bb C(=O)N(R ^bb ) ₂ , −C(=NR ^bb )R ^aa , −C(=NR ^bb )OR ^aa , −OC(=NR ^bb )R ^aa , −OC(=NR ^bb )OR ^aa , −C(=NR ^bb )N(R ^bb )2, −OC(=NR ^bb )N(R ^bb )2, −NR ^bb C(=NR ^bb )N(R ^bb )2, −C(=O)NR ^bb SO2R ^aa , −NR ^bb SO2R ^aa , −SO2N(R ^bb )2, −SO ₂ R ^aa , −SO ₂ OR ^aa , −OSO ₂ R ^aa , −S(=O)R ^aa , −OS(=O)R ^aa , −Si(R ^aa ) ₃ , −OSi(R ^aa ) ₃ −C(=S)N(R ^bb ) ₂ , −C(=O)SR ^aa , −C(=S)SR ^aa , −SC(=S)SR ^aa , −SC(=O)SR ^aa , −OC(=O)SR ^aa , −SC(=O)OR ^aa , −OP(=O)(N(R ^bb )2)2, −NR ^bb P(=O)(R ^aa )2, −NR ^bb P(=O)(OR ^cc )2, −NR ^bb P(=O)(N(R ^bb )2)2, −P(R ^cc )2, −P(OR ^cc ) ₂ , −P(R ^cc ) ₃ ⁺ X ⁻ , −P(OR ^cc ) ₃ ⁺ X ⁻ , −P(R ^cc ) ₄ , −P(OR ^cc ) ₄ , −OP(R ^cc ) ₂ , −OP(R ^cc ) ₃ ⁺ X ⁻ , −OP(OR ^cc )2, −OP(OR ^cc )3 ⁺ X ⁻ , −OP(R ^cc )4, −OP(OR ^cc )4, −B(R ^aa )2, −B(OR ^cc )2, −BR ^aa (OR ^cc ), C1-10 alkyl, C1-10 perhaloalkyl, C2-10 alkenyl, C2-10 alkynyl, heteroC1-10 alkyl, heteroC2-10 alkenyl, heteroC _2-10 alkynyl, C _3-10 carbocyclyl, 3-14 membered heterocyclyl, C _6-14 aryl, and 5-14 membered heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^dd groups; or two geminal hydrogens on a carbon atom are replaced with the group =O, =S, =NN(R ^bb )2, =NNR ^bb C(=O)R ^aa , =NNR ^bb C(=O)OR ^aa , =NNR ^bb S(=O)2R ^aa , =NR ^bb , or =NOR ^cc ; each instance of R ^aa is, independently, selected from C1-10 alkyl, C1-10 perhaloalkyl, C2-10 alkenyl, C _2-10 alkynyl, heteroC _1-10 alkyl, heteroC _2-10 alkenyl, heteroC _2-10 alkynyl, C _3-10 carbocyclyl, 314 membered heterocyclyl C614 aryl and 514 membered heteroaryl or two R ^aa groups are joined to form a 3-14 membered heterocyclyl or 5-14 membered heteroaryl ring, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^dd groups; each instance of R ^bb is, independently, selected from hydrogen, −OH, −OR ^aa , −N(R ^cc ) ₂ , −CN, −C(=O)R ^aa , −C(=O)N(R ^cc )2, −CO2R ^aa , −SO2R ^aa , −C(=NR ^cc )OR ^aa , −C(=NR ^cc )N(R ^cc )2, −SO2N(R ^cc )2, −SO2R ^cc , −SO2OR ^cc , −SOR ^aa , −C(=S)N(R ^cc )2, −C(=O)SR ^cc , −C(=S)SR ^cc , −P(=O)(R ^aa ) ₂ , −P(=O)(OR ^cc ) ₂ , −P(=O)(N(R ^cc ) ₂ ) ₂ , C _1-10 alkyl, C _1-10 perhaloalkyl, C _2-10 alkenyl, C _2- 10 alkynyl, heteroC1-10alkyl, heteroC2-10alkenyl, heteroC2-10alkynyl, C3-10 carbocyclyl, 3-14 membered heterocyclyl, C6-14 aryl, and 5-14 membered heteroaryl, or two R ^bb groups are joined to form a 3-14 membered heterocyclyl or 5-14 membered heteroaryl ring, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^dd groups; each instance of R ^cc is, independently, selected from hydrogen, C1-10 alkyl, C1-10 perhaloalkyl, C _2-10 alkenyl, C _2-10 alkynyl, heteroC _1-10 alkyl, heteroC _2-10 alkenyl, heteroC _2-10 alkynyl, C3-10 carbocyclyl, 3-14 membered heterocyclyl, C6-14 aryl, and 5-14 membered heteroaryl, or two R ^cc groups are joined to form a 3-14 membered heterocyclyl or 5-14 membered heteroaryl ring, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^dd groups; each instance of R ^dd is, independently, selected from halogen, −CN, −NO ₂ , −N ₃ , −SO ₂ H, −SO ₃ H, −OH, −OR ^ee , −ON(R ^ff ) ₂ , −N(R ^ff ) ₂ , −N(R ^ff ) ₃ ⁺ X ⁻ , −N(OR ^ee )R ^ff , −SH, −SR ^ee , −SSR ^ee , −NR ^ff C(=O)R ^ee , −NR ^ff CO2R ^ee , −NR ^ff C(=O)N(R ^ff )2, −C(=NR ^ff )OR ^ee , −OC(=NR ^ff )R ^ee , −OC(=NR ^ff )OR ^ee , −C(=NR ^ff )N(R ^ff ) ₂ , −OC(=NR ^ff )N(R ^ff ) ₂ , −NR ^ff C(=NR ^ff )N(R ^ff ) ₂ , −NR ^ff SO ₂ R ^ee , −SO2N(R ^ff )2, −SO2R ^ee , −SO2OR ^ee , −OSO2R ^ee , −S(=O)R ^ee , −Si(R ^ee )3, −OSi(R ^ee )3, −C(=S)N(R ^ff )2, −C(=O)SR ^ee , −C(=S)SR ^ee , −SC(=S)SR ^ee , −P(=O)(OR ^ee )2, −P(=O)(R ^ee )2, −OP(=O)(R ^ee )2, −OP(=O)(OR ^ee ) ₂ , C _1-6 alkyl, C _1-6 perhaloalkyl, C _2-6 alkenyl, C _2-6 alkynyl, heteroC _1-6 alkyl, heteroC2-6alkenyl, heteroC2-6alkynyl, C3-10 carbocyclyl, 3-10 membered heterocyclyl, C6-10 aryl, 5-10 membered heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^gg groups, or two geminal R ^dd substituents can be joined to form =O or =S; each instance of R ^ee is, independently, selected from C1-6 alkyl, C1-6 perhaloalkyl, C2-6 alkenyl, C2-6 alkynyl, heteroC1-6 alkyl, heteroC2-6alkenyl, heteroC2-6 alkynyl, C3-10 carbocyclyl, C _6-10 aryl, 3-10 membered heterocyclyl, and 3-10 membered heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^gg groups; each instance of R ^ff is, independently, selected from hydrogen, C1-6 alkyl, C1-6 perhaloalkyl, C _2-6 alkenyl, C _2-6 alkynyl, heteroC _1-6 alkyl, heteroC _2-6 alkenyl, heteroC _2-6 alkynyl, C _3- 10 carbocyclyl, 3-10 membered heterocyclyl, C6-10 aryl and 5-10 membered heteroaryl, or two R ^ff groups are joined to form a 3-10 membered heterocyclyl or 5-10 membered heteroaryl ring, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^gg groups; each instance of R ^gg is, independently, halogen, −CN, −NO2, −N3, −SO2H, −SO3H, −OH, −OC _1-6 alkyl, −ON(C _1-6 alkyl) ₂ , −N(C _1-6 alkyl) ₂ , −N(C _1-6 alkyl) ₃ ⁺ X ⁻ , −NH(C _1-6 alkyl) ₂ ⁺ X ⁻ , −NH ₂ (C _1-6 alkyl) ⁺ X ⁻ , −NH ₃ ⁺ X ⁻ , −N(OC _1-6 alkyl)(C _1-6 alkyl), −N(OH)(C _1-6 alkyl), −NH(OH), −SH, −SC1-6 alkyl, −SS(C1-6 alkyl), −C(=O)(C1-6 alkyl), −CO2H, −CO2(C1-6 alkyl), −OC(=O)(C1- 6 alkyl), −OCO2(C1-6 alkyl), −C(=O)NH2, −C(=O)N(C1-6 alkyl)2, −OC(=O)NH(C1-6 alkyl), −NHC(=O)( C _1-6 alkyl), −N(C _1-6 alkyl)C(=O)( C _1-6 alkyl), −NHCO ₂ (C _1-6 alkyl), −NHC(=O)N(C _1- 6 alkyl)2, −NHC(=O)NH(C1-6 alkyl), −NHC(=O)NH2, −C(=NH)O(C1-6 alkyl), −OC(=NH)(C1-6 alkyl), −OC(=NH)OC1-6 alkyl, −C(=NH)N(C1-6 alkyl)2, −C(=NH)NH(C1-6 alkyl), −C(=NH)NH2, −OC(=NH)N(C _1-6 alkyl) ₂ , −OC(NH)NH(C _1-6 alkyl), −OC(NH)NH ₂ , −NHC(NH)N(C _1-6 alkyl) ₂ , −NHC(=NH)NH2, −NHSO2(C1-6 alkyl), −SO2N(C1-6 alkyl)2, −SO2NH(C1-6 alkyl), −SO2NH2, −SO2C1-6 alkyl, −SO2OC1-6 alkyl, −OSO2C1-6 alkyl, −SOC1-6 alkyl, −Si(C1-6 alkyl)3, −OSi(C1-6 alkyl) ₃ −C(=S)N(C _1-6 alkyl) ₂ , C(=S)NH(C _1-6 alkyl), C(=S)NH ₂ , −C(=O)S(C _1-6 alkyl), −C(=S)SC _{1- 6} alkyl, −SC(=S)SC _1-6 alkyl, −P(=O)(OC _1-6 alkyl) ₂ , −P(=O)(C _1-6 alkyl) ₂ , −OP(=O)(C _1-6 alkyl) ₂ , −OP(=O)(OC1-6 alkyl)2, C1-6 alkyl, C1-6 perhaloalkyl, C2-6 alkenyl, C2-6 alkynyl, heteroC1-6alkyl, heteroC2-6alkenyl, heteroC2-6alkynyl, C3-10 carbocyclyl, C6-10 aryl, 3-10 membered heterocyclyl, 5-10 membered heteroaryl; or two geminal R ^gg substituents can be joined to form =O or =S; and each X ⁻ is a counterion. In certain embodiments, the carbon atom substituents are independently halogen, substituted or unsubstituted, C _1-6 alkyl, −OR ^aa , −SR ^aa , −N(R ^bb ) ₂ , –CN, –SCN, –NO ₂ , −C(=O)R ^aa , −CO2R ^aa , −C(=O)N(R ^bb )2, −OC(=O)R ^aa , −OCO2R ^aa , −OC(=O)N(R ^bb )2, −NR ^bb C(=O)R ^aa , −NR ^bb CO2R ^aa , or −NR ^bb C(=O)N(R ^bb )2. In certain embodiments, the carbon atom substituents are independently halogen, substituted or unsubstituted, C _1-6 alkyl, −OR ^aa , −SR ^aa , −N(R ^bb ) ₂ , –CN, – SCN, or –NO ₂ . Nitrogen atoms can be substituted or unsubstituted as valency permits, and include primary, secondary, tertiary, and quaternary nitrogen atoms. Exemplary nitrogen atom substituents include, but are not limited to, hydrogen, −OH, −OR ^aa , −N(R ^cc ) ₂ , −CN, −C(=O)R ^aa , −C(=O)N(R ^cc )2, −CO2R ^aa , −SO2R ^aa , −C(=NR ^bb )R ^aa , −C(=NR ^cc )OR ^aa , −C(=NR ^cc )N(R ^cc )2, −SO ₂ N(R ^cc ) ₂ , −SO ₂ R ^cc , −SO ₂ OR ^cc , −SOR ^aa , −C(=S)N(R ^cc ) ₂ , −C(=O)SR ^cc , −C(=S)SR ^cc , −P(=O)(OR ^cc )2, −P(=O)(R ^aa )2, −P(=O)(N(R ^cc )2)2, C1-10 alkyl, C1-10 perhaloalkyl, C2-10 alkenyl, C2- 10 alkynyl, heteroC1-10alkyl, heteroC2-10alkenyl, heteroC2-10alkynyl, C3-10 carbocyclyl, 3-14 membered heterocyclyl, C _6-14 aryl, and 5-14 membered heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^dd groups, and wherein R ^aa , R ^bb , R ^cc and R ^dd are as defined above. In certain embodiments, the substituent present on the nitrogen atom is a nitrogen protecting group (also referred to herein as an “amino protecting group”). Nitrogen protecting groups include, but are not limited to, −OH, −OR ^aa , −N(R ^cc ) ₂ , −C(=O)R ^aa , −C(=O)N(R ^cc ) ₂ , −CO ₂ R ^aa , −SO ₂ R ^aa , −C(=NR ^cc )R ^aa , −C(=NR ^cc )OR ^aa , −C(=NR ^cc )N(R ^cc ) ₂ , −SO ₂ N(R ^cc ) ₂ , −SO ₂ R ^cc , −SO2OR ^cc , −SOR ^aa , −C(=S)N(R ^cc )2, −C(=O)SR ^cc , −C(=S)SR ^cc , C1-10 alkyl (e.g., aralkyl, heteroaralkyl), C2-10 alkenyl, C2-10 alkynyl, heteroC1-10 alkyl, heteroC2-10 alkenyl, heteroC2-10 alkynyl, C _3-10 carbocyclyl, 3-14 membered heterocyclyl, C _6-14 aryl, and 5-14 membered heteroaryl groups, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, carbocyclyl, heterocyclyl, aralkyl, aryl, and heteroaryl is independently substituted with 0, 1, 2, 3, 4, or 5 R ^dd groups, and wherein R ^aa , R ^bb , R ^cc and R ^dd are as defined herein. Nitrogen protecting groups are well known in the art and include those described in detail in Protecting Groups in Organic Synthesis, T. W. Greene and P. G. M. Wuts, 3 ^rd edition, John Wiley & Sons, 1999, incorporated herein by reference. For example, nitrogen protecting groups such as amide groups (e.g., −C(=O)R ^aa ) include, but are not limited to, formamide, acetamide, chloroacetamide, trichloroacetamide, trifluoroacetamide, phenylacetamide, 3-phenylpropanamide, picolinamide, 3- pyridylcarboxamide, N-benzoylphenylalanyl derivative, benzamide, p-phenylbenzamide, o- nitrophenylacetamide, o-nitrophenoxyacetamide, acetoacetamide, (N’- dithiobenzyloxyacylamino)acetamide, 3-(p-hydroxyphenyl)propanamide, 3-(o- nitrophenyl)propanamide, 2-methyl-2-(o-nitrophenoxy)propanamide, 2-methyl-2-(o- phenylazophenoxy)propanamide, 4-chlorobutanamide, 3-methyl-3-nitrobutanamide, o- nitrocinnamide, N-acetylmethionine derivative, o-nitrobenzamide and o- (benzoyloxymethyl)benzamide. Nitrogen protecting groups such as carbamate groups (e.g., −C(=O)OR ^aa ) include, but are not limited to, methyl carbamate, ethyl carbamate, 9-fluorenylmethyl carbamate (Fmoc), 9-(2- sulfo)fluorenylmethyl carbamate, 9-(2,7-dibromo)fluorenylmethyl carbamate, 2,7-di-t-butyl-[9- (10,10-dioxo-10,10,10,10-tetrahydrothioxanthyl)]methyl carbamate (DBD-Tmoc), 4- methoxyphenacyl carbamate (Phenoc) 222 trichloroethyl carbamate (Troc) 2 trimethylsilylethyl carbamate (Teoc), 2-phenylethyl carbamate (hZ), 1-(1-adamantyl)-1- methylethyl carbamate (Adpoc), 1,1-dimethyl-2-haloethyl carbamate, 1,1-dimethyl-2,2- dibromoethyl carbamate (DB-t-BOC), 1,1-dimethyl-2,2,2-trichloroethyl carbamate (TCBOC), 1- methyl-1-(4-biphenylyl)ethyl carbamate (Bpoc), 1-(3,5-di-t-butylphenyl)-1-methylethyl carbamate (t-Bumeoc), 2-(2′- and 4′-pyridyl)ethyl carbamate (Pyoc), 2-(N,N- dicyclohexylcarboxamido)ethyl carbamate, t-butyl carbamate (BOC or Boc), 1-adamantyl carbamate (Adoc), vinyl carbamate (Voc), allyl carbamate (Alloc), 1-isopropylallyl carbamate (Ipaoc), cinnamyl carbamate (Coc), 4-nitrocinnamyl carbamate (Noc), 8-quinolyl carbamate, N- hydroxypiperidinyl carbamate, alkyldithio carbamate, benzyl carbamate (Cbz), p-methoxybenzyl carbamate (Moz), p-nitrobenzyl carbamate, p-bromobenzyl carbamate, p-chlorobenzyl carbamate, 2,4-dichlorobenzyl carbamate, 4-methylsulfinylbenzyl carbamate (Msz), 9- anthrylmethyl carbamate, diphenylmethyl carbamate, 2-methylthioethyl carbamate, 2- methylsulfonylethyl carbamate, 2-(p-toluenesulfonyl)ethyl carbamate, [2-(1,3-dithianyl)]methyl carbamate (Dmoc), 4-methylthiophenyl carbamate (Mtpc), 2,4-dimethylthiophenyl carbamate (Bmpc), 2-phosphonioethyl carbamate (Peoc), 2-triphenylphosphonioisopropyl carbamate (Ppoc), 1,1-dimethyl-2-cyanoethyl carbamate, m-chloro-p-acyloxybenzyl carbamate, p- (dihydroxyboryl)benzyl carbamate, 5-benzisoxazolylmethyl carbamate, 2-(trifluoromethyl)-6- chromonylmethyl carbamate (Tcroc), m-nitrophenyl carbamate, 3,5-dimethoxybenzyl carbamate, o-nitrobenzyl carbamate, 3,4-dimethoxy-6-nitrobenzyl carbamate, phenyl(o-nitrophenyl)methyl carbamate, t-amyl carbamate, S-benzyl thiocarbamate, p-cyanobenzyl carbamate, cyclobutyl carbamate, cyclohexyl carbamate, cyclopentyl carbamate, cyclopropylmethyl carbamate, p- decyloxybenzyl carbamate, 2,2-dimethoxyacylvinyl carbamate, o-(N,N- dimethylcarboxamido)benzyl carbamate, 1,1-dimethyl-3-(N,N-dimethylcarboxamido)propyl carbamate, 1,1-dimethylpropynyl carbamate, di(2-pyridyl)methyl carbamate, 2-furanylmethyl carbamate, 2-iodoethyl carbamate, isobornyl carbamate, isobutyl carbamate, isonicotinyl carbamate, p-(p’-methoxyphenylazo)benzyl carbamate, 1-methylcyclobutyl carbamate, 1- methylcyclohexyl carbamate, 1-methyl-1-cyclopropylmethyl carbamate, 1-methyl-1-(3,5- dimethoxyphenyl)ethyl carbamate, 1-methyl-1-(p-phenylazophenyl)ethyl carbamate, 1-methyl-1- phenylethyl carbamate, 1-methyl-1-(4-pyridyl)ethyl carbamate, phenyl carbamate, p- (phenylazo)benzyl carbamate, 2,4,6-tri-t-butylphenyl carbamate, 4-(trimethylammonium)benzyl carbamate, and 2,4,6-trimethylbenzyl carbamate. Nitrogen protecting groups such as sulfonamide groups (e.g., −S(=O) ₂ R ^aa ) include, but are not limited to, p-toluenesulfonamide (Ts), benzenesulfonamide, 2,3,6-trimethyl-4- methoxybenzenesulfonamide (Mtr), 2,4,6-trimethoxybenzenesulfonamide (Mtb), 2,6-dimethyl-4- methoxybenzenesulfonamide (Pme) 2356 tetramethyl 4 methoxybenzenesulfonamide (Mte) 4-methoxybenzenesulfonamide (Mbs), 2,4,6-trimethylbenzenesulfonamide (Mts), 2,6- dimethoxy-4-methylbenzenesulfonamide (iMds), 2,2,5,7,8-pentamethylchroman-6-sulfonamide (Pmc), methanesulfonamide (Ms), β-trimethylsilylethanesulfonamide (SES), 9- anthracenesulfonamide, 4-(4′,8′-dimethoxynaphthylmethyl)benzenesulfonamide (DNMBS), benzylsulfonamide, trifluoromethylsulfonamide, and phenacylsulfonamide. Other nitrogen protecting groups include, but are not limited to, phenothiazinyl-(10)-acyl derivative, N’-p-toluenesulfonylaminoacyl derivative, N’-phenylaminothioacyl derivative, N- benzoylphenylalanyl derivative, N-acetylmethionine derivative, 4,5-diphenyl-3-oxazolin-2-one, N-phthalimide, N-dithiasuccinimide (Dts), N-2,3-diphenylmaleimide, N-2,5-dimethylpyrrole, N- 1,1,4,4-tetramethyldisilylazacyclopentane adduct (STABASE), 5-substituted 1,3-dimethyl-1,3,5- triazacyclohexan-2-one, 5-substituted 1,3-dibenzyl-1,3,5-triazacyclohexan-2-one, 1-substituted 3,5-dinitro-4-pyridone, N-methylamine, N-allylamine, N-[2-(trimethylsilyl)ethoxy]methylamine (SEM), N-3-acetoxypropylamine, N-(1-isopropyl-4-nitro-2-oxo-3-pyrrolin-3-yl)amine, quaternary ammonium salts, N-benzylamine, N-di(4-methoxyphenyl)methylamine, N-5- dibenzosuberylamine, N-triphenylmethylamine (Tr), N-[(4- methoxyphenyl)diphenylmethyl]amine (MMTr), N-9-phenylfluorenylamine (PhF), N-2,7- dichloro-9-fluorenylmethyleneamine, N-ferrocenylmethylamino (Fcm), N-2-picolylamino N’- oxide, N-1,1-dimethylthiomethyleneamine, N-benzylideneamine, N-p- methoxybenzylideneamine, N-diphenylmethyleneamine, N-[(2-pyridyl)mesityl]methyleneamine, N-(N’,N’-dimethylaminomethylene)amine, N,N’-isopropylidenediamine, N-p- nitrobenzylideneamine, N-salicylideneamine, N-5-chlorosalicylideneamine, N-(5-chloro-2- hydroxyphenyl)phenylmethyleneamine, N-cyclohexylideneamine, N-(5,5-dimethyl-3-oxo-1- cyclohexenyl)amine, N-borane derivative, N-diphenylborinic acid derivative, N- [phenyl(pentaacylchromium- or tungsten)acyl]amine, N-copper chelate, N-zinc chelate, N- nitroamine, N-nitrosoamine, amine N-oxide, diphenylphosphinamide (Dpp), dimethylthiophosphinamide (Mpt), diphenylthiophosphinamide (Ppt), dialkyl phosphoramidates, dibenzyl phosphoramidate, diphenyl phosphoramidate, benzenesulfenamide, o- nitrobenzenesulfenamide (Nps), 2,4-dinitrobenzenesulfenamide, pentachlorobenzenesulfenamide, 2-nitro-4-methoxybenzenesulfenamide, triphenylmethylsulfenamide, and 3-nitropyridinesulfenamide (Npys). In certain embodiments, the substituent present on an oxygen atom is an oxygen protecting group (also referred to herein as an “hydroxyl protecting group”). Oxygen protecting groups include, but are not limited to, −R ^aa , −N(R ^bb )2, −C(=O)SR ^aa , −C(=O)R ^aa , −CO2R ^aa , −C(=O)N(R ^bb )2, −C(=NR ^bb )R ^aa , −C(=NR ^bb )OR ^aa , −C(=NR ^bb )N(R ^bb )2, −S(=O)R ^aa , −SO2R ^aa , Si(R ^aa ) ₃ P(R ^cc ) ₂ P(R ^cc ) ₃ ⁺ X ⁻ P(OR ^cc ) ₂ P(OR ^cc ) ₃ ⁺ X ⁻ P(=O)(R ^aa ) ₂ P(=O)(OR ^cc ) ₂ and −P(=O)(N(R ^bb ) ₂ ) ₂ , wherein X ⁻ , R ^aa , R ^bb , and R ^cc are as defined herein. Oxygen protecting groups are well known in the art and include those described in detail in Protecting Groups in Organic Synthesis, T. W. Greene and P. G. M. Wuts, 3 ^rd edition, John Wiley & Sons, 1999, incorporated herein by reference. Exemplary oxygen protecting groups include, but are not limited to, methyl, methoxylmethyl (MOM), methylthiomethyl (MTM), t-butylthiomethyl, (phenyldimethylsilyl)methoxymethyl (SMOM), benzyloxymethyl (BOM), p- methoxybenzyloxymethyl (PMBM), (4-methoxyphenoxy)methyl (p-AOM), guaiacolmethyl (GUM), t-butoxymethyl, 4-pentenyloxymethyl (POM), siloxymethyl, 2-methoxyethoxymethyl (MEM), 2,2,2-trichloroethoxymethyl, bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl (SEMOR), tetrahydropyranyl (THP), 3-bromotetrahydropyranyl, tetrahydrothiopyranyl, 1- methoxycyclohexyl, 4-methoxytetrahydropyranyl (MTHP), 4-methoxytetrahydrothiopyranyl, 4- methoxytetrahydrothiopyranyl S,S-dioxide, 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin- 4-yl (CTMP), 1,4-dioxan-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl, 2,3,3a,4,5,6,7,7a- octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl, 1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl, 1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-(phenylselenyl)ethyl, t-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl, benzyl (Bn), p-methoxybenzyl, 3,4-dimethoxybenzyl, o- nitrobenzyl, p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, p-phenylbenzyl, 2- picolyl, 4-picolyl, 3-methyl-2-picolyl N-oxido, diphenylmethyl, p,p’-dinitrobenzhydryl, 5- dibenzosuberyl, triphenylmethyl, α-naphthyldiphenylmethyl, p-methoxyphenyldiphenylmethyl, di(p-methoxyphenyl)phenylmethyl, tri(p-methoxyphenyl)methyl, 4-(4’- bromophenacyloxyphenyl)diphenylmethyl, 4,4′,4″-tris(4,5-dichlorophthalimidophenyl)methyl, 4,4′,4″-tris(levulinoyloxyphenyl)methyl, 4,4′,4″-tris(benzoyloxyphenyl)methyl, 3-(imidazol-1- yl)bis(4′,4″-dimethoxyphenyl)methyl, 1,1-bis(4-methoxyphenyl)-1′-pyrenylmethyl, 9-anthryl, 9- (9-phenyl)xanthenyl, 9-(9-phenyl-10-oxo)anthryl, 1,3-benzodithiolan-2-yl, benzisothiazolyl S,S- dioxido, trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), dimethylisopropylsilyl (IPDMS), diethylisopropylsilyl (DEIPS), dimethylthexylsilyl, t- butyldimethylsilyl (TBDMS), t-butyldiphenylsilyl (TBDPS), tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl, diphenylmethylsilyl (DPMS), t-butylmethoxyphenylsilyl (TBMPS), formate, benzoylformate, acetate, chloroacetate, dichloroacetate, trichloroacetate, trifluoroacetate, methoxyacetate, triphenylmethoxyacetate, phenoxyacetate, p-chlorophenoxyacetate, 3- phenylpropionate, 4-oxopentanoate (levulinate), 4,4-(ethylenedithio)pentanoate (levulinoyldithioacetal), pivaloate, adamantoate, crotonate, 4-methoxycrotonate, benzoate, p- phenylbenzoate 246 trimethylbenzoate (mesitoate) methyl carbonate 9 fluorenylmethyl carbonate (Fmoc), ethyl carbonate, 2,2,2-trichloroethyl carbonate (Troc), 2-(trimethylsilyl)ethyl carbonate (TMSEC), 2-(phenylsulfonyl) ethyl carbonate (Psec), 2-(triphenylphosphonio) ethyl carbonate (Peoc), isobutyl carbonate, vinyl carbonate, allyl carbonate, t-butyl carbonate (BOC or Boc), p-nitrophenyl carbonate, benzyl carbonate, p-methoxybenzyl carbonate, 3,4- dimethoxybenzyl carbonate, o-nitrobenzyl carbonate, p-nitrobenzyl carbonate, S-benzyl thiocarbonate, 4-ethoxy-1-napththyl carbonate, methyl dithiocarbonate, 2-iodobenzoate, 4- azidobutyrate, 4-nitro-4-methylpentanoate, o-(dibromomethyl)benzoate, 2- formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl, 4-(methylthiomethoxy)butyrate, 2- (methylthiomethoxymethyl)benzoate, 2,6-dichloro-4-methylphenoxyacetate, 2,6-dichloro-4- (1,1,3,3-tetramethylbutyl)phenoxyacetate, 2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate, isobutyrate, monosuccinoate, (E)-2-methyl-2-butenoate, o- (methoxyacyl)benzoate, α-naphthoate, nitrate, alkyl N,N,N’,N’-tetramethylphosphorodiamidate, alkyl N-phenylcarbamate, borate, dimethylphosphinothioyl, alkyl 2,4-dinitrophenylsulfenate, sulfate, methanesulfonate (mesylate), benzylsulfonate, and tosylate (Ts). In certain embodiments, the substituent present on a sulfur atom is a sulfur protecting group (also referred to as a “thiol protecting group”). Sulfur protecting groups include, but are not limited to, −R ^aa , −N(R ^bb ) ₂ , −C(=O)SR ^aa , −C(=O)R ^aa , −CO ₂ R ^aa , −C(=O)N(R ^bb ) ₂ , −C(=NR ^bb )R ^aa , −C(=NR ^bb )OR ^aa , −C(=NR ^bb )N(R ^bb )2, −S(=O)R ^aa , −SO2R ^aa , −Si(R ^aa )3, −P(R ^cc )2, −P(R ^cc )3 ⁺ X ⁻ , −P(OR ^cc )2, −P(OR ^cc )3 ⁺ X ⁻ , −P(=O)(R ^aa )2, −P(=O)(OR ^cc )2, and −P(=O)(N(R ^bb ) 2)2, wherein R ^aa , R ^bb , and R ^cc are as defined herein. Sulfur protecting groups are well known in the art and include those described in detail in Protecting Groups in Organic Synthesis, T. W. Greene and P. G. M. Wuts, 3 ^rd edition, John Wiley & Sons, 1999, incorporated herein by reference. The term “halo” or “halogen” refers to fluorine (fluoro, –F), chlorine (chloro, –Cl), bromine (bromo, –Br), or iodine (iodo, –I). The term “hydroxyl” or “hydroxy” refers to the group –OH. The term “thiol” or “thio” refers to the group –SH. The term “amine” or “amino” refers to the group –NH– or –NH ₂ . A “counterion” or “anionic counterion” is a negatively charged group associated with a positively charged group in order to maintain electronic neutrality. An anionic counterion may be monovalent (i.e., including one formal negative charge). An anionic counterion may also be multivalent (i.e., including more than one formal negative charge), such as divalent or trivalent. Exemplary counterions include halide ions (e.g., F ^– , Cl ^– , Br ^– , I ^– ), NO3 ^– , ClO4 ^– , OH ^– , H2PO4 ^– , HCO3 ⁻ , HSO4 ^– , sulfonate ions (e.g., methansulfonate, trifluoromethanesulfonate (triflate), p– toluenesulfonate, benzenesulfonate, 10–camphor sulfonate, naphthalene–2–sulfonate, naphthalene 1 sulfonic acid 5 sulfonate ethan 1 sulfonic acid 2 sulfonate and the like) carboxylate ions (e.g., acetate, propanoate, benzoate, glycerate, lactate, tartrate, glycolate, gluconate, and the like), BF4 ⁻ , PF4 ^– , PF6 ^– , AsF6 ^– , SbF6 ^– , B[3,5-(CF3)2C6H3]4] ^– , B(C6F5)4 ⁻ , BPh4 ^– , Al(OC(CF3)3)4 ^– , and carborane anions (e.g., CB11H12 ^– or (HCB11Me5Br6) ^– ). Exemplary counterions which may be multivalent include CO ₃ ²⁻ , HPO ₄ ²⁻ , PO ₄ ³⁻ , B ₄ O ₇ ²⁻ , SO ₄ ²⁻ , S ₂ O ₃ ²⁻ , carboxylate anions (e.g., tartrate, citrate, fumarate, maleate, malate, malonate, gluconate, succinate, glutarate, adipate, pimelate, suberate, azelate, sebacate, salicylate, phthalates, aspartate, glutamate, and the like), and carboranes. In certain embodiments, the counterion is triflate. The term “leaving group” is given its ordinary meaning in the art of synthetic organic chemistry and refers to an atom or a group capable of being displaced by a nucleophile. Examples of suitable leaving groups include halogen (such as F, Cl, Br, or I (iodine)), alkoxycarbonyloxy, aryloxycarbonyloxy, alkanesulfonyloxy, arenesulfonyloxy, alkyl- carbonyloxy (e.g., acetoxy), arylcarbonyloxy, aryloxy, methoxy, N,O-dimethylhydroxylamino, pixyl, and haloformates. In some cases, the leaving group is a sulfonic acid ester, such as toluenesulfonate (tosylate, –OTs), methanesulfonate (mesylate, –OMs), p- bromobenzenesulfonyloxy (brosylate, –OBs), –OS(=O)2(CF2)3CF3 (nonaflate, –ONf), or trifluoromethanesulfonate (triflate, –OTf). In some cases, the leaving group is a brosylate, such as p-bromobenzenesulfonyloxy. In some cases, the leaving group is a nosylate, such as 2- nitrobenzenesulfonyloxy. In some embodiments, the leaving group is a sulfonate-containing group. In some embodiments, the leaving group is a tosylate group. The leaving group may also be a phosphineoxide (e.g., formed during a Mitsunobu reaction) or an internal leaving group such as an epoxide or cyclic sulfate. Other examples of leaving groups are water, ammonia, alcohols, ether moieties, thioether moieties, zinc halides, magnesium moieties, diazonium salts, and copper moieties. The term “small molecule” refers to molecules, whether naturally-occurring or artificially created (e.g., via chemical synthesis) that have a relatively low molecular weight. Typically, a small molecule is an organic compound (i.e., it contains carbon). The small molecule may contain multiple carbon-carbon bonds, stereocenters, and other functional groups (e.g., amines, hydroxyl, carbonyls, and heterocyclic rings, etc.). In certain embodiments, the molecular weight of a small molecule is not more than 2,000 g/mol. In certain embodiments, the molecular weight of a small molecule is not more than 1,500 g/mol. In certain embodiments, the molecular weight of a small molecule is not more than 1,000 g/mol, not more than 900 g/mol, not more than 800 g/mol, not more than 700 g/mol, not more than 600 g/mol, not more than 500 g/mol, not more than 400 g/mol, not more than 300 g/mol, not more than 200 g/mol, or not more than 100 g/mol. In certain embodiments the molecular weight of a small molecule is at least 100 g/mol at least 200 g/mol, at least 300 g/mol, at least 400 g/mol, at least 500 g/mol, at least 600 g/mol, at least 700 g/mol, at least 800 g/mol, or at least 900 g/mol, or at least 1,000 g/mol. Combinations of the above ranges (e.g., at least 200 g/mol and not more than 500 g/mol) are also possible. In certain embodiments, the small molecule is a therapeutically active agent such as a drug (e.g., a molecule approved by the U.S. Food and Drug Administration as provided in the Code of Federal Regulations (C.F.R.)). The small molecule may also be complexed with one or more metal atoms and/or metal ions. In this instance, the small molecule is also referred to as a “small organometallic molecule.” Preferred small molecules are biologically active in that they produce a biological effect in animals, preferably mammals, more preferably humans. Small molecules include radionuclides and imaging agents. In certain embodiments, the small molecule is a drug. Preferably, though not necessarily, the drug is one that has already been deemed safe and effective for use in humans or animals by the appropriate governmental agency or regulatory body. For example, drugs approved for human use are listed by the FDA under 21 C.F.R. §§ 330.5, 331 through 361, and 440 through 460, incorporated herein by reference; drugs for veterinary use are listed by the FDA under 21 C.F.R. §§ 500 through 589, incorporated herein by reference. All listed drugs are considered acceptable for use in accordance with the present invention. The term “polymer” refers to a compound comprising eleven or more covalently connected repeating units. In certain embodiments, a polymer is naturally occurring. In certain embodiments, a polymer is synthetic (e.g., not naturally occurring). In certain embodiments, the number average molecular weight of the polymer (e.g., as determined by gel permeation chromatography) is between 1,000 and 3,000, between 3,000 and 10,000, between 10,000 and 30,000, between 30,000 and 100,000, between 100,000 and 300,000, or between 300,000 and 1,000,000, g/mol, inclusive. In certain embodiments, the dispersity of the polymer is between 1 and 1.2, between 1.2 and 1.5, between 1.5 and 2, between 2 and 4, between 4 and 10, inclusive. A “protein,” “peptide,” or “polypeptide” comprises a polymer of amino acid residues linked together by peptide bonds. The term refers to proteins, polypeptides, and peptides of any size, structure, or function. A protein may refer to an individual protein or a collection of proteins. Proteins preferably contain only natural amino acids, although non-natural amino acids (i.e., compounds that do not occur in nature but that can be incorporated into a polypeptide chain) and/or amino acid analogs as are known in the art may alternatively be employed. In certain embodiments, the amino acid residues of a peptide are alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and/or valine, in D and/or L form In certain embodiments the amino acid residues of a peptide are alanine arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and/or valine, in L form. One or more of the amino acids in a protein may be protected. Also, one or more of the amino acids in a protein may be modified, for example, by the addition of a chemical entity such as a carbohydrate group, a hydroxyl group, a phosphate group, a farnesyl group, an isofarnesyl group, a fatty acid group, a linker for conjugation or functionalization, or other modification. A protein may also be a single molecule or may be a multi-molecular complex. A protein may be a fragment of a naturally occurring protein or peptide. A protein may be naturally occurring, recombinant, synthetic, or any combination of these. In certain embodiments, a protein comprises (e.g., consists essentially of) between 3 and 10, between 10 and 30, between 30 and 100, between 100 and 300, between 300 and 1,000, between 1,000 and 3,000, or between 3,000 and 10,000, inclusive, amino acids. In certain embodiments, the amino acids in a protein are natural amino acids. In certain embodiments, the amino acids in a protein are unnatural amino acids. In certain embodiments, the amino acids in a protein are a combination of natural amino acids and unnatural amino acids (e.g., unnatural alpha-amino acids). The term “salt” refers to ionic compounds that result from the neutralization reaction of an acid and a base. A salt is composed of one or more cations (positively charged ions) and one or more anions (negative ions) so that the salt is electrically neutral (without a net charge). Salts of the compounds of this invention include those derived from inorganic and organic acids and bases. Examples of acid addition salts are salts of an amino group formed with inorganic acids such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, and perchloric acid, or with organic acids such as acetic acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, or malonic acid or by using other methods known in the art such as ion exchange. Other salts include adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, hydroiodide, 2–hydroxy–ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2– naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3–phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, valerate salts, and the like. Salts derived from appropriate bases include alkali metal, alkaline earth metal, ammonium and N ⁺ (C1-4 alkyl)4 salts. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like. Further salts include ammonium, quaternary ammonium, and amine cations formed using counterions such as halide, hydroxide, carboxylate, sulfate, phosphate, nitrate, lower alkyl sulfonate, and aryl sulfonate. The term “pharmaceutically acceptable salt” refers to those salts which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response, and the like, and are commensurate with a reasonable benefit/risk ratio. Pharmaceutically acceptable salts are well known in the art. For example, Berge et al. describe pharmaceutically acceptable salts in detail in J. Pharmaceutical Sciences, 1977, 66, 1–19, incorporated herein by reference. Pharmaceutically acceptable salts of the compounds of this invention include those derived from suitable inorganic and organic acids and bases. Examples of pharmaceutically acceptable, nontoxic acid addition salts are salts of an amino group formed with inorganic acids, such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, and perchloric acid or with organic acids, such as acetic acid, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, or malonic acid or by using other methods known in the art such as ion exchange. Other pharmaceutically acceptable salts include adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, hydroiodide, 2–hydroxy– ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2–naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3–phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, valerate salts, and the like. Salts derived from appropriate bases include alkali metal, alkaline earth metal, ammonium, and N ⁺ (C _1–4 alkyl) ₄ - salts. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like. Further pharmaceutically acceptable salts include, when appropriate, nontoxic ammonium, quaternary ammonium, and amine cations formed using counterions such as halide, hydroxide, carboxylate, sulfate, phosphate, nitrate, lower alkyl sulfonate, and aryl sulfonate. The term “solvate” refers to forms of the compound, or a salt thereof, that are associated with a solvent, usually by a solvolysis reaction. This physical association may include hydrogen bonding. Conventional solvents include water, methanol, ethanol, acetic acid, DMSO, THF, diethyl ether, and the like. The compounds described herein may be prepared, e.g., in crystalline form, and may be solvated. Suitable solvates include pharmaceutically acceptable solvates and further include both stoichiometric solvates and non-stoichiometric solvates. In certain instances, the solvate will be capable of isolation for example when one or more solvent molecules are incorporated in the crystal lattice of a crystalline solid. “Solvate” encompasses both solution- phase and isolatable solvates. Representative solvates include hydrates, ethanolates, and methanolates. The term “hydrate” refers to a compound that is associated with water. Typically, the number of the water molecules contained in a hydrate of a compound is in a definite ratio to the number of the compound molecules in the hydrate. Therefore, a hydrate of a compound may be represented, for example, by the general formula R⋅x H ₂ O, wherein R is the compound, and x is a number greater than 0. A given compound may form more than one type of hydrate, including, e.g., monohydrates (x is 1), lower hydrates (x is a number greater than 0 and smaller than 1, e.g., hemihydrates (R⋅0.5 H2O)), and polyhydrates (x is a number greater than 1, e.g., dihydrates (R⋅2 H2O) and hexahydrates (R⋅6 H2O)). The term “tautomers” or “tautomeric” refers to two or more interconvertible compounds resulting from at least one formal migration of a hydrogen atom and at least one change in valency (e.g., a single bond to a double bond, a triple bond to a single bond, or vice versa). The exact ratio of the tautomers depends on several factors, including temperature, solvent, and pH. Tautomerizations (i.e., the reaction providing a tautomeric pair) may catalyzed by acid or base. Exemplary tautomerizations include keto-to-enol, amide-to-imide, lactam-to-lactim, enamine-to- imine, and enamine-to-(a different enamine) tautomerizations. Compounds that have the same molecular formula but differ in the nature or sequence of bonding of their atoms or the arrangement of their atoms in space are termed “isomers.” Isomers that differ in the arrangement of their atoms in space are termed “stereoisomers.” Stereoisomers that are not mirror images of one another are termed “diastereomers,” and those that are non-superimposable mirror images of each other are termed “enantiomers.” When a compound has an asymmetric center, for example, it is bonded to four different groups, a pair of enantiomers is possible. An enantiomer can be characterized by the absolute configuration of its asymmetric center and is described by the R- and S-sequencing rules of Cahn and Prelog, or by the manner in which the molecule rotates the plane of polarized light and designated as dextrorotatory or levorotatory (i.e., as (+) or (-)-isomers respectively). A chiral compound can exist as either individual enantiomer or as a mixture thereof. A mixture containing equal proportions of the enantiomers is called a “racemic mixture.” The term “prodrug” refers to a compound that becomes active, e.g., by solvolysis, reduction, oxidation, or under physiological conditions, to provide a pharmaceutically active compound, e.g., in vivo. A prodrug can include a derivative of a pharmaceutically active compound, such as, for example, to form an ester by reaction of the acid, or acid anhydride, or mixed anhydrides moieties of the prodrug moiety with the hydroxyl moiety of the pharmaceutical active compound. See, Bundgard, H., Design of Prodrugs, pp.7-9, 21-24, Elsevier, Amsterdam 1985. “Click chemistry” reaction includes Huisgen alkyne-azide cycloaddition. Any “click chemistry” reaction known in the art can be used to this end. Click chemistry is a chemical approach introduced by Sharpless in 2001 and describes chemistry tailored to generate substances quickly and reliably by joining small units together. See, e.g., Kolb, Finn and Sharpless Angewandte Chemie International Edition (2001) 40: 2004–2021; Evans, Australian Journal of Chemistry (2007) 60: 384–395). Exemplary coupling reactions (some of which may be classified as “click chemistry”) include, but are not limited to, formation of esters, thioesters, amides (e.g., such as peptide coupling) from activated acids or acyl halides; nucleophilic displacement reactions (e.g., such as nucleophilic displacement of a halide or ring opening of strained ring systems); azide–alkyne Huisgen cycloaddition; thiol–yne addition; imine formation; Michael additions (e.g., maleimide addition); and Diels–Alder reactions (e.g., tetrazine [4 + 2] cycloaddition). The terms “composition” and “formulation” are used interchangeably. A “subject” to which administration is contemplated refers to a human (i.e., male or female of any age group, e.g., pediatric subject (e.g., infant, child, or adolescent) or adult subject (e.g., young adult, middle–aged adult, or senior adult)) or non–human animal. In certain embodiments, the non–human animal is a mammal (e.g., primate (e.g., cynomolgus monkey or rhesus monkey), commercially relevant mammal (e.g., cattle, pig, horse, sheep, goat, cat, or dog), or bird (e.g., commercially relevant bird, such as chicken, duck, goose, or turkey)). In certain embodiments, the non-human animal is a fish, reptile, or amphibian. The non-human animal may be a male or female at any stage of development. The non-human animal may be a transgenic animal or genetically engineered animal. The term “administer,” “administering,” or “administration” refers to implanting, absorbing, ingesting, injecting, inhaling, or otherwise introducing a compound described herein, or a composition thereof, in or on a subject. The terms “treatment,” “treat,” and “treating” refer to reversing, alleviating, delaying the onset of, or inhibiting the progress of a disease described herein. In some embodiments, treatment may be administered after one or more signs or symptoms of the disease have developed or have been observed. In other embodiments, treatment may be administered in the absence of signs or symptoms of the disease. For example, treatment may be administered to a susceptible subject prior to the onset of symptoms (e.g., in light of a history of symptoms and/or in light of exposure to a pathogen). Treatment may also be continued after symptoms have resolved, for example, to delay and/or prevent recurrence. The term “prevent,” “preventing,” or “prevention” refers to a prophylactic treatment of a subject who is not and was not with a disease but is at risk of developing the disease or who was with a disease, is not with the disease, but is at risk of regression of the disease. In certain embodiments, the subject is at a higher risk of developing the disease or at a higher risk of regression of the disease than an average healthy member of a population of subjects. The terms “condition,” “disease,” and “disorder” are used interchangeably. An “effective amount” of a compound described herein refers to an amount sufficient to elicit the desired biological response. An effective amount of a compound described herein may vary depending on such factors as the desired biological endpoint, the pharmacokinetics of the compound, the condition being treated, the mode of administration, and the age and health of the subject. In certain embodiments, an effective amount is a therapeutically effective amount. In certain embodiments, an effective amount is a prophylactically effective amount. In certain embodiments, an effective amount is the amount of a compound or pharmaceutical composition described herein in a single dose. In certain embodiments, an effective amount is the combined amounts of a compound or pharmaceutical composition described herein in multiple doses. A “therapeutically effective amount” of a compound described herein is an amount sufficient to provide a therapeutic benefit in the treatment of a condition or to delay or minimize one or more symptoms associated with the condition. A therapeutically effective amount of a compound means an amount of therapeutic agent, alone or in combination with other therapies, which provides a therapeutic benefit in the treatment of the condition. The term “therapeutically effective amount” can encompass an amount that improves overall therapy, reduces or avoids symptoms, signs, or causes of the condition, and/or enhances the therapeutic efficacy of another therapeutic agent. A “prophylactically effective amount” of a compound described herein is an amount sufficient to prevent a condition, or one or more symptoms associated with the condition or prevent its recurrence. A prophylactically effective amount of a compound means an amount of a therapeutic agent, alone or in combination with other agents, which provides a prophylactic benefit in the prevention of the condition. The term “prophylactically effective amount” can encompass an amount that improves overall prophylaxis or enhances the prophylactic efficacy of another prophylactic agent. The term “therapeutic agent” includes an agent that is capable of providing a local or systemic biological, physiological, or therapeutic effect in the biological system to which it is applied For example a therapeutic agent can act to control tumor growth control infection or inflammation, act as an analgesic, promote anti-cell attachment, and enhance bone growth, among other functions. Other suitable therapeutic agents can include anti-viral agents, hormones, antibodies, or therapeutic proteins. Other therapeutic agents include prodrugs, which are agents that are not biologically active when administered but, upon administration to a subject are converted to biologically active agents through metabolism or some other mechanism. Additional terms may be defined in other sections of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS The figures are exemplary and do not limit the scope of the present disclosure. FIG.1 shows GPC traces illustrating the successful polymerization of tetrazine- terminated brush polymers. BP: brush polymer. FIG.2 shows GPC traces illustrating the successful polymerization of tetrazine- terminated brush polymers. FIGs.3A to 3B show GPC traces illustrating the successful polymerization of drug loaded brush polymers. For Fig 3A, red color is MMAE-F; pink color is MMAE-S; blue color is DOX. For Fig.3B, gray color is PTX; black color is SN38; green color is MMAE-M. FIGs.4A to 4D show results of antibody lysine modification. FIG.4A shows a scheme of the antibody lysine modification. Mass spectra were obtained for IgG (FIG.4B), NHS (N- hydroxysuccinimide) small molecule with PEG12 (PEG12) (FIG.4C) and NHS small molecule with PEG8 (PEG8) (FIG.4D). “Ab” refers to antibody. FIG.5A shows a mass spectrum of an anti-HER2 brush polymer conjugate. FIG.5B are images of SDS-PAGE gels that showed successful anti-HER2 brush polymer conjugation due to the smear band in the higher molecular weight and disappearance of the free antibody band. “Ctrl” refers to control. FIGs.6A to 6B show anti-HER2 ABCs in the SKBR-3 cell line (HER2 high expression). Results show that ABCs can significantly enhance cell uptake toward HER2 high expression cell line. FIGs.7A to 7B show anti-HER2 ABCs in the SKOV-3 cell line (HER2 medium expression). Results show that ABCs can significantly enhance cell uptake toward HER2 medium expression cell line. FIGs.8A to 8B show anti-HER2 ABCs in the MCF-10A cell line (control cell line, no HER2 expression). Results show that ABCs cannot enhance cell uptake toward HER2 no expression cell line, demonstrating the specificity. FIGs.9A to 9B show anti-HER2 ABCs in HCC-1954 (HER2 medium expression) and BT-474 cell line (HER2 high expression). Results show that ABCs can also significantly enhance cell uptake toward the other HER2 expression cell lines. FIGs.10A to 10B show cell toxicity studies on drug conjugated ABCs. Results show that ABCs can induce significantly higher toxicity compared to brush polymers (Pol) toward the HER2 expression cell lines, while they exhibited similar toxicity toward the control cell line (MCF-10A). FIGs.11A to 11D show cell toxicity studies in the SKBR-3 cell line. Results show that ABCs can induce significantly higher toxicity compared to brush polymers (Pol) and free drugs toward HER2 expression cell lines. FIGs.12A to 12B show cell toxicity studies in the HCC-1954 cell line. Results show that ABCs can induce significantly higher toxicity compared to brush polymers (Pol) toward low HER2 expression cell lines. FIG.13 shows cell toxicity studies in the SKOV-3 cell line. Results show that ABCs can induce significantly higher toxicity compared to brush polymers (Pol) toward medium HER2 expression cell lines. FIG.14 shows cell toxicity studies in the MCF-10A (control) cell line. Results show that ABCs exhibited similar toxicity to brush polymers (Pol) toward the control cell line without HER2 expression. FIGs.15A to 15C show cell toxicity studies in SKBR-3 (FIG.15A), HCC-1954 (FIG. 15B) and BT-474 (FIG.15C) cell lines with the free antibody (Ab) as a control. Results show that the antibody itself has no toxicity toward these cell lines. The brush polymer (Pol) and the physical mixture of antibody and brush polymer (Pol+Ab) have similar toxicity, significantly lower than ABCs. FIGs.16A to 16D show anti-BCMA based ABCs for targeted delivery. FIG.16A shows a conjugation and delivery process (FG: functional group). FIG.16B shows efficient conjugation between TCO functionalized antibodies and Tz terminated bottle brush polymers based on SDS PAGE gel. FIG.16C shows enhanced cell uptake for the ABC comparing to the bottle brush polymer prodrug (BPD) by flow cytometry in MM.1S cell line. FIG.16D shows enhanced cell uptake for ABC comparing to BPD by flow cytometry in KMS cell line. FIGs.17A to 17E show schemes of four strategies for antibody-polymer conjugation prepared thorough click reactions between the antibody and polymer. FIG.17A: an azide-DBCO conjugation. FIGs.17B to 17C: a Tz-TCO conjugation. FIGs.17B and 17D: another azide- DBCO conjugation. FIG.17E: another Tz-TCO conjugation. Tz: tetrazine. TCO: trans- cyclooctene. G3: the third generation Grubbs catalyst. . FIGs.18A to 18E show an antibody-polymer conjugation using the strategy shown in FIG.17A. *P4: control polymer; IgG1: 1:5 linker reaction (1 mg scale, 1mL); IgG2: 1:10 linker reaction (1 mg scale, 1 mL); IgG3: 1:15 linker reaction (1 mg scale, 1 mL). “DP” refers to degree of polymerization. FIG.18A shows conjugation efficiency between DBCO functionalized IgG antibody and azide functionalized bottle brush polymer with different DPs at different ratios. FIG.18B shows conjugation efficiency between DBCO functionalized IgG antibody and azide functionalized bottle brush polymer with different DPs at a ratio of 1:2. FIG.18C shows GPC traces of the bottle brush polymers with different DPs. FIG.18D shows comparison of GPC traces for the bottle brush polymers with DP=30 and macromonomer. FIG.18E shows SDS PAGE gel data from azide terminated bottle brush polymers with short linker. FIGs.19A to 19B show an antibody-polymer conjugation using the strategy shown in FIGs.17B to 17C. FIG.19A shows GPC traces of NHS functional group terminated bottle brush polymers: green color is macromonomer; blue color is bottle brush polymer with DP=60; blue color is dye labelled bottle brush polymer with DP=60. FIG.19B shows GPC traces of terminal functional group transformation for NHS terminated bottle brush polymers. FIGs.20A to 20D show antibody-polymer conjugations using the strategy shown in FIGs. 17B and 17D (IgG-DBCO + Pol-azide) or the strategy shown in FIGs.17B and 17C (IgG-Tz + Pol-TCO). FIG.20A shows SDS PAGE gel for efficiency of conjugation between antibody and bottle brush polymer. The conjugation is much more efficient based on Tz-TCO reaction than DBCO-azide reaction. FIG.20B shows SDS PAGE gel for conjugation between TCO functionalized IgG antibody and Tz functionalized bottle brush polymer. IgG + Pol-TCO and IgG-Tz + Pol-Ctrl were controls. FIG.20C shows SDS PAGE gel for conjugation kinetics between TCO functionalized IgG antibody and Tz functionalized bottle brush polymer. The reaction was efficient, which was finished in 14h. FIG.20D shows SDS PAGE gel for conjugation between TCO functionalized antibodies (IgG2a and anti-BCMA) and Tz functionalized bottle brush polymer. FIGs.21A to 21C show SDS PAGE gels for different fractions of the conjugates after FPLC separation. FIGs.22A to 22C show synthesis of dye labeled polymers for conjugation. FIG.22A shows SDS PAGE gel for conjugation between different dye labelled polymers and antibodies. FIG.22B shows MALDI-TOF mass spectrometry of IgG antibody. FIG.22C shows MALDI- TOF mass spectrometry of different amounts of TCO functional group modified IgG antibody. FIGs.23A to 23E show ROMP for drug conjugated MMs (macromonomers). FIG.23A shows GPC trace of DOX loaded bottle brush polymer with NHS functional terminal group. FIG. 23B shows GPC trace of SN38 loaded bottle brush polymer with NHS functional terminal group. FIG.23C shows GPC traces of DOX loaded bottle brush polymer with different DPs (10 and 60). FIG.23D shows GPC traces of SN38 loaded bottle brush polymer with different DPs (10, 30, and 60). FIG.23E shows GPC traces of PTX loaded bottle brush polymer with different DPs (10 and 60). There polymers are homopolymerized and the results showed unreacted monomers. FIGs. 24A to 24I show block or statistic polymerization for ROMP of drug conjugated MMs using an antibody-polymer conjugation using the strategy shown in FIGs.17B and 17C. FIG. 24A and FIG. 24B show SDS PAGE gel of conjugates between drug loaded polymers with different DPs and IgG antibody from a post modification strategy in FIG. 17C. FIG. 24C shows GPC traces of polymers from copolymerization of PEG based MMs and PTX loaded MMs at 1:1 ratio with statistic or blocky strategies. FIG. 24D shows GPC traces of polymers from copolymerization of PEG based MMs and PTX loaded MMs at 1:3 ratio with statistic or blocky strategies. FIG.24E shows GPC traces of polymers from homopolymerization of PTX loaded MM. FIG.24F, FIG.24G, and FIG.24H show GPC traces of homopolymerization of PEG based MM. FIG.24I shows SDS PAGE gel of conjugates between drug loaded polymers with different DPs and IgG antibody using strategy in FIG.17E. FIG.25A shows anti-HER-2 ABCs using the strategy shown in FIGs.17B and 17C after FPLC purification. FIG.25B shows anti-HER-2 and IgG ABCs using the strategy shown in FIG. 17E before and after FPLC purification. FIG.26 shows the structures of MMAE-S-MM, MMAE-M-MM, and MMAE-F-MM. FIG.27 shows the structures of drug conjugated MMs. FIG.28 shows cell uptake of BPD, ctrl-ABC (ctrl ABC, Ctrl-ABC, Ctrl ABC, CtrlABC, control ABC, non-binding ABC, or NB-ABC), and ABCs from flow cytometry. The anti-HER2 antibody was used for targeting moiety for ABCs and BT474 cell line was chosen with high surface HER2 expression.2 represents the BPD treatment; 3 represents ctrl-ABC treatment; 4 represents ABC treatment. The ABC treatment group showed much higher cell uptake comparing to BPD and ctrl-ABC treatment groups, meaning the higher targeting efficiency of the ABC treatment group. FIG.29 shows DLS measurements of brush polymer (“Polymer”), antibody (“Trastuzumab”), antibody-TCO (“Trastuzumab-TCO”), and ABCs (“Trastuzumab ABC”). The size of the Trastuzumab is 9 nm After TCO surface modification the size is increased to 10 nm for Trastuzumab-TCO. The size of brush polymer with DP60 is 15 nm. The size of the ABCs is 25 nm, which is significant bigger than Trastuzumab-TCO and BPD. These results suggested the successful conjugation between antibody and brush polymer. FIG.30 shows confocal images for cell uptake. There was almost no cell uptake after 4 h incubation for BPD and ctrl ABC as their high PEGylation. In contrast, the ABCs showed very high cell uptake. There were a lot of signals from the cell membrane and also significant amount of the signal from the intracellular environment, suggesting efficient cell binding between ABCs and cells with subsequent cell uptake. FIG.31A shows PK of BPD, ctrl-ABC and ABC. The pharmacokinetics of the ABCs, BPD and control ABCs were measured to access the circulation half-life of these materials. In order to monitor these materials in vivo, the brush polymer was labeled by a higher amount of Cy5.5 fluorescent dye. The ABC, BPD and control ABC treatment groups contained the same amount of dye according to the same amount of polymer was injected into mice. The time dependent blood samples were collected and analyzed. ABC, BPD and control ABC showed similar PK. FIG.31B shows blood remaining content after circulation for 72 h. More than 40% of polymers for ABC, BPD and Ctrl ABC was left inside the blood after 72 h. The dye labelled trastuzumab was also studied for the comparison of the PK. We tested the fluorescence of the Ab after 72 h injection and there is almost no signal for dye labelled Ab after 72 h. FIG.31C shows ex vivo images of different organs after 72 h. The BT474 tumor bearing mice was i.v. injected by BPD, ctrl ABC and ABC with PBS as a control. At first, we harvested the organ and the time dependent ex vivo images were taken. After 12 h, ABC showed similar distribution in different tissues with BPD and control ABCs, where the majority of the ABCs was accumulated inside the liver. With the increase of the time to 36 h, ABCs were solely accumulated in tumor significantly without the other tissues. However, there is no accumulation in tumor for BPD and Ctrl ABC. Further, the accumulation in tumor for ABCs was further increased at 72 h. These results highlight the targeting efficiency of the ABCs over BPD and Ctrl ABCs. FIG.31D shows biodistribution after 72 h. Time dependent biodistribution was evaluated. The other control groups were used to determination the targeting efficiency of the ABCs. The polymer itself without antibody conjugation (“BPD”) and a control ABC with the targeting ability were also used for biodistribution study. The ABC was accumulated inside the BT474 tumor with time. FIG.31E shows tumor signal comparison after 72 h. We compared the BT474 tumor fluorescence signals with different treatment groups. ABC treatment groups showed significantly higher signal comparing to BPD and ctrl ABC treatment groups. FIG.31F shows biodistribution of dye labelled antibody after 72 h. We monitored the biodistribution of the ADC mimic, where the Ab were labelled by Cy5.5 dye directly. There is slight accumulation inside the BT474 tumor. However, significant amount of ADC mimics was accumulated in liver at 72 h. These results are consistent with the fact that less than 1% of ADCs accumulates in tumor tissue. FIG.32A shows tumor volume after treatment of PBS (Control), BPD, ctrl ABC and ABC with MMAE as the payload. We used the anti-HER2 antibody as the targeting moiety and the BT474 xenograft tumor model was used to evaluate the in vivo performance of MMAE loaded ABCs (with anti-HER2 MMAE). The antitumor efficacy was monitored thorough the measurement of tumor volume size. We dosed the mice with 1.7 mg/kg MMAE in the format of BPD, Ctrl ABC (with IgG1 MMAE), and ABC (with anti-HER2 MMAE) once the tumors reach an average size of ~50-100 mm ³ with the frequency of once a week and total 4 doses. The tumor sizes of the control group were continuous increasing during the study. The ABC treatment group significantly decreased the tumor size even after the first dose. There is no tumor after 40 days with four doses of ABCs treatment. BPD and Ctrl ABC also showed anti-cancer effects after 4 doses treatment, but the antitumor efficacy was not achieved after the initial 3 doses, which was worse than the ABCs. Due to the high potency of MMAE, the non-targeted BPD and Ctrl-ABC reached good therapeutic efficacy after 4 doses treatment. FIG.32B shows body weight measurements for different treatment groups with MMAE as the payload. There is no toxicity after the injections as demonstrated by no significant body weight decrease. All the treatment groups showed almost the same body weight evolution as the control group. FIG.32C shows BT474 tumor weight measurements for different treatment groups with MMAE as the payload. The mice were sacrificed, and the tumor was harvested after the treatments. Tumor weight was measured after 40 days. The results showed the superior anticancer activities of the ABC treatment, which is consistent with the tumor volume measurement. FIG.32D shows BT474 tumor volume after treatment of PBS, BPD, ctrl ABC, or ABC with SN38 as the payload. Our results showed the continuous decrease of the tumor size after injection of the ABC, while the control group without treatment showed significant increase of the tumor size. For the BPD and Ctrl ABC groups, the tumor size was still increasing but much slower than the control group After 7 doses of injection the tumor totally disappeared for the ABC treatment even when the drug administration was stopped. The tumors for BPD and ctrl group continued to grow once the drug administration was stopped. FIG.32E shows body weight measurements for different treatment groups with SN38 as the payload. The injected drugs didn’t show any toxicity for the treatment groups as there was no significant weight loss for all the treatment groups. FIG.32F shows survival curves for different treatment groups with SN38 as the payload. The survival study was also performed for these different treatment groups. All the mice for control group were dead after 70 days with a half-life of ~30 days. The BPD and Ctrl ABC still had some anti-cancer efficiency. During this period of study, there were 1 in 6 mice survived for BPD and 2 in 6 mice survived for ctrl ABC treatment groups. For the ABC treatment group, all the mice survived without tumor after 280 days period study. These results highlight the superior anticancer efficacy of the ABC strategy with SN38 drug. FIG.32G shows BT474 tumor volume after treatment of PBS, BPD, ctrl ABC, or ABC with DOX as the payload. With the promising results from MMAE and SN38 for the ABC strategy, we then applied the ABC strategy to an less potent drug, DOX, for in vivo anticancer study, where DOX was previously failed for the ADCs development due to its low potency. As the ABC strategy can achieve very high DAR and high PK with long circulation time, we hypothesize that our ABC platform is applicable to DOX to reveal anticancer efficiency. To test that, we also used the BT474 xenograft mouse model to study the anticancer efficiency of ABCs with anti-HER2 DOX. Different prodrug platforms such as ABCs, BPD, and a control ABC with a nontargeting antibody were used for anti-cancer study. The ABCs showed superior anticancer efficacy after 4 doses treatment as the significant decrease of the tumor size over time. There was totally no tumor after the treatment till 40 days. However, the BPD and Ctrl ABC showed no therapeutic effects after 4 doses comparing to the control group. FIG.32H shows body weight measurements for different treatment groups with DOX as the payload. The injected drugs didn’t show any toxicity for the treatment groups as there is no significant weight loss for all the treatment groups. FIG.32I shows BT474 tumor weight measurements for different treatment groups with DOX as the payload. The tumor was harvested after 40 days study. The tumor size showed significant difference between the ABC treatment group and the other groups. There was almost no tumor for the ABC treatment group with superior anticancer efficacy, while there was no difference between the BPD, ctrl ABC treatment groups, and the control group without any treatment. Further, the tumor weight correlated well with the tumor size and volume measurement. FIG.33A shows comparison of BT474 tumor volume measurements after different treatments with one dose injection. We performed the antitumor efficacy study to compare the ABC platform to the benchmark commercially available Kadcyla (T-DM1, “ADC”) targeting HER2+ tumors. In this study, different groups of materials (Control, ABC_Blank, 3 ABCs (ABC_MMAE, ABC_SN38, ABC_DOX), ADC) were injected to mice to evaluate their efficacy. In this case, we used the ABC platform with different payloads for study. We also further pursued a one-dose therapy. All the ADC and the ABCs showed good anticancer efficiency as comparing to the control group, and ABC_Blank, which was without any payload. ABCs with high potency MMAE payload and medium potency SN38 payload performed better anti-tumor effect than the ADC treatment. Even the low potency DOX loaded ABC showed better efficacy. FIG.33B shows body weight measurements for different treatment groups. There was no toxicity after the injections as demonstrated by no significant body weight decrease. All the treatment groups showed almost the same body weight evolution as the control group. FIG.33C shows tumor comparison of BT474 tumor volume measurements after 40 days. ABCs with high potency MMAE payload and medium potency SN38 payload performed better anti-tumor effect than the ADC treatment. Even the low potency DOX loaded ABC showed better efficacy. FIG.33D shows BT474 tumor picture for different treatment groups. After 40 days, the mice were sacrificed, and the tumors were harvested. The results show that all ABCs with different payloads no matter the potency exhibited good anticancer efficacy similar to or better than Kadcyla (“ADC”). FIG.33E shows BT474 tumor weight measurements for different treatment groups. After 40 days, the mice were sacrificed and the tumors were harvested. The results shown that all ABCs with different payloads no matter the potency exhibited good anticancer efficacy similar to or better than Kadcyla (“ADC”). FIG.34A shows tumor volume after treatment of PROTAC based ABCs and control groups. We used the ABC platform for antibody targeted delivery of PROTAC to tumors for cancer therapy. We chose ARV771 as the payload. We used PROTAC-ABC (ABC_ARV771) to perform in vivo anti-cancer study. The HER2 overexpressed BT474 xenograft mice model was also used for this study.6 different treatments were performed on mice bearing ~50 mm ³ volume tumor.3 doses for treatment were performed once a week. BPD_ARV771, CtrlABC_ARV771, free ARV771, and free ARV825 showed little therapeutic effects, and the tumors continuously grew with almost the same trend as the control group. In contrast, PROTAC-ABC showed very good anticancer efficacy, and the tumor was almost disappeared after 3-doses treatment. FIG.34B shows body weight measurements after treatment of PROTAC-ABC (ABC_ARV771) and control groups. There was no toxicity after the injections as demonstrated by no significant body weight decrease. All the treatment groups showed almost the same body weight evolution as the control group. FIG.34C shows BT474 tumor volume measurements after treatment of PROTAC-ABC (ABC_ARV771) and control groups at day 30. BPD_ARV771, CtrlABC_ARV771, free ARV771, and free ARV825 showed no therapeutic effects, as the tumor sizes were almost the same as the control group. In contrast, PROTAC-ABC showed very good anticancer efficacy, and the tumor was almost disappeared after 3-doses treatment. FIG.34D shows BT474 tumor picture for different treatment groups with a PROTAC (ARV771) as payload. After 1-month study, the mice were sacrificed, and the tumor was collected. Except ABC treatment group, all the other groups showed similar tumor size comparing to the control group. The ABC treatment group showed excellent antitumor efficacy as almost totally disappearance of the tumor. ABC: ABC_ARV771. BPD: BPD_ARV771. Ctrl ABC: CtrlABC_ARV771. FIG.34E shows BT474 tumor weight measurements after treatment of PROTAC-ABC (ABC_ARV771) and control groups. Except ABC treatment group, all the other groups showed very similar tumor weight comparing to the control group. The ABC treatment group showed excellent antitumor efficacy as almost totally disappearance of the tumor. Comparing to the literature results, the doses for our study is much lower with much less dosing frequency (once a week vs daily). Importantly, our targeted delivery platform can show superior anticancer efficacy. FIG.35A shows ex vivo images of different organs with MUC1 model. MUC1 is an important surface expressed antigen for cancer therapy and has been ranked as the 2nd most promising antigen among 75 candidates by NCI. MUC1 is aberrantly overexpressed in different types of cancers such as ovarian cancer, lung cancer and breast cancer etc. CAOV3 cell line is an ovarian cancer cell line with high expression of MUC1 antigen on the surface. We also made the anti-MUC1 ABC using the same strategy as the anti-HER2 based ABCs. We performed in vivo study with a CAOV3 xenograft cancer model. Before anti-cancer study, we also evaluated the in vivo biodistribution study with ABC, BPD, and ctrl-ABC groups by ex vivo image. The ABC was efficiently accumulated inside the tumor tissue. FIG.35B shows CAOV3 tumor volume after treatment of PBS, BPD, ctrl ABC, or ABC with MMAE as the payload and anti-MUC1 as the targeting antibody. The anticancer study was performed by the anti-MUC1 ABCs with MMAE as the payload. BPD and Ctrl ABC showed very similar anti-cancer efficacy comparing to the control group. ABC efficiently shrank the tumor volume, and there was totally out of tumor after four doses of injections. FIG.35C shows body weight measurements after treatment of PBS, BPD, ctrl ABC, or ABC with MMAE as the payload and anti-MUC1 as the targeting antibody. There is no toxicity after the injections as demonstrated by no significant body weight decrease. All the treatment groups showed almost the same body weight evolution as the control group. FIG.35D shows CAOV3 tumor volume at day 60 after treatment of PBS, BPD, ctrl ABC, or ABC with MMAE as the payload and anti-MUC1 as the targeting antibody. ABC showed outstanding anti-tumor efficacy comparing to the other treatment groups. FIG. 35E shows CAOV3 tumor picture for different treatment groups with MMAE as the payload and anti-MUC1 as the targeting antibody. We harvested the tumors after 60 days study. Overall, ABC showed outstanding anti-tumor efficacy. FIG.35F shows CAOV3 tumor weight measurements after treatments with MMAE as the payload and anti-MUC1 as the targeting antibody. We harvested the tumors after 60 days study. The tumor weights were measured. Overall, ABC showed outstanding anti-tumor efficacy. Together, our strategy highlights the modularity of different drugs and also different antibodies for targeted cancer therapy. FIG.36 shows cell uptake with different reaction ratios (feed ratios) between antibody and brush polymer. We studied the targeting efficiency of these conjugates with different polymer chains on each antibody. We did two experiments to explore the targeting efficiency. At first, we incubated the cells with the same amount of fluorophore for targeting evaluation. The cell uptake is similar when the chains on each antibody between 1-3 (e.g., n1 being 1, 2, or 3) with feed ratio less than 3:1 brush polymer : antibody. Further, when the chain number was increased to 4 (e.g., n1 being 4), the targeting efficiency was decreased. Secondly, we fed the same amount of antibody for cell uptake. The more conjugation chain will result in more payloads in each ABC. The highest targeting efficiency was the ABCs with average of 3 chains on each of the Ab (e.g., n1 being 3). Similarly, when the feed ratio was increased to 4:1 brush polymer : antibody (e.g., n1 being 4), the cell uptake was decreased. FIG.37 shows SDS PAGE gels with different feed ratios between antibodies and brush polymers. The conjugation process was controlled by different feed ratio between Ab-TCO and BP-Tz to achieve different brush polymers on each antibody. We changed the reaction ratio between the BP-Tz and Ab-TCO from 1:1 to 4:1. The reaction was monitored by SDS-PAGE gel. With the increase of the feed ratio of the brush polymer, the conjugation amount of the BP chain on each of the conjugates can be increased. This process was monitored by SDS-PAGE gel Two different antibodies (IgG2a and anti HER2) were used for the conjugation When 1 eq. of brush polymer was mixed with Ab-TCO, most of the antibody were consumed to form the conjugates with 1 brush polymer on each of the antibody. There were also some conjugates with more than one brush polymer on each antibody. Free antibody wasn’t totally consumed in the reaction. When the ratio between the brush polymer and antibody was further increased to 2, the main product was conjugates with 2 brush polymers on each antibody, with small amount of one brush polymer on one antibody and small amount of more than 3 brush polymers on each antibody. But there is no free antibody left. Further increase of the eq. of the brush polymer resulted in more brush polymers conjugated on one antibody on average. This reaction was more homogeneous than the traditional conjugation between antibody and small molecules, which typically results in ~40% of free antibody with an average DAR value of ~4. FIG.38 shows the separation of ABCs with one brush polymer on one antibody and two brush polymers on one antibody. After the conjugation, we purified these conjugates by FPLC through a cationic exchange column. In this process, we easily purified the conjugates with different brush polymer:antibody ratios. In the gel, we clear showed that ABCs with one brush polymerper antibody (aHER2_BP1), two brush polymers per antibody (aHER2_BP2), and three brush polymers per antibody (aHER2_BP3) were separated. DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE DISCLOSURE Enynes, End-Functionalized Polymers, Conjugates, and Methods of Preparation In one aspect, the present disclosure provides an enyne of Formula (I): (I), or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, wherein: X ¹ is S, O, Se, or a single bond; R ^11a is substituted or unsubstituted, C1-18 alkyl; each of R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ is independently H, halogen, substituted or unsubstituted, C _1-6 alkyl, –O–(substituted or unsubstituted, C _1-6 alkyl), substituted or unsubstituted carbocyclyl, or substituted or unsubstituted aryl; R ¹⁶ is H or substituted or unsubstituted, C1-6 alkyl; R ¹⁸ is H or substituted or unsubstituted, C _1-6 alkyl; each instance of R ¹⁷ is independently H or substituted or unsubstituted, C _1-6 alkyl; or R ¹⁶ and one instance of R ¹⁷ are joined with their intervening atoms to form substituted or unsubstituted carbocyclyl or substituted or unsubstituted heterocyclyl; and provided that –X ¹ –R ^11a is not –S–n-C ₁₂ H ₂₅ . In certain embodiments, the present disclosure provides the enyne of Formula (I), or a tautomer, isotopically labeled compound, or salt thereof (e.g., a tautomer or salt thereof). In certain embodiments, R ^11a is substituted or unsubstituted, C _1-6 alkyl. In certain embodiments, R ^11a is unsubstituted C1-6 alkyl. In certain embodiments, R ^11a is unsubstituted n-C3- 6 alkyl, e.g., n-C4H9. In certain embodiments, R ^11a is substituted or unsubstituted, C7-9 alkyl. In certain embodiments, R ^11a is substituted or unsubstituted, C _10-11 alkyl. In certain embodiments, R ^11a is substituted or unsubstituted, C ₁₂ alkyl. In certain embodiments, R ^11a is unsubstituted n- dodecyl. In certain embodiments, R ^11a is not unsubstituted n-dodecyl. In certain embodiments, R ^11a is substituted or unsubstituted, C13-15 alkyl. In certain embodiments, R ^11a is substituted or unsubstituted, C _16-18 alkyl. In certain embodiments, R ^11a is unsubstituted C _1-18 alkyl. In certain embodiments, R ^11a is unsubstituted C1-11 alkyl. In certain embodiments, R ^11a is unsubstituted n- C7-16 alkyl. In certain embodiments, the optional substituents included in R ^11a are independently halogen (e.g., F), –O–(unsubstituted C _1-6 alkyl), or –O–(C _1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, the present disclosure provides an enyne of Formula (I-1): (I-1), or a salt thereof, wherein: X ¹ is S; R ^11a is unsubstituted C1-18 alkyl; each of R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ are H; R ¹⁶ is H or unsubstituted C1 alkyl; R ¹⁸ is H or unsubstituted C ₁ alkyl; each instance of R ¹⁷ is independently H or unsubstituted C ₁ alkyl; provided that –X ¹ –R ^11a is not –S–n-C12H25. In certain embodiments, R ^11a is unsubstituted C _1-11 alkyl. In certain embodiments, R ^11a is unsubstituted C1-9 alkyl. In certain embodiments, R ^11a is unsubstituted C13-18 alkyl. In certain embodiments, R ^11a is unsubstituted C14-18 alkyl. In certain embodiments, Formula (I) is: , , . In another aspect, the present disclosure provides an enyne of Formula (II): (II), or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, wherein: X ¹ is S, O, Se, or a single bond; R ¹¹ is substituted or unsubstituted, C1-18 alkyl; each of R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ is independently H, halogen, substituted or unsubstituted, C1-6 alkyl, –O–(substituted or unsubstituted, C1-6 alkyl), substituted or unsubstituted carbocyclyl, or substituted or unsubstituted aryl; R ¹⁶ is H or substituted or unsubstituted, C _1-6 alkyl; R ¹⁸ is H or substituted or unsubstituted, C _1-6 alkyl; each instance of R ¹⁷ is independently H or substituted or unsubstituted, C1-6 alkyl; or R ¹⁶ and one instance of R ¹⁷ are joined with their intervening atoms to form substituted or unsubstituted carbocyclyl or substituted or unsubstituted heterocyclyl; single bond; L ³ is substituted or unsubstituted, C1-1000 alkylene, substituted or unsubstituted, C2-1000 alkenylene, substituted or unsubstituted, C _2-1000 alkynylene, substituted or unsubstituted, C _1-1000 heteroalkylene, substituted or unsubstituted, C _2-1000 heteroalkenylene, substituted or unsubstituted, C2-1000 heteroalkynylene, or a single bond; optionally wherein one or more backbone carbon atoms of the C1-1000 alkylene, C2- 1 ₀₀₀ alkenylene, C _2-1000 alkynylene, C _1-1000 heteroalkylene, C _2-1000 heteroalkenylene, or C _2- 1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits; at least one of L ² and L ³ is not a single bond; E ¹ is a thiophile, a first click-chemistry handle, a nucleophile, an electrophile, or a leaving group, H, halogen, substituted or unsubstituted, C _1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, –C(=O)R ^a , –C(=O)OR ^a , – C(=O)N(R ^a ) ₂ , –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a ) ₂ , –NO ₂ , –N ₃ , –NR ^a C(=O)R ^a , – NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a )2, –NR ^a C(=NR ^a )R ^a , –NR ^a C(=NR ^a )OR ^a , –NR ^a C(=NR ^a )N(R ^a )2, –OC(=O)R ^a , –OC(=O)OR ^a , –OC(=O)N(R ^a )2, –OC(=NR ^a )R ^a , –OC(=NR ^a )OR ^a , – OC(=NR ^a )N(R ^a ) ₂ , –NR ^a S(=O) ₂ R ^a , –NR ^a S(=O) ₂ OR ^a , –NR ^a S(=O) ₂ N(R ^a ) ₂ , –OS(=O)R ^a , – OS(=O)OR ^a , –OS(=O)N(R ^a )2, –S(=O)R ^a , –S(=O)OR ^a , –S(=O)N(R ^a )2, –OS(=O)2R ^a , – OS(=O)2OR ^a , –OS(=O)2N(R ^a )2, –S(=O)2R ^a , –S(=O)2OR ^a , –S(=O)2N(R ^a )2, or –P(=O)(R ^a )2; and each instance of R ^a is independently H, substituted or unsubstituted, C _1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, a nitrogen protecting group when attached to a nitrogen atom, an oxygen protecting group when attached to an oxygen atom, or a sulfur protecting group when attached to a sulfur atom, or two instances of R ^a attached to a nitrogen atom are joined with the nitrogen atom to form substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl. In certain embodiments, X ¹ is S. In certain embodiments, X ¹ is O. In certain embodiments X ¹ is a single bond In certain embodiments, R ¹¹ is substituted or unsubstituted, C1-6 alkyl. In certain embodiments, R ¹¹ is unsubstituted C1-6 alkyl. In certain embodiments, R ¹¹ is unsubstituted n-C3-6 alkyl, e.g., n-C ₄ H ₉ . In certain embodiments, R ¹¹ is substituted or unsubstituted, C _7-9 alkyl. In certain embodiments, R ¹¹ is substituted or unsubstituted, C10-11 alkyl. In certain embodiments, R ¹¹ is substituted or unsubstituted, C12 alkyl. In certain embodiments, R ¹¹ is unsubstituted n-dodecyl. In certain embodiments, R ¹¹ is not unsubstituted n-dodecyl. In certain embodiments, R ¹¹ is substituted or unsubstituted, C13-15 alkyl. In certain embodiments, R ¹¹ is substituted or unsubstituted, C16-18 alkyl. In certain embodiments, R ¹¹ is unsubstituted C1-18 alkyl. In certain embodiments, R ¹¹ is unsubstituted C _1-11 alkyl. In certain embodiments, R ¹¹ is unsubstituted n-C _{7- 16} alkyl. In certain embodiments, the optional substituents included in R ¹¹ are independently halogen (e.g., F), –O–(unsubstituted C1-6 alkyl), or –O–(C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, R ¹² is H. In certain embodiments, R ¹² is halogen (e.g., F, Cl). In certain embodiments, R ¹² is unsubstituted C1-6 alkyl (e.g., –CH3, –C2H5). In certain embodiments, R ¹² is substituted C1-6 alkyl (e.g., C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, R ¹² is –CF ₃ . In certain embodiments, R ¹² is –O–(unsubstituted C _1-6 alkyl) (e.g., –OCH3, –OC2H5). In certain embodiments, R ¹² is unsubstituted carbocyclyl (e.g., unsubstituted cyclopropyl). In certain embodiments, R ¹² is unsubstituted aryl (e.g., unsubstituted phenyl). In certain embodiments, R ¹² is aryl (e.g., phenyl) substituted with one or more halogen, unsubstituted C _1-6 alkyl, C _1-6 alkyl substituted with one or more halogen, or –O–(unsubstituted C1-6 alkyl). In certain embodiments, R ¹³ is H. In certain embodiments, R ¹³ is halogen (e.g., F, Cl). In certain embodiments, R ¹³ is unsubstituted C _1-6 alkyl (e.g., –CH ₃ , –C ₂ H ₅ ). In certain embodiments, R ¹³ is substituted C1-6 alkyl (e.g., C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, R ¹³ is –CF3. In certain embodiments, R ¹³ is –O–(unsubstituted C1-6 alkyl) (e.g., –OCH ₃ , –OC ₂ H ₅ ). In certain embodiments, R ¹³ is unsubstituted carbocyclyl (e.g., unsubstituted cyclopropyl). In certain embodiments, R ¹³ is unsubstituted aryl (e.g., unsubstituted phenyl). In certain embodiments, R ¹³ is aryl (e.g., phenyl) substituted with one or more halogen, unsubstituted C _1-6 alkyl, C _1-6 alkyl substituted with one or more halogen, or –O–(unsubstituted C _1-6 alkyl). In certain embodiments, R ¹⁴ is H. In certain embodiments, R ¹⁴ is halogen (e.g., F, Cl). In certain embodiments, R ¹⁴ is unsubstituted C1-6 alkyl (e.g., –CH3, –C2H5). In certain embodiments, R ¹⁴ is substituted C _1-6 alkyl (e.g., C _1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments R ¹⁴ is CF3 In certain embodiments R ¹⁴ is O (unsubstituted C16 alkyl) (e.g., –OCH ₃ , –OC ₂ H ₅ ). In certain embodiments, R ¹⁴ is unsubstituted carbocyclyl (e.g., unsubstituted cyclopropyl). In certain embodiments, R ¹⁴ is unsubstituted aryl (e.g., unsubstituted phenyl). In certain embodiments, R ¹⁴ is aryl (e.g., phenyl) substituted with one or more halogen, unsubstituted C _1-6 alkyl, C _1-6 alkyl substituted with one or more halogen, or –O–(unsubstituted C1-6 alkyl). In certain embodiments, R ¹⁵ is H. In certain embodiments, R ¹⁵ is halogen (e.g., F, Cl). In certain embodiments, R ¹⁵ is unsubstituted C _1-6 alkyl (e.g., –CH ₃ , –C ₂ H ₅ ). In certain embodiments, R ¹⁵ is substituted C1-6 alkyl (e.g., C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, R ¹⁵ is –CF3. In certain embodiments, R ¹⁵ is –O–(unsubstituted C1-6 alkyl) (e.g., –OCH ₃ , –OC ₂ H ₅ ). In certain embodiments, R ¹⁵ is unsubstituted carbocyclyl (e.g., unsubstituted cyclopropyl). In certain embodiments, R ¹⁵ is unsubstituted aryl (e.g., unsubstituted phenyl). In certain embodiments, R ¹⁵ is aryl (e.g., phenyl) substituted with one or more halogen, unsubstituted C1-6 alkyl, C1-6 alkyl substituted with one or more halogen, or –O–(unsubstituted C _1-6 alkyl). In certain embodiments, each of R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ is independently H, halogen, unsubstituted C1-3 alkyl, or –O–(unsubstituted C1-3 alkyl). In certain embodiments, each of R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ is H. In certain embodiments, R ¹⁶ is H. In certain embodiments, R ¹⁶ is unsubstituted C _1-6 alkyl, e.g., –C2H5. In certain embodiments, R ¹⁶ is unsubstituted C1-3 alkyl, e.g., –CH3. In certain embodiments, R ¹⁶ is substituted C1-6 alkyl (e.g., C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, R ¹⁶ is –CF ₃ . In certain embodiments, R ¹⁸ is H. In certain embodiments, R ¹⁸ is unsubstituted C _1-6 alkyl, e.g., –C2H5. In certain embodiments, R ¹⁸ is unsubstituted C1-3 alkyl, e.g., –CH3. In certain embodiments, R ¹⁸ is substituted C1-6 alkyl (e.g., C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, R ¹⁸ is –CF ₃ . In certain embodiments, each instance of R ¹⁷ is H. In certain embodiments, R ¹⁷ is one instance of R ¹⁷ is H, and the other instance of unsubstituted C1-6 alkyl, e.g., –C2H5. In certain embodiments, one instance of R ¹⁷ is H, and the other instance of R ¹⁷ is unsubstituted C _1-3 alkyl, e.g., –CH3. In certain embodiments, one instance of R ¹⁷ is H, and the other instance of R ¹⁷ is substituted C1-6 alkyl (e.g., C1-6 alkyl substituted with one or more halogen (e.g., F)). In certain embodiments, one instance of R ¹⁷ is H, and the other instance of R ¹⁷ is –CF ₃ . In certain embodiments, each instance of R ¹⁷ is independently unsubstituted C _1-3 alkyl, e.g., –CH ₃ . In certain embodiments, the carbon atom to which two R ¹⁷ are attached is of the R configuration. In certain embodiments, the carbon atom to which two R ¹⁷ are attached is of the S configuration. In certain embodiments, R ¹⁶ and one instance of R ¹⁷ are joined with their intervening atoms to form substituted or unsubstituted carbocyclyl eg unsubstituted cyclopropyl In certain embodiments, L ² is –C(=O)–, –S(=O) ₂ –, or –S(=O)–. In certain embodiments, L ² is –C(=O)–. In certain embodiments, L ² is a single bond. In certain embodiments, L ³ is substituted or unsubstituted, C1-30 alkylene. In certain embodiments, L ³ is substituted or unsubstituted, C _30-100 alkylene. In certain embodiments, L ³ is substituted or unsubstituted, C100-300 alkylene. In certain embodiments, L ³ is substituted or unsubstituted, C300-1000 alkylene. In certain embodiments, L ³ is substituted or unsubstituted, C _1-30 heteroalkylene. In certain embodiments, L ³ is substituted or unsubstituted, C30-100 heteroalkylene. In certain embodiments, L ³ is substituted or unsubstituted, C100-300 heteroalkylene. In certain embodiments, L ³ is substituted or unsubstituted, C _300-1000 heteroalkylene. In certain embodiments, optionally wherein one, two, three, four, or five backbone carbon atoms of the C1-1000 alkylene, C2-1000 alkenylene, C2-1000 alkynylene, C1-1000 heteroalkylene, C2-1000 heteroalkenylene, or C2-1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C1-30 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _1-30 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C _30-100 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C30-100 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C100-300 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _100-300 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C _300-1000 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C300-1000 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene as valency permits In certain embodiments, L ³ is substituted or unsubstituted, C _1-30 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C1-30 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C30-100 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _30-100 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C _100-300 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C100-300 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C300-1000 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _300-1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C _1-1000 alkylene or substituted or unsubstituted, C1-1000 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C1-1000 alkylene or C1-1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, L ³ is substituted or unsubstituted, C3-400 alkylene or substituted or unsubstituted, C _2-400 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C3-400 alkylene or C2-400 heteroalkylene are independently replaced with substituted or unsubstituted, monocyclic, 3- to 10-membered carbocyclylene, substituted or unsubstituted, monocyclic, 3- to 10-membered heterocyclylene, substituted or unsubstituted phenyl, or substituted or unsubstituted, monocyclic, 5- to 6-membered heteroarylene, as valency permits. In certain embodiments, the optional substituents included in L ³ are independently halogen (e.g., F), unsubstituted C1-6 alkyl, C1-6 alkyl substituted with one or more halogen (e.g., F), –O–(unsubstituted C _1-6 alkyl), –O–(C _1-6 alkyl substituted with one or more halogen (e.g., F)), or oxo In certain embodiments, the carbocyclylene or heterocyclylene included in L ³ is monocyclic and 3- to 10-membered. In certain embodiments, the arylene included in L ³ is phenylene. In certain embodiments, the heteroarylene included in L ³ is monocyclic and 5- to 6- membered. In certain embodiments, L ³ is unsubstituted C1-10 alkylene, unsubstituted para-phenylene, , wherein: each instance of q is independently an integer from 1 to 10, inclusive; each instance of r1 is independently an integer from 2 to 40, inclusive; each instance of s is independently 0 or 1; each instance of t is independently an integer from 0 to 10, inclusive; each instance of r2 is independently an integer from 0 to 10, inclusive; each instance of r3 is independently an integer from 0 to 40, inclusive; each instance of r4 is independently 0 or 1; each instance of r5 is independently an integer from 0 to 10, inclusive; and the attachment point marked with “ ” is attached to L ² . In certain embodiments, Formula (II) is: ,

,

In another aspect, the present disclosure provides an end-functionalized polymer of Formula (III): (III) or a tautomer, isotopically labeled polymer, or salt thereof, wherein: B ¹ is a polymer, wherein the polymer comprises one or more pharmaceutical agents; L ¹ is substituted or unsubstituted, C1-1000 alkylene, substituted or unsubstituted, C2-1000 alkenylene, substituted or unsubstituted, C _2-1000 alkynylene, substituted or unsubstituted, C _1-1000 heteroalkylene, substituted or unsubstituted, C2-1000 heteroalkenylene, or substituted or unsubstituted, C2-1000 heteroalkynylene; optionally wherein one or more backbone carbon atoms of the C _1-1000 alkylene, C _2- 1000 alkenylene, C2-1000 alkynylene, C1-1000 heteroalkylene, C2-1000 heteroalkenylene, or C2- 1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits; E ¹ is a thiophile, a first click-chemistry handle, a nucleophile, an electrophile, or a leaving group, H, halogen, substituted or unsubstituted, C1-6 alkyl, substituted or unsubstituted, C2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, –C(=O)R ^a , –C(=O)OR ^a , – C(=O)N(R ^a ) ₂ , –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a ) ₂ , –NO ₂ , –N ₃ , –NR ^a C(=O)R ^a , – NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a )2, –NR ^a C(=NR ^a )R ^a , –NR ^a C(=NR ^a )OR ^a , –NR ^a C(=NR ^a )N(R ^a )2, –OC(=O)R ^a , –OC(=O)OR ^a , –OC(=O)N(R ^a )2, –OC(=NR ^a )R ^a , –OC(=NR ^a )OR ^a , – OC(=NR ^a )N(R ^a ) ₂ , –NR ^a S(=O) ₂ R ^a , –NR ^a S(=O) ₂ OR ^a , –NR ^a S(=O) ₂ N(R ^a ) ₂ , –OS(=O)R ^a , – OS(=O)OR ^a , –OS(=O)N(R ^a ) ₂ , –S(=O)R ^a , –S(=O)OR ^a , –S(=O)N(R ^a ) ₂ , –OS(=O) ₂ R ^a , – OS(=O)2OR ^a , –OS(=O)2N(R ^a )2, –S(=O)2R ^a , –S(=O)2OR ^a , –S(=O)2N(R ^a )2, or –P(=O)(R ^a )2; and each instance of R ^a is independently H, substituted or unsubstituted, C1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, a nitrogen protecting group when attached to a nitrogen atom, an oxygen protecting group when attached to an oxygen atom, or a sulfur protecting group when attached to a sulfur atom, or two instances of R ^a attached to a nitrogen atom are joined with the nitrogen atom to form substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl. In certain embodiments, B ¹ is a brush polymer or star polymer. In certain embodiments, B ¹ is a brush polymer. In certain embodiments, B ¹ is a condensation polymer. In certain embodiments, B ¹ is a polyamide, polyester, polyacetal, polycarbonate, polyurethane, polyepoxide, or polysiloxane. In certain embodiments, B ¹ is an addition polymer. In certain embodiments B ¹ is a polyethylene polypropylene polystyrene polyvinyl chloride polytetrafluoroethylene, polyvinylidene dichloride, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyisoprene, polybutadiene, or polychloroprene. In certain embodiments, the number average molecular weight of B ¹ as determined by gel permeation chromatography is between 1,000 and 3,000, between 3,000 and 10,000, between 10,000 and 30,000, between 30,000 and 100,000, between 100,000 and 300,000, or between 300,000 and 1,000,000, g/mol, inclusive. In certain embodiments, the number average degree of polymerization of B ¹ as determined by gel permeation chromatography is between 2 and 4, between 4 and 6, or between 7 and 9, inclusive. In certain embodiments, the number average degree of polymerization of B ¹ as determined by gel permeation chromatography is between 10 and 20, between 20 and 40, between 40 and 60, between 60 and 80, between 80 and 100, between 100 and 300, or between 300 and 1,000, inclusive. In certain embodiments, the dispersity of B ¹ is between 1.0 and 1.2, between 1.2 and 1.5, between 1.5 and 2.0, between 2.0 and 2.5, or between 2.5 and 3.0, inclusive. In certain embodiments, the crosslinking degree of B ¹ is between 0% and 1%, inclusive. In certain embodiments, the crosslinking degree of B ¹ is between 1% and 10%, between 10% and 20%, between 20% and 30%, between 30% and 40%, between 40% and 50%, or between 50% and 60%, inclusive. In certain embodiments, B ¹ is prepared by a method comprising polymerizing one or more types of monomers in the presence of a metathesis catalyst. In certain embodiments, B ¹ is prepared by a method comprising polymerizing one or more types of monomers through ring- opening metathesis polymerization. In certain embodiments, B ¹ is prepared by a method comprising polymerizing one or more types of monomers through radical polymerization, cationic polymerization, or anionic polymerization. In certain embodiments, B ¹ is prepared by a method comprising polymerizing one or more types of monomers of Formula (A), or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, in the presence of a metathesis catalyst. In certain embodiments, at least one type of the monomers is a macromonomer. In certain embodiments, the end-functionalized polymer, or a tautomer, isotopically labeled polymer, or salt thereof, is prepared by a method comprising: (a) metathesis polymerizing one or more types of monomers in the presence of a metathesis catalyst to form a living polymer of Formula (B): (B), wherein each instance of the monomers comprises one or more non-aromatic alkenyl and/or one or more alkynyl; and (b) reacting the living polymer with an enyne, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof. In another aspect, the present disclosure provides a method of preparing an end- functionalized polymer of Formula (III), or a tautomer, isotopically labeled polymer, or salt thereof, the method comprising reacting a living polymer of Formula (B): (B); with the enyne, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co- crystal thereof. In certain embodiments, the method further comprises metathesis polymerizing one or more types of monomers in the presence of a metathesis catalyst to form the living polymer, wherein each instance of the monomers comprises one or more non-aromatic alkenyl and/or one or more alkynyl. In certain embodiments, the step of metathesis polymerizing comprises ring-opening metathesis polymerization (ROMP) (see, e.g., Liu et al. J. Am. Chem. Soc. 2012, 134, 16337; Liu, J.; Gao, A. X.; Johnson, J. A. J Vis Exp 2013, e50874). In certain embodiments, the metathesis catalyst is a ROMP catalyst. ROMP catalysts useful in the synthetic methods described herein include catalysts as depicted below, and as described in Grubbs et al., Acc. Chem. Res. 1995, 28, 446–452; U.S. Pat. No. 5,811,515; Schrock et al., Organometallics (1982) 11645; Gallivan et al., Tetrahedron Letters (2005) 46:2577–2580; Furstner et al., J. Am. Chem. Soc. (1999) 121:9453; and Chem. Eur. J. (2001) 7:5299; the entire contents of each of which are incorporated herein by reference. In certain embodiments, the metathesis catalyst is a transition metal metathesis catalyst. In certain embodiments, the metathesis catalyst is a tungsten (W), molybdenum (Mo), or ruthenium (Ru) catalyst. In certain embodiments, the metathesis catalyst is a Grubbs catalyst. In certain embodiments, the metathesis catalyst is of the formula: . In certain embodiments, the Grubbs catalyst is: X = Cl; Br; I Cy = cyclohexyl benzylidenebis–(tricyclohexylphosphine)–dichlororutheniu m (X = Cl); benzylidenebis–(tricyclohexylphosphine)–dibromoruthenium (X = Br); benzylidenebis–(tricyclohexylphosphine)–diiodoruthenium (X = I); X = Cl; Br; I R = cyclohexyl (Cy); phenyl (Ph); benzyl (Bn) 1,3–(bis(mesityl)–2–imidazolidinylidene)dichloro–(ph enylmethylene) (tricyclohexyl– phosphine)ruthenium (X = Cl; R = cyclohexyl); 1,3–(bis(mesityl)–2–imidazolidinylidene)dibromo–(phe nylmethylene) (tricyclohexyl– phosphine)ruthenium (X = Br; R = cyclohexyl); 1,3–(bis(mesityl)–2–imidazolidinylidene)diiodo–(phen ylmethylene) (tricyclohexyl– phosphine)ruthenium (X = I; R = cyclohexyl); 1,3–(bis(mesityl)–2–imidazolidinylidene)dichloro–(ph enylmethylene) (triphenylphosphine)ruthenium (X = Cl; R = phenyl); 1,3–(bis(mesityl)–2–imidazolidinylidene)dichloro–(ph enylmethylene) (tribenzylphosphine)ruthenium (X = Cl; R = benzyl); ,

. In certain embodiments, the metathesis catalyst is a Grubbs-Hoveyda catalyst. In certain embodiments, the Grubbs-Hoveyda catalyst is of the formula: . In certain embodiments, the metathesis catalyst is of the formula: Or (Furstner catalyst). In certain embodiments, the metathesis catalyst is of the formula: In certain embodiments, the molar ratio of the metathesis catalyst to the monomers is between 1:10 and 1:30, between 1:30 and 1:100, between 1:100 and 1:300, between 1:300 and 1:1,000, inclusive. In certain embodiments, the molar ratio of the metathesis catalyst to the monomers is between 1:20 and 1:200, inclusive. The step of metathesis polymerizing can be conducted in one or more aprotic solvents. The term “aprotic solvent” means a non-nucleophilic solvent having a boiling point range above ambient temperature, preferably from about 25 ºC to about 190 ºC at atmospheric pressure. In certain embodiments, the aprotic solvent has a boiling point from about 80 ºC to about 160 ºC at atmospheric pressure. In certain embodiments, the aprotic solvent has a boiling point from about 80 ºC to about 150 ºC at atmospheric pressure. Examples of such solvents are methylene chloride, acetonitrile, toluene, DMF, diglyme, THF, and DMSO. Step (b) may be performed according to the methods described in Fu et al., J. Am. Chem. Soc., 2018, 140, 12181−12188; and/or Zhang et al., Macromolecules, 2018, 51, 6497−6503, each of which is incorporated by reference in its entirety. In certain embodiments, at least one instance of the monomers is of Formula (A): (A), or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, wherein: each instance of R ^A is independently H, halogen, or substituted or unsubstituted, C _1-6 alkyl; each instance of a is independently an integer from 0 to 20, inclusive; each instance of R ¹ is independently H, halogen, or substituted or unsubstituted, C _1-6 alkyl, or two R ¹ attached to the same carbon atom are taken together to form oxo; each instance of R ² is independently H, halogen, or substituted or unsubstituted, C1-6 alkyl, or two R ² attached to the same carbon atom are taken together to form oxo; each instance of L is substituted or unsubstituted, C _1-1000 alkylene, substituted or unsubstituted, C2-1000 alkenylene, substituted or unsubstituted, C2-1000 alkynylene, substituted or unsubstituted, C _1-1000 heteroalkylene, substituted or unsubstituted, C _2-1000 heteroalkenylene, or substituted or unsubstituted, C _2-1000 heteroalkynylene; optionally wherein one or more backbone carbon atoms of the C1-1000 alkylene, C2- 1000 alkenylene, C2-1000 alkynylene, C1-1000 heteroalkylene, C2-1000 heteroalkenylene, or C2- 1 ₀₀₀ heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits; each instance of M is independently a pharmaceutical agent; each instance of m is independently an integer from 1 to 10, inclusive; each instance of R ^B is independently H, halogen, or substituted or unsubstituted, C1-6 alkyl; each instance of b is independently an integer from 0 to 20, inclusive; each instance of e is independently an integer from 1 to 10, inclusive; each instance of X is –OR ^C or –N(R ^D )2; each instance of R ^C is independently H, substituted or unsubstituted, C _1-1000 alkyl, substituted or unsubstituted, C2-1000 alkenyl, substituted or unsubstituted, C2-1000 alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C _2-1000 heteroalkynyl, an oxygen protecting group, or a leaving group; and each instance of R ^D is independently H, substituted or unsubstituted, C1-1000 alkyl, substituted or unsubstituted, C _2-1000 alkenyl, substituted or unsubstituted, C _2-1000 alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C2-1000 heteroalkynyl, or a nitrogen protecting group, or two R ^D attached to the same nitrogen atom are taken together with the nitrogen atom to form substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl. In certain embodiments, B ¹ is of Formula (B-1): or a salt thereof, wherein: each instance of R ^A is independently hydrogen, halogen, or substituted or unsubstituted, C1-6 alkyl; a is an integer from 1 to 20, inclusive; each instance of –Y–Z– is independently each instance of M ¹ is independently hydrogen or a pharmaceutical agent; each instance of m is independently an integer from 1 to 10, inclusive; each instance of L is independently substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted C _{2 200} alkenylene substituted or unsubstituted C _{2 200} alkynylene substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, or C2-200 heteroalkynylene, wherein: optionally one or more carbons in each instance of the substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C _2-200 alkenylene, substituted or unsubstituted, C _2-200 alkynylene, substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; and optionally one or more heteroatoms in each instance of the substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, and substituted or unsubstituted, C _2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; provided that when each instance of M ¹ is hydrogen, at least one instance of –L(M ¹ ) _m comprises a click-chemistry handle; each instance of W is independently a single bond, –O–, –S–, or –NR ^E –; each instance of R ^E is independently hydrogen, substituted or unsubstituted C _1-6 alkyl, or a nitrogen protecting group; each instance of W′ is independently –O–, –S–, or –NR ^J –; each instance of R ^J is independently hydrogen, substituted or unsubstituted C1-6 alkyl, or a nitrogen protecting group; each instance of R ^K and R ^L is independently hydrogen, halogen, substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-6 alkenyl, substituted or unsubstituted C2-6 alkynyl, substituted or unsubstituted, 3- to 7-membered, monocyclic carbocyclyl, substituted or unsubstituted, 3- to 7-membered, monocyclic heterocyclyl, substituted or unsubstituted phenyl, substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , – CN, –SCN, –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a )2, –C(=O)R ^a , –C(=O)OR ^a , – C(=O)N(R ^a ) ₂ , –NO ₂ , –NR ^a C(=O)R ^a , –NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a ) ₂ , –OC(=O)R ^a , – OC(=O)OR ^a , or –OC(=O)N(R ^a ) ₂ ; each instance of R ^a is independently hydrogen, substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C _2-6 alkenyl, substituted or unsubstituted C _2-6 alkynyl, substituted or unsubstituted, 3- to 7-membered, monocyclic carbocyclyl, substituted or unsubstituted, 3- to 7- membered, monocyclic heterocyclyl, substituted or unsubstituted phenyl, substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl, an oxygen protecting group when attached to an oxygen atom a sulfur protecting group when attached to a sulfur atom or a nitrogen protecting group when attached to a nitrogen atom; or two instances of R ^a attached to the same nitrogen atom are joined to form substituted or unsubstituted, 3- to 7-membered, monocyclic heterocyclyl, or substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl; each instance of T is independently a single bond, substituted or unsubstituted, C1-20 alkylene, substituted or unsubstituted, C2-20 alkenylene, substituted or unsubstituted, C2-20 alkynylene, substituted or unsubstituted, C _2-20 heteroalkylene, substituted or unsubstituted, C _2-20 heteroalkenylene, or C2-20 heteroalkynylene, wherein: optionally one or more carbons in each instance of the substituted or unsubstituted, C1-20 alkylene, substituted or unsubstituted, C _2-20 alkenylene, substituted or unsubstituted, C _2-20 alkynylene, substituted or unsubstituted, C _2-20 heteroalkylene, substituted or unsubstituted, C _2-20 heteroalkenylene, and C2-20 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; and optionally one or more heteroatoms in each instance of the substituted or unsubstituted, C2-20 heteroalkylene, substituted or unsubstituted, C2-20 heteroalkenylene, and substituted or unsubstituted, C _2-20 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; each instance of R ^B is independently hydrogen, halogen, or substituted or unsubstituted, C _1-6 alkyl; each instance of b is independently an integer from 1 to 20, inclusive; e is an integer from 1 to 10, inclusive; and n2 is an integer from 5 to 300, inclusive; X is OR ^C or N(R ^D )2, wherein: R ^C is hydrogen, substituted or unsubstituted, C1-1000 alkyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ alkenyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ alkynyl, substituted or unsubstituted, C ₁ - ₁₀₀₀ heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C2- 1000 heteroalkynyl, an oxygen protecting group, or a leaving group; each instance of R ^D is independently hydrogen, substituted or unsubstituted, C ₁ - ₁₀₀₀ alkyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ alkenyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C2-1000 heteroalkynyl, or a nitrogen protecting group; and R ^P is hydrogen, substituted or unsubstituted C _1-6 alkyl, or substituted or unsubstituted phenyl. In certain embodiments, each instance of R ^A is independently hydrogen, halogen, or substituted or unsubstituted, C _1-6 alkyl; a is an integer from 1 to 20, inclusive; each instance of –Y–Z– is independently each instance of M ¹ is independently hydrogen or a pharmaceutical agent; each instance of m is independently an integer from 1 to 10, inclusive; each instance of L is independently substituted or unsubstituted, C _1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, or C _2-200 heteroalkynylene, wherein: optionally one or more carbons in each instance of the substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, and C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; and optionally one or more heteroatoms in each instance of the substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and substituted or unsubstituted, C _2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; provided that when each instance of M ¹ is hydrogen, at least one instance of –L(M ¹ ) _m comprises a click-chemistry handle; each instance of W is independently a single bond or –O–; each instance of R ^K and R ^L is independently hydrogen, halogen, substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-6 alkenyl, substituted or unsubstituted C2-6 alkynyl, substituted or unsubstituted, 3- to 7-membered, monocyclic carbocyclyl, substituted or unsubstituted, 3- to 7-membered, monocyclic heterocyclyl, substituted or unsubstituted phenyl, substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , – CN, –SCN, –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a )2, –C(=O)R ^a , –C(=O)OR ^a , – C(=O)N(R ^a ) ₂ , –NO ₂ , –NR ^a C(=O)R ^a , –NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a ) ₂ , –OC(=O)R ^a , – OC(=O)OR ^a , or –OC(=O)N(R ^a ) ₂ ; each instance of R ^a is independently hydrogen, substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-6 alkenyl, substituted or unsubstituted C2-6 alkynyl, substituted or unsubstituted, 3- to 7-membered, monocyclic carbocyclyl, substituted or unsubstituted, 3- to 7- membered, monocyclic heterocyclyl, substituted or unsubstituted phenyl, substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl, an oxygen protecting group when attached to an oxygen atom, a sulfur protecting group when attached to a sulfur atom, or a nitrogen protecting group when attached to a nitrogen atom; or two instances of R ^a attached to the same nitrogen atom are joined to form substituted or unsubstituted, 3- to 7-membered, monocyclic heterocyclyl, or substituted or unsubstituted, 5- or 6-membered, monocyclic heteroaryl; each instance of T is independently a single bond, substituted or unsubstituted, C1-20 alkylene, substituted or unsubstituted, C2-20 alkenylene, substituted or unsubstituted, C2-20 alkynylene, substituted or unsubstituted, C _2-20 heteroalkylene, substituted or unsubstituted, C _2-20 heteroalkenylene, or C2-20 heteroalkynylene, wherein: optionally one or more carbons in each instance of the substituted or unsubstituted, C1-20 alkylene, substituted or unsubstituted, C _2-20 alkenylene, substituted or unsubstituted, C _2-20 alkynylene, substituted or unsubstituted, C2-20 heteroalkylene, substituted or unsubstituted, C2-20 heteroalkenylene, and C2-20 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; and optionally one or more heteroatoms in each instance of the substituted or unsubstituted, C2-20 heteroalkylene, substituted or unsubstituted, C2-20 heteroalkenylene, and substituted or unsubstituted, C _2-20 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; each instance of R ^B is independently hydrogen, halogen, or substituted or unsubstituted, C _1-6 alkyl; each instance of b is independently an integer from 1 to 20, inclusive; e is an integer from 1 to 10, inclusive; and X is OR ^C or N(R ^D ) ₂ , wherein: R ^C is hydrogen, substituted or unsubstituted, C1-1000 alkyl, substituted or unsubstituted, C2-1000 alkenyl, substituted or unsubstituted, C2-1000 alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ heteroalkenyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ heteroalkynyl, an oxygen protecting group, or a leaving group; and each instance of R ^D is independently hydrogen, substituted or unsubstituted, C1-1000 alkyl, substituted or unsubstituted, C2-1000 alkenyl, substituted or unsubstituted, C2-1000 alkynyl, substituted or unsubstituted, C ₁ - ₁₀₀₀ heteroalkyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ heteroalkenyl, substituted or unsubstituted, C2-1000 heteroalkynyl, or a nitrogen protecting group. In certain embodiments, B ¹ is of Formula (B-1-a): , or a salt thereof. In certain embodiments, B ¹ is of Formula (B-1-b):

or a salt thereof. In certain embodiments, B ¹ is of Formula (B-1-c): or a salt thereof. In certain embodiments, B ¹ is of Formula (B-1-d): or a salt thereof. In certain embodiments, B ¹ is of Formula (B-1-e): or a salt thereof. In certain embodiments, B ¹ is of Formula (B-1-f): or a salt thereof. In certain embodiments, each instance of R ^A is hydrogen. In certain embodiments, a is an integer from 2 to 20, inclusive. In certain embodiments, at least one instance of L is substituted or unsubstituted, C2-200 alkynylene. In certain embodiments, at least one instance of L is substituted or unsubstituted, C _{2- 200} heteroalkynylene. In certain embodiments, at least one instance of L is substituted or unsubstituted, C2-200 heteroalkylene, wherein one or more carbons and/or one or more heteroatoms, of the substituted or unsubstituted, C2-200 heteroalkylene, are independently replaced with substituted or unsubstituted heteroarylene. In certain embodiments, at least one instance of L is substituted or unsubstituted, C _3-30 heteroalkylene, wherein one or two carbons and/or one or two heteroatoms, of the substituted or unsubstituted, C3-30 heteroalkylene are independently replaced with substituted or unsubstituted phenylene or substituted or unsubstituted, monocyclic, 5- or 6-membered heteroarylene. In certain embodiments, at least one instance of L is substituted or unsubstituted, C2-200 heteroalkylene, wherein one or more carbons and/or one or more heteroatoms, of the substituted or unsubstituted, C2-200 heteroalkylene, are independently replaced with , wherein the nitrogen atom labeled with “ ” is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, one carbon or one heteroatom, of the substituted or unsubstituted, C2-200 heteroalkylene, is replaced with , wherein the nitrogen atom labeled is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L comprises , wherein: each instance of p is independently an integer from 1 to 10, inclusive; each instance of L ^F is independently substituted or unsubstituted, C2-180 heteroalkylene; and the nitrogen atom labeled with “ ” is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L is . In certain embodiments, at least one instance of L ^F comprises –S–S–. In certain embodiments, at least one instance of L ^F comprises a peptide comprising between 1 and 20, inclusive, amino acid residues. In certain embodiments, at least one instance of L comprises , wherein: each instance of p is independently an integer from 1 to 10 inclusive; each instance of q is independently an integer from 1 to 10, inclusive; each instance of r is independently an integer from 0 to 10, inclusive; each instance of s is independently 0 or 1; each instance of t is independently an integer from 0 to 10, inclusive; and the nitrogen atom labeled with “*” is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L is . In certain embodiments, at least one instance of L is , wherein r is 1, 2, or 3; and t is 1 or 2. In certain embodiments, at least one instance of L comprises , wherein: each instance of p is independently an integer from 1 to 10, inclusive; each instance of L ^C is independently substituted or unsubstituted, C _1-180 alkylene; and the nitrogen atom labeled with “ ” is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L is . In certain embodiments, R ^P is hydrogen. In certain embodiments, R ^P is substituted or unsubstituted C1-6 alkyl. In certain embodiments, R ^P is substituted or unsubstituted phenyl. In certain embodiments, R ^P is unsubstituted phenyl. In certain embodiments, n2 is an integer from 5 to 100, inclusive. In certain embodiments, n2 is an integer from 5 to 60, inclusive. In certain embodiments, n2 is an integer from 5 to 40, inclusive. In certain embodiments, n2 is an integer from 5 to 20, inclusive. In certain embodiments, n2 is an integer from 5 to 10, inclusive. In certain embodiments, n2 is an integer from 10 to 60, inclusive. In certain embodiments, n2 is an integer from 10 to 40, inclusive. In certain embodiments, n2 is an integer from 10 to 20, inclusive. In certain embodiments, n2 is an integer from 20 to 60, inclusive. In certain embodiments, n2 is an integer from 20 to 40, inclusive. In certain embodiments, B ¹ is of Formula (B-2): or a salt thereof, wherein: each instance of R ^A is independently hydrogen, halogen, or substituted or unsubstituted, C1-6 alkyl; a is an integer from 1 to 20, inclusive; each instance of M ¹ is independently hydrogen or a pharmaceutical agent; each instance of m is independently an integer from 1 to 10, inclusive; each instance of L is independently substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C _2-200 alkenylene, substituted or unsubstituted, C _2-200 alkynylene, substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, or substituted or unsubstituted, C2-200 heteroalkynylene, wherein: optionally one or more carbons in each instance of the substituted or unsubstituted, C _1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C2-200 alkynylene, substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and substituted or unsubstituted, C _2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; optionally one or more heteroatoms in each instance of the substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and substituted or unsubstituted, C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; provided that when each instance of M ¹ is hydrogen, at least one instance of –L(M ¹ )m comprises a click-chemistry handle; each instance of R ^B is independently hydrogen, halogen, or substituted or unsubstituted, C1-6 alkyl; each instance of b is independently an integer from 1 to 20, inclusive; e is an integer from 1 to 10, inclusive; n2 is an integer from 5 to 300, inclusive; and X is OR ^C or N(R ^D )2, wherein: R ^C is hydrogen, substituted or unsubstituted, C ₁ - ₁₀₀₀ alkyl, substituted or unsubstituted, C2-1000 alkenyl, substituted or unsubstituted, C2-1000 alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C2- ₁₀₀₀ heteroalkynyl, an oxygen protecting group, or a leaving group; each instance of R ^D is independently hydrogen, substituted or unsubstituted, C ₁ - ₁₀₀₀ alkyl, substituted or unsubstituted, C2-1000 alkenyl, substituted or unsubstituted, C2-1000 alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ heteroalkynyl, or a nitrogen protecting group, or two R ^D are taken together to form a substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl moiety; and R ^P is hydrogen, substituted or unsubstituted C _1-6 alkyl, or substituted or unsubstituted phenyl. In certain embodiments, R ^P is hydrogen. In certain embodiments, R ^P is substituted or unsubstituted C _1-6 alkyl. In certain embodiments, R ^P is substituted or unsubstituted phenyl. In certain embodiments, R ^P is unsubstituted phenyl. In certain embodiments, n2 is an integer from 5 to 100, inclusive. In certain embodiments, n2 is an integer from 5 to 60, inclusive. In certain embodiments, n2 is an integer from 5 to 40, inclusive. In certain embodiments, n2 is an integer from 5 to 20, inclusive. In certain embodiments, n2 is an integer from 5 to 10, inclusive. In certain embodiments, n2 is an integer from 10 to 60, inclusive. In certain embodiments, n2 is an integer from 10 to 40, inclusive. In certain embodiments, n2 is an integer from 10 to 20, inclusive. In certain embodiments, n2 is an integer from 20 to 60, inclusive. In certain embodiments, n2 is an integer from 20 to 40, inclusive. In certain embodiments, B ¹ is of Formula (B-3): or a salt thereof, wherein: each instance of R ^A is independently hydrogen, halogen, or substituted or unsubstituted, C1-6 alkyl; a is an integer from 1 to 20, inclusive; each instance of M is independently a pharmaceutical agent; each instance of m′ is independently an integer from 2 to 10, inclusive; each instance of L is independently substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, or substituted or unsubstituted, C2-200 heteroalkynylene, wherein: optionally one or more carbons in each instance of the substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C _2-200 alkenylene, substituted or unsubstituted, C _2-200 alkynylene, substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and substituted or unsubstituted, C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; and optionally one or more heteroatoms in each instance of the substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, and substituted or unsubstituted, C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; each instance of R ^B is independently hydrogen, halogen, or substituted or unsubstituted, C1-6 alkyl; each instance of b is independently an integer from 1 to 20, inclusive; e is an integer from 1 to 10, inclusive; n2 is an integer from 5 to 300, inclusive; and X is OR ^C or N(R ^D ) ₂ , wherein: R ^C is hydrogen, substituted or unsubstituted, C1-1000 alkyl, substituted or unsubstituted, C2-1000 alkenyl, substituted or unsubstituted, C2-1000 alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ heteroalkenyl, substituted or unsubstituted, C ₂ - 1000 heteroalkynyl, an oxygen protecting group, or a leaving group; and each instance of R ^D is independently hydrogen, substituted or unsubstituted, C1-1000 alkyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ alkenyl, substituted or unsubstituted, C ₂ - ₁₀₀₀ alkynyl, substituted or unsubstituted, C1-1000 heteroalkyl, substituted or unsubstituted, C2-1000 heteroalkenyl, substituted or unsubstituted, C2-1000 heteroalkynyl, or a nitrogen protecting group, or two R ^D are taken together to form a substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl moiety; each instance of R ¹ is independently hydrogen, halogen, or substituted or unsubstituted, C1-6 alkyl, or each instance of and R ^P is hydrogen, substituted or unsubstituted C1-6 alkyl, or substituted or unsubstituted phenyl. In certain embodiments, R ^P is hydrogen. In certain embodiments, R ^P is substituted or unsubstituted C1-6 alkyl. In certain embodiments, R ^P is substituted or unsubstituted phenyl. In certain embodiments, R ^P is unsubstituted phenyl. In certain embodiments, n2 is an integer from 5 to 100, inclusive. In certain embodiments, n2 is an integer from 5 to 60, inclusive. In certain embodiments, n2 is an integer from 5 to 40, inclusive. In certain embodiments, n2 is an integer from 5 to 20, inclusive. In certain embodiments, n2 is an integer from 5 to 10, inclusive. In certain embodiments, n2 is an integer from 10 to 60, inclusive. In certain embodiments, n2 is an integer from 10 to 40, inclusive. In certain embodiments, n2 is an integer from 10 to 20, inclusive. In certain embodiments, n2 is an integer from 20 to 60, inclusive. In certain embodiments, n2 is an integer from 20 to 40, inclusive. In certain embodiments, B ¹ is of Formula (B-4):

L ^1b is a substituted or unsubstituted linker, wherein the backbone of L ^1b comprises two or more atoms; each instance of R ^1a is independently halogen, substituted or unsubstituted, C1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, –C(=NR ^a )R ^a , – C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a )2, –C(=O)R ^a , –C(=O)OR ^a , –C(=O)N(R ^a )2, –NO2, –NR ^a C(=O)R ^a , – NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a ) ₂ , –OC(=O)R ^a , –OC(=O)OR ^a , or –OC(=O)N(R ^a ) ₂ , or two instances of R ^1a are joined to form substituted or unsubstituted carbocyclyl or substituted or unsubstituted heterocyclyl; each instance of R ^a is independently hydrogen, halogen, substituted or unsubstituted, C _1-6 alkyl substituted or unsubstituted C26 alkenyl substituted or unsubstituted C26 alkynyl substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, a nitrogen protecting group when attached to a nitrogen atom, an oxygen protecting group when attached to an oxygen atom, or a sulfur protecting group when attached to a sulfur atom, or two instances of R ^a on a nitrogen atom are joined with the nitrogen atom to form substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl; R ^P is hydrogen, substituted or unsubstituted C _1-6 alkyl, or substituted or unsubstituted phenyl; each instance of L is independently a bond or a substituted or unsubstituted linker; each instance of M is independently a pharmaceutical agent; each instance of m is independently an integer between 1 and 10, inclusive; n2 is an integer from 5 to 300, inclusive; and d is an integer between 1 and 10, inclusive. In certain embodiments, L ^1b is of the formula: , , wherein: n3 is an integer between 0 and 12 inclusive; k is an integer between 1 and 12 inclusive; j is an integer between 10 and 200 inclusive; and L ^1a is independently substituted or unsubstituted, C _1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, or C _{2- 200} heteroalkynylene, wherein: optionally one or more backbone carbon atoms in each instance of the substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C _2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclene, substituted or unsubstituted heterocyclene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; optionally one or more backbone heteroatoms in each instance of the substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and substituted or unsubstituted, C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclene, substituted or unsubstituted heterocyclene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene. In certain embodiments, R ^P is hydrogen. In certain embodiments, R ^P is substituted or unsubstituted C _1-6 alkyl. In certain embodiments, R ^P is substituted or unsubstituted phenyl. In certain embodiments, R ^P is unsubstituted phenyl. In certain embodiments, n2 is an integer from 5 to 100, inclusive. In certain embodiments, n2 is an integer from 5 to 60, inclusive. In certain embodiments, n2 is an integer from 5 to 40, inclusive. In certain embodiments, n2 is an integer from 5 to 20, inclusive. In certain embodiments, n2 is an integer from 5 to 10, inclusive. In certain embodiments, n2 is an integer from 10 to 60, inclusive. In certain embodiments, n2 is an integer from 10 to 40, inclusive. In certain embodiments, n2 is an integer from 10 to 20, inclusive. In certain embodiments, n2 is an integer from 20 to 60, inclusive. In certain embodiments, n2 is an integer from 20 to 40, inclusive. In certain embodiments, B ¹ is of Formula (B-4-a): , or a salt thereof, wherein:

L ^1b is a substituted or unsubstituted linker, wherein the backbone of L ^1b comprises two or more atoms; each instance of R ^1a is independently halogen, substituted or unsubstituted, C1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, –C(=NR ^a )R ^a , – C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a ) ₂ , –C(=O)R ^a , –C(=O)OR ^a , –C(=O)N(R ^a ) ₂ , –NO ₂ , –NR ^a C(=O)R ^a , – NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a ) ₂ , –OC(=O)R ^a , –OC(=O)OR ^a , or –OC(=O)N(R ^a ) ₂ , or two instances of R ^1a are joined to form substituted or unsubstituted carbocyclyl or substituted or unsubstituted heterocyclyl; each instance of R ^a is independently hydrogen, halogen, substituted or unsubstituted, C _1-6 alkyl, substituted or unsubstituted, C2-6 alkenyl, substituted or unsubstituted, C2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, a nitrogen protecting group when attached to a nitrogen atom, an oxygen protecting group when attached to an oxygen atom, or a sulfur protecting group when attached to a sulfur atom, or two instances of R ^a on a nitrogen atom are joined with the nitrogen atom to form substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl; R ^P is hydrogen, substituted or unsubstituted C1-6 alkyl, or substituted or unsubstituted phenyl; each instance of L is independently a bond or a substituted or unsubstituted linker; each instance of M is independently a pharmaceutical agent; each instance of m is independently an integer between 1 and 10, inclusive; n2 is an integer from 5 to 300, inclusive; and d is an integer between 1 and 10, inclusive. In certain embodiments, L ^1b is of the formula: , wherein: n3 is an integer between 0 and 12 inclusive; k is an integer between 1 and 12 inclusive; j is an integer between 10 and 200 inclusive; and L ^1a is independently substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C _2-200 heteroalkenylene, or C _{2- 200} heteroalkynylene, wherein: optionally one or more backbone carbon atoms in each instance of the substituted or unsubstituted, C1-200 alkylene, substituted or unsubstituted, C2-200 alkenylene, substituted or unsubstituted, C _2-200 alkynylene, substituted or unsubstituted, C _2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and C2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclene, substituted or unsubstituted heterocyclene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene; optionally one or more backbone heteroatoms in each instance of the substituted or unsubstituted, C2-200 heteroalkylene, substituted or unsubstituted, C2-200 heteroalkenylene, and substituted or unsubstituted, C _2-200 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclene, substituted or unsubstituted heterocyclene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene. In certain embodiments, R ^P is hydrogen. In certain embodiments, R ^P is substituted or unsubstituted C _1-6 alkyl. In certain embodiments, R ^P is substituted or unsubstituted phenyl. In certain embodiments, R ^P is unsubstituted phenyl. In certain embodiments, n2 is an integer from 5 to 100, inclusive. In certain embodiments, n2 is an integer from 5 to 60, inclusive. In certain embodiments, n2 is an integer from 5 to 40, inclusive. In certain embodiments, n2 is an integer from 5 to 20, inclusive. In certain embodiments, n2 is an integer from 5 to 10, inclusive. In certain embodiments, n2 is an integer from 10 to 60, inclusive. In certain embodiments, n2 is an integer from 10 to 40, inclusive. In certain embodiments, n2 is an integer from 10 to 20, inclusive. In certain embodiments, n2 is an integer from 20 to 60, inclusive. In certain embodiments, n2 is an integer from 20 to 40, inclusive. In certain embodiments, at least one instance (e.g., each instance) of the monomers is a monomer or macromonomer described in U.S. Patent Application Publication No.2014- 0308234, 2017-0348431, 2018-0094099, 2020-0123297, 2019-0038751, 2020-0369685, 2021- 0220391, or 2021-0113701, or in International PCT Application Publication No.2019/200367, each of which is incorporated by reference in its entirety. In certain embodiments, each instance of R ^A is independently H, F, Cl, or –CH3. In certain embodiments, each instance of R ^A is H. In certain embodiments, each instance of a is independently 2, 3, 4, 5, 6, or 7. In certain embodiments, each instance of a is 2, 3, 4, 5, 6, or 7. In certain embodiments, each two R ¹ attached to the same carbon atom are taken together to form oxo. In certain embodiments, each R ¹ is H. In certain embodiments, each two R ² attached to the same carbon atom are taken together to form oxo. In certain embodiments, each R ² is H. In certain embodiments, each two R ¹ attached to the same carbon atom are taken together to form oxo; and each R ² is H. In certain embodiments, each R ¹ is H, and each two R ² attached to the same carbon atom are taken together to form oxo. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _1-30 alkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C30-100 alkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C100-300 alkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _300-1000 alkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C1-30 heteroalkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _30-100 heteroalkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C100-300 heteroalkylene. In certain embodiments, each instance of L is independently substituted or unsubstituted, C300-1000 heteroalkylene. In certain embodiments, optionally wherein one, two, three, four, or five backbone carbon atoms of the C _1-1000 alkylene, C _2-1000 alkenylene, C _2-1000 alkynylene, C _1-1000 heteroalkylene, C _2-1000 heteroalkenylene, or C2-1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C1-30 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C1-30 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _30-100 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _30-100 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C100-300 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C100-300 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _300-1000 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _300-1000 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C1-30 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C1-30 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _30-100 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _30-100 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C100-300 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C100- 300 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene as valency permits In certain embodiments, each instance of L is independently substituted or unsubstituted, C300-1000 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C300- 1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C _1-1000 alkylene or substituted or unsubstituted, C _1-1000 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C1-1000 alkylene or C1-1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, each instance of L is independently substituted or unsubstituted, C3-400 alkylene or substituted or unsubstituted, C2-400 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _3-400 alkylene or C _2-400 heteroalkylene are independently replaced with substituted or unsubstituted, monocyclic, 3- to 10-membered carbocyclylene, substituted or unsubstituted, monocyclic, 3- to 10-membered heterocyclylene, substituted or unsubstituted phenyl, or substituted or unsubstituted, monocyclic, 5- to 6-membered heteroarylene, as valency permits. In certain embodiments, the optional substituents included in each instance of L are independently halogen (e.g., F), unsubstituted C _1-6 alkyl, C _1-6 alkyl substituted with one or more halogen (e.g., F), –O–(unsubstituted C _1-6 alkyl), –O–(C _1-6 alkyl substituted with one or more halogen (e.g., F)), or oxo. In certain embodiments, each instance of L comprises at least one instance of –O–C(=O)– or –C(=O)–O–. In certain embodiments, the carbocyclylene or heterocyclylene included in each instance of L is independently monocyclic and 3- to 7-membered. In certain embodiments, the arylene included in each instance of L is phenylene. In certain embodiments, the heteroarylene included in each instance of L is independently monocyclic and 5- to 6-membered. In certain embodiments, at least one instance (e.g., each instance) of L is independently substituted or unsubstituted, C _2-400 heteroalkylene, wherein: one or two backbone carbon atoms of the C 2-400 heteroalkylene are replaced with , wherein the nitrogen atom labeled with is closer to the attachment point labeled with “**” than the attachment point labeled with “***”; and optionally wherein one or two backbone carbon atoms of the C 2-400 heteroalkylene is replaced with substituted or unsubstituted phenylene.

In certain embodiments, at least one instance of L is independently substituted or unsubstituted, C2-200 heteroalkylene, wherein one carbon or one heteroatom, of the substituted or unsubstituted, C2-200 heteroalkylene, is independently replaced with , wherein the nitrogen atom labeled with is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L comprises wherein: each instance of p is independently an integer from 1 to 10, inclusive; each instance of L ^F is independently substituted or unsubstituted, C2-180 heteroalkylene; and the nitrogen atom labeled with is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L is independently . In certain embodiments, at least one instance of L comprises wherein: each instance of p is independently an integer from 1 to 10, inclusive; each instance of q is independently an integer from 1 to 10, inclusive; each instance of r is independently an integer from 0 to 10, inclusive; each instance of s is independently 0 or 1 ; each instance of t is independently an integer from 0 to 10, inclusive; and the nitrogen atom labeled with “*” is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L ^F is independently substituted or unsubstituted, C3-30 heteroalkylene. In certain embodiments, at least one instance of L ^F comprises –S–S–. In certain embodiments, at least one instance of L ^F is independently substituted or unsubstituted, C _3-30 heteroalkylene comprising one –S–S– and no other heteroatoms in the backbone. In certain embodiments, at least one instance of L ^F comprises a peptide comprising between 1 and 20 (e.g., between 1 and 4), inclusive, amino acid residues. In certain embodiments, at least one instance of L is independently i independently 1 or 2. In certain embodiments, at least one instance of L comprises , wherein: each instance of p is independently an integer from 1 to 10, inclusive; each instance of L ^C is independently substituted or unsubstituted, C1-180 alkylene; and the nitrogen atom labeled with “*” is closer to the attachment point labeled with “**” than the attachment point labeled with “***”. In certain embodiments, at least one instance of L is independently . In certain embodiments, at least one instance of L ^C is independently substituted or unsubstituted C _1-12 alkylene. In certain embodiments, at least one instance of L ^C is independently unsubstituted C _1-12 alkylene. In certain embodiments, each instance of L ^C is independently C1-180 alkylene substituted with one or more instances of: substituted or unsubstituted phenyl and/or substituted or unsubstituted, C1-6 alkyl. In certain embodiments, at least one instance of L comprises a polymer. In certain embodiments, at least one instance of the polymer is independently substituted or unsubstituted polyethylene (e.g., unsubstituted polystyrene). In certain embodiments, the weight-average molecular weight of at least one instance of the polymer is independently between 300 and 10,000, between 300 and 3,000, between 300 and 1,000, between 1,000 and 10,000, between 1,000 and 3,000, or between 3,000 and 10,000, inclusive, g/mol. In certain embodiments, at least one instance of L comprises an amino acid or a peptide. In certain embodiments, at least one instance the peptide consists of between 3 and 60, between 3 and 30, between 3 and 10, between 10 and 60, between 10 and 30, or between 30 and 60, inclusive, amino acids. In certain embodiments, each instance of the amino acid is independently a natural amino acid. In certain embodiments, at least one instance of the amino acid is independently an unnatural amino acid. A cleavable linker is “cleaved” or “degraded” when one or more bonds of the cleavable linker are broken, e.g., resulting in release of an agent, e.g., from the Brush prodrug or particle. Linker cleavage or agent release need not be 100%, e.g., a cleavage or release of at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95% or higher, e.g., over a period of seconds, minutes, hours (e.g., 6 hours, 12 hours, or 24 hours), days (e.g., 2 days or 7 days), weeks, or months is encompassed by this term. In certain embodiments, at least 50% of all instances of the L that is cleavable is cleaved after about 10 minutes, about 1 hour, about 6 hours, about 12 hours, about 1 day, about 2 days, about 3 days, about 5 days, or about 7 days of the ultraviolet irradiation, hydrolysis, reduction, oxidation, or contact with the enzyme. In some embodiments, the cleavable linker is cleavable by or is sensitive to an enzyme (e.g., an esterase or a protease), pH (e.g., acidic pH, basic pH), light (e.g., ultraviolet light), a nucleophile, reduction, or oxidation. In some embodiments, the cleavable linker is cleavable by or is sensitive to an enzyme (e.g., an esterase or a protease) or pH (e.g., acidic pH, basic pH). In some embodiments, the cleavable linker is not cleavable by light (e.g., ultraviolet light). In certain embodiments, at least one instance of L is cleavable by ultraviolet irradiation. In certain embodiments, at least one instance of L is cleavable by hydrolysis, reduction, or oxidation. In certain embodiments, at least one instance of L is cleavable by contacting with an enzyme. The cleavable linker may include an atom or a part of a moiety that is derived in part from the agent (e.g., a therapeutic agent). In some embodiments, the cleavable linker is cleaved or degraded, e.g., preferentially cleaved or degraded, upon exposure to a first set of conditions relative to a second set of conditions. For example, the cleavable linker can be “preferentially cleaved” or “preferentially degraded” in a first set of conditions relative to a second set of conditions if at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95% or more of a bond or bonds of the cleavable linker are broken, or the agent is released, in the first set of conditions relative to the second set of conditions. In some embodiments, the cleavable linker is degraded or hydrolyzed at physiological conditions In some embodiments the linker is pH sensitive or cleaved at a certain pH In some embodiments, the linker is degraded or hydrolyzed through the action of an enzyme (e.g., a protease or esterase). For example, in some embodiments, the cleavable linker is preferentially cleaved in a tissue microenvironment, e.g., a tumor microenvironment, which is referred to herein as a “tissue microenvironment cleavable linker.” In embodiments, the tissue (e.g., tumor) microenvironment cleavable linker is preferentially cleaved or degraded upon exposure to a first desired tissue or tumor microenvironment relative to a second tissue or non-tumor tissue. A tissue (e.g., tumor) microenvironment cleavable linker can be preferentially cleaved if at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95% or more of a bond or bonds of the linker are broken, or the agent is released, in a desired tissue or tumor microenvironment relative to another tissue or non-tumor tissue. In one embodiment, the tissue (e.g., tumor) microenvironment cleavable linker is preferentially cleaved or degraded if one or more of the bonds of the linker are broken, or the agent is released, at least 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, or 100 times faster upon exposure to a first desired tissue or tumor microenvironment relative to a second tissue or non-tumor tissue. The tissue (e.g., tumor) microenvironment can have a particular set of conditions, e.g., pH, enzymes, that cause the cleavage or degradation of the linker. In certain embodiments, at least two instances of L are different from each other. In all instances of L are the same. In one embodiment, the tissue (e.g., tumor) microenvironment cleavable linker is cleavable by an enzyme. In some embodiments, the enzyme comprises an esterase or a protease. Exemplary proteases include MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, MMP-14, plasmin, PSA, PSMA, CATHEPSIN D, CATHEPSIN K, CATHEPSIN S, ADAM10, ADAM12, ADAMTS, Caspase-1, Caspase-2, Caspase-3, Caspase-4, Caspase-5, Caspase-6, Caspase-7, Caspase-8, Caspase-9, Caspase-10, Caspase-11, Caspase-12, Caspase-13, Caspase-14, or TACE. In other embodiments, the tissue microenvironment cleavable linker is cleavable at a particular pH. In some embodiments, the tissue microenvironment cleavable linker is cleavable at a pH between about 5.0 and about 7.4, between 5.0 and 7.0, between 5.0 and 6.5, between 5.0 and 5.5, or between 5.9 and 6.2. In one embodiment, the tissue microenvironment cleavable linker is cleavable at a pH between about 6.0 and about 7.0, between about 6.2 and about 6.9, between about 6.5 and about 6.8, or between about 6.5 and about 6.7. In one embodiment, the tissue microenvironment cleavable linker is cleavable at a pH between about 5.5 and about 6.5, e.g., between 5.9 and 6.2. In one embodiment, the tissue microenvironment cleavable linker is cleavable at a hypoxic pH, e.g., a pH about 6.7 to 6.9, e.g., compared to a physiological pH of about 7.4. In some embodiments, the tissue microenvironment cleavable linker is cleavable is cleaved at a pH of no more than 74 no more than 70 no more than 69 no more than 68 no more than 6.7, no more than 6.6, no more than 6.5, no more than 6.4, no more than 6.3, no more than 6.2, no more than 6.1, no more than 6.0, no more than 5.5 or lower. In one embodiment, the tissue microenvironment cleavable linker is preferentially cleaved or degraded upon exposure to a first pH relative to a second pH. In one embodiment, the tissue microenvironment cleavable linker is cleaved or degraded at least 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, or 100 times faster upon exposure to a first pH relative to a second pH. In other embodiments, the tissue microenvironment cleavable linker shows a greater release or degradation rate at a first acidic pH (e.g., pH=6.7) relative to a second more basic pH (e.g., pH = 7.4). In one embodiment, ratio of release or degradation rate of the tissue microenvironment cleavable linker at pH=6.7 relative to pH = 7.4 is greater than 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3 or higher. In one embodiment, ratio of release or degradation rate of the tissue microenvironment cleavable linker at pH=6.7 relative to pH = 7.4 is greater than 2. In one embodiment, the tissue microenvironment cleavable linker shows increased pH- sensitivity in a hypoxic microenvironment, e.g., in a tumor, or fibrotic tissue. In some embodiments, the tissue microenvironment cleavable linker exhibits an increased release rate or increased release yield of the agent at a desired site (e.g., a tumor), e.g., relative to the release rate or release yield at another site. In one embodiment, the tissue microenvironment cleavable linker comprises an electron withdrawing group (e.g., an electron withdrawing group that enhances the cleavage rate or yield, e.g., upon exposure to a first set of conditions relative to a second set of conditions). In certain embodiments, at least one instance of M ¹ is M. In certain embodiments, at least one instance of the pharmaceutical agents is M. In certain embodiments, each instance of M is independently a pharmaceutical agent. The pharmaceutical agents include chemical compounds and mixtures of chemical compounds, e.g., small organic or inorganic molecules; saccharines; oligosaccharides; polysaccharides; biological macromolecules, e.g., peptides, proteins, and peptide analogs and derivatives; peptidomimetics; antibodies and antigen binding fragments thereof; nucleic acids; nucleic acid analogs and derivatives; an extract made from biological materials such as bacteria, plants, fungi, or animal cells; animal tissues; naturally occurring or synthetic compositions; and any combinations thereof. In some embodiments, the pharmaceutical agent is a small molecule. In some embodiments, the pharmaceutical agent is a peptide or protein. Exemplary pharmaceutical agents include, but are not limited to, those found in Harrison’s Principles of Internal Medicine , 13th Edition, Eds. T.R. Harrison et al. McGraw-Hill N.Y., NY; Physicians’ Desk Reference, 50th Edition, 1997, Oradell New Jersey, Medical Economics Co.; Pharmacological Basis of Therapeutics, 8th Edition, Goodman and Gilman, 1990; United States Pharmacopeia The National Formulary USP XII NF XVII 1990; current edition of Goodman and Oilman’s The Pharmacological Basis of Therapeutics ; and current edition of The Merck Index , the complete contents of all of which are incorporated herein by reference. In certain embodiments, each instance of M is independently a therapeutic agent or a diagnostic agent. In certain embodiments, at least one instance of M is a therapeutic agent. In certain embodiments, each instance of M is a therapeutic agent. In some embodiments, exemplary therapeutic agents include, but are not limited to, one or more of the agents listed in Paragraph 0148 of U.S. Patent No.9,381,253, incorporated by reference herein. In other embodiments, exemplary therapeutic agents include, but are not limited to, one or more of the therapeutic agents listed in WO 2013/169739, including the anti-hypertensive and/or a collagen modifying agents ("AHCM") disclosed, e.g., in Paragraphs 40-49, 283, 286-295; the microenviroment modulators disclosed, e.g., in Paragraphs 113-121, of WO 2013/169739, incorporated herein by reference. Examples of therapeutic agents also include, but are not limited to, antimicrobial agents, analgesics, antinflammatory agents, counterirritants, coagulation modifying agents, diuretics, sympathomimetics, anorexics, antacids and other gastrointestinal agents; antiparasitics, antidepressants, antihypertensives, anticholinergics, stimulants, antihormones, central and respiratory stimulants, drug antagonists, lipid-regulating agents, uricosurics, cardiac glycosides, electrolytes, ergot and derivatives thereof, expectorants, hypnotics and sedatives, antidiabetic agents, dopaminergic agents, antiemetics, muscle relaxants, para-sympathomimetics, anticonvulsants, antihistamines, beta-blockers, purgatives, antiarrhythmics, contrast materials, radiopharmaceuticals, antiallergic agents, tranquilizers, vasodilators, antiviral agents, and antineoplastic or cytostatic agents or other agents with anticancer properties, or a combination thereof. Other suitable therapeutic agents include contraceptives and vitamins as well as micro- and macronutrients. Still other examples include antiinfectives such as antibiotics and antiviral agents; analgesics and analgesic combinations; anorexics; antiheimintics; antiarthritics; antiasthmatic agents; anticonvulsants; antidepressants; antidiuretic agents; antidiarrleals; antihistamines; antiinflammatory agents; antimigraine preparations; antinauseants; antineoplastics; antiparkinsonism drugs; antipruritics; antipsychotics; antipyretics, antispasmodics; anticholinergics; sympathomimetics; xanthine derivatives; cardiovascular preparations including calcium channel blockers and beta-blockers such as pindolol and antiarrhythmics; antihypertensives; diuretics; vasodilators including general coronary, peripheral and cerebral; central nervous system stimulants; cough and cold preparations, including decongestants; hormones such as estradiol and other steroids, including corticosteroids; hypnotics; immunosuppressives; muscle relaxants; parasympatholytics; psychostimulants; sedatives; and tranquilizers; and naturally derived or genetically engineered proteins, polysaccharides, glycoproteins, or lipoproteins. In certain embodiments, at least one instance of M is an anti-cancer agent. In some embodiments, the anti-cancer agent is selected from the group consisting of abiraterone acetate, ABVD, ABVE, ABVE-PC, AC, AC-T, ADE, ado-trastuzumab emtansine, afatinib dimaleate, aldesleukin, alemtuzumab, anastrozole, arsenic trioxide, asparaginase erwinia chrysanthemi, axitinib, azacitidine, BEACOPP, belinostat, bendamustine hydrochloride, BEP, bevacizumab, bicalutamide, bleomycin, blinatumomab, bortezomib, bosutinib, brentuximab vedotin, busulfan, cabazitaxel, cabozantinib-s-malate, CAF, capecitabine, CAPOX, carboplatin, carboplatin-taxol, carfilzomibcarmustine, carmustine implant, ceritinib, cetuximab, chlorambucil, chlorambucil- prednisone, CHOP, cisplatin, clofarabine, CMF, COPP, COPP-ABV, crizotinib, CVP, cyclophosphamide, cytarabine, dabrafenib, dacarbazine, dactinomycin, dasatinib, daunorubicin hydrochloride, decitabine, degarelix, denileukin diftitox, denosumab, Dinutuximab, docetaxel, doxorubicin hydrochloride, doxorubicin hydrochloride liposome, enzalutamide, epirubicin hydrochloride, EPOCH, erlotinib hydrochloride, etoposide, etoposide phosphate, everolimus, exemestane, FEC, fludarabine phosphate, fluorouracil, FOLFIRI , FOLFIRI-BEVACIZUMAB, FOLFIRI-CETUXIMAB, FOLFIRINOX, FOLFOX, FU-LV, fulvestrant, gefitinib, gemcitabine hydrochloride, gemcitabine-cisplatin, gemcitabine-oxaliplatin, goserelin acetate, Hyper-CVAD, ibritumomab tiuxetan, ibrutinib, ICE, idelalisib, ifosfamide, imatinib mesylate, imiquimod, ipilimumab, irinotecan hydrochloride, ixabepilone, lanreotide acetate, lapatinib ditosylate, lenalidomide, lenvatinib, letrozole, leucovorin calcium, leuprolide acetate, liposomal cytarabine, lomustine, mechlorethamine hydrochloride, megestrol acetate, mercaptopurine, methotrexate, mitomycin c, mitoxantrone hydrochloride, MOPP, nelarabine, nilotinib, nivolumab, obinutuzumab, OEPA, ofatumumab, OFF, olaparib, omacetaxine mepesuccinate, OPPA, oxaliplatin, paclitaxel, paclitaxel albumin-stabilized nanoparticle formulation, PAD, palbociclib, pamidronate disodium, panitumumab, panobinostat, pazopanib hydrochloride, pegaspargase, peginterferon alfa-2b, peginterferon alfa-2b, pembrolizumab, pemetrexed disodium, pertuzumab, plerixafor, pomalidomide, ponatinib hydrochloride, pralatrexate, prednisone, procarbazine hydrochloride, radium 223 dichloride, raloxifene hydrochloride, ramucirumab, R-CHOP, recombinant HPV bivalent vaccine, recombinant human papillomavirus, nonavalent vaccine, recombinant human papillomavirus, quadrivalent vaccine, recombinant interferon alfa-2b, regorafenib, rituximab, romidepsin, ruxolitinib phosphate, siltuximab, sipuleucel-t, sorafenib tosylate, STANFORD V, sunitinib malate, TAC, tamoxifen citrate, temozolomide, temsirolimus, thalidomide, thiotepa, topotecan hydrochloride, toremifene, tositumomab and iodine I 131, tositumomab TPF trametinib trastuzumab VAMP vandetanib VEIP vemurafenib vinblastine sulfate, vincristine sulfate, vincristine sulfate liposome, vinorelbine tartrate, vismodegib, vorinostat, XELIRI, XELOX, ziv-aflibercept, and zoledronic acid. Anti-cancer agents encompass biotherapeutic anti-cancer agents as well as chemotherapeutic agents. Exemplary biotherapeutic anti-cancer agents include, but are not limited to, interferons, cytokines (e.g., tumor necrosis factor, interferon α, interferon γ), vaccines, hematopoietic growth factors, monoclonal serotherapy, immunostimulants and/or immunodulatory agents (e.g., IL-1, 2, 4, 6, or 12), immune cell growth factors (e.g., GM-CSF) and antibodies (e.g., HERCEPTIN (trastuzumab), T- DM1, AVASTIN (bevacizumab), ERBITUX (cetuximab), VECTIBIX (panitumumab), RITUXAN (rituximab), BEXXAR (tositumomab)). Exemplary chemotherapeutic agents include, but are not limited to, anti-estrogens (e.g., tamoxifen, raloxifene, and megestrol), LHRH agonists (e.g., goscrclin and leuprolide), anti-androgens (e.g., flutamide and bicalutamide), photodynamic therapies (e.g., vertoporfin (BPD-MA), phthalocyanine, photosensitizer Pc4, and demethoxy- hypocrellin A (2BA-2-DMHA)), nitrogen mustards (e.g., cyclophosphamide, ifosfamide, trofosfamide, chlorambucil, estramustine, and melphalan), nitrosoureas (e.g., carmustine (BCNU) and lomustine (CCNU)), alkylsulphonates (e.g., busulfan and treosulfan), triazenes (e.g., dacarbazine, temozolomide), platinum containing compounds (e.g., cisplatin, carboplatin, oxaliplatin), vinca alkaloids (e.g., vincristine, vinblastine, vindesine, and vinorelbine), taxoids (e.g., paclitaxel or a paclitaxel equivalent such as nanoparticle albumin-bound paclitaxel (ABRAXANE), docosahexaenoic acid bound-paclitaxel (DHA-paclitaxel, Taxoprexin), polyglutamate bound-paclitaxel (PG-paclitaxel, paclitaxel poliglumex, CT-2103, XYOTAX), the tumor-activated prodrug (TAP) ANG1005 (Angiopep-2 bound to three molecules of paclitaxel), paclitaxel-EC-1 (paclitaxel bound to the erbB2-recognizing peptide EC-1), and glucose- conjugated paclitaxel, e.g., 2'-paclitaxel methyl 2-glucopyranosyl succinate; docetaxel, taxol), epipodophyllins (e.g., etoposide, etoposide phosphate, teniposide, topotecan, 9- aminocamptothecin, camptoirinotecan, irinotecan, crisnatol, mytomycin C), anti-metabolites, DHFR inhibitors (e.g., methotrexate, dichloromethotrexate, trimetrexate, edatrexate), IMP dehydrogenase inhibitors (e.g., mycophenolic acid, tiazofurin, ribavirin, and EICAR), ribonuclotide reductase inhibitors (e.g., hydroxyurea and deferoxamine), uracil analogs (e.g., 5- fluorouracil (5-FU), floxuridine, doxifluridine, ratitrexed, tegafur-uracil, capecitabine), cytosine analogs (e.g., cytarabine (ara C), cytosine arabinoside, and fludarabine), purine analogs (e.g., mercaptopurine and Thioguanine), Vitamin D3 analogs (e.g., EB 1089, CB 1093, and KH 1060), isoprenylation inhibitors (e.g., lovastatin), dopaminergic neurotoxins (e.g., 1-methyl-4- phenylpyridinium ion), cell cycle inhibitors (e.g., staurosporine), actinomycin (e.g., actinomycin D, dactinomycin), bleomycin (e.g., bleomycin A2, bleomycin B2, peplomycin), anthracycline (eg daunorubicin doxorubicin pegylated liposomal doxorubicin idarubicin epirubicin pirarubicin, zorubicin, mitoxantrone), MDR inhibitors (e.g., verapamil), Ca2+ ATPase inhibitors (e.g., thapsigargin), imatinib, thalidomide, lenalidomide, tyrosine kinase inhibitors (e.g., axitinib (AG013736), bosutinib (SKI-606), cediranib (RECENTINTM, AZD2171), dasatinib (SPRYCEL®, BMS-354825), erlotinib (TARCEVA®), gefitinib (IRESSA®), imatinib (Gleevec®, CGP57148B, STI-571), lapatinib (TYKERB®, TYVERB®), lestaurtinib (CEP-701), neratinib (HKI-272), nilotinib (TASIGNA®), semaxanib (semaxinib, SU5416), sunitinib (SUTENT®, SU11248), toceranib (PALLADIA®), vandetanib (ZACTIMA®, ZD6474), vatalanib (PTK787, PTK/ZK), trastuzumab (HERCEPTIN®), bevacizumab (AVASTIN®), rituximab (RITUXAN®), cetuximab (ERBITUX®), panitumumab (VECTIBIX®), ranibizumab (Lucentis®), nilotinib (TASIGNA®), sorafenib (NEXAVAR®), everolimus (AFINITOR®), alemtuzumab (CAMPATH®), gemtuzumab ozogamicin (MYLOTARG®), temsirolimus (TORISEL®), ENMD-2076, PCI-32765, AC220, dovitinib lactate (TKI258, CHIR-258), BIBW 2992 (TOVOKTM), SGX523, PF-04217903, PF-02341066, PF-299804, BMS-777607, ABT- 869, MP470, BIBF 1120 (VARGATEF®), AP24534, JNJ-26483327, MGCD265, DCC-2036, BMS-690154, CEP-11981, tivozanib (AV-951), OSI-930, MM-121, XL-184, XL-647, and/or XL228), proteasome inhibitors (e.g., bortezomib (VELCADE)), mTOR inhibitors (e.g., rapamycin, temsirolimus (CCI-779), everolimus (RAD-001), ridaforolimus, AP23573 (Ariad), AZD8055 (AstraZeneca), BEZ235 (Novartis), BGT226 (Norvartis), XL765 (Sanofi Aventis), PF-4691502 (Pfizer), GDC0980 (Genetech), SF1126 (Semafoe) and OSI-027 (OSI)), oblimersen, gemcitabine, carminomycin, leucovorin, pemetrexed, cyclophosphamide, dacarbazine, procarbizine, prednisolone, dexamethasone, campathecin, plicamycin, asparaginase, aminopterin, methopterin, porfiromycin, melphalan, leurosidine, leurosine, chlorambucil, trabectedin, procarbazine, discodermolide, carminomycin, aminopterin, and hexamethyl melamine. In certain embodiments, the anti-cancer agent is abiraterone acetate (e.g., ZYTIGA), ABVD, ABVE, ABVE-PC, AC, AC-T, ADE, ado-trastuzumab emtansine (e.g., KADCYLA), afatinib dimaleate (e.g., GILOTRIF), aldesleukin (e.g., PROLEUKIN), alemtuzumab (e.g., CAMPATH), anastrozole (e.g., ARIMIDEX), arsenic trioxide (e.g., TRISENOX), asparaginase erwinia chrysanthemi (e.g., ERWINAZE), axitinib (e.g., INLYTA), azacitidine (e.g., MYLOSAR, VIDAZA), BEACOPP, belinostat (e.g., BELEODAQ), bendamustine hydrochloride (e.g., TREANDA), BEP, bevacizumab (e.g., AVASTIN), bicalutamide (e.g., CASODEX), bleomycin (e.g., BLENOXANE), blinatumomab (e.g., BLINCYTO), bortezomib (e.g., VELCADE), bosutinib (e.g., BOSULIF), brentuximab vedotin (e.g., ADCETRIS), busulfan (e.g., BUSULFEX, MYLERAN), cabazitaxel (e.g., JEVTANA), cabozantinib-s-malate (e.g., COMETRIQ), CAF, capecitabine (e.g., XELODA), CAPOX, carboplatin (e.g., PARAPLAT, PARAPLATIN) carboplatin taxol carfilzomib (eg KYPROLIS) carmustine (eg BECENUM, BICNU, CARMUBRIS), carmustine implant (e.g., GLIADEL WAFER, GLIADEL), ceritinib (e.g., ZYKADIA), cetuximab (e.g., ERBITUX), chlorambucil (e.g., AMBOCHLORIN, AMBOCLORIN, LEUKERAN, LINFOLIZIN), chlorambucil-prednisone, CHOP, cisplatin (e.g., PLATINOL, PLATINOL-AQ), clofarabine (e.g., CLOFAREX, CLOLAR), CMF, COPP, COPP-ABV, crizotinib (e.g., XALKORI), CVP, cyclophosphamide (e.g., CLAFEN, CYTOXAN, NEOSAR), cytarabine (e.g., CYTOSAR-U, TARABINE PFS), dabrafenib (e.g., TAFINLAR), dacarbazine (e.g., DTIC-DOME), dactinomycin (e.g., COSMEGEN), dasatinib (e.g., SPRYCEL), daunorubicin hydrochloride (e.g., CERUBIDINE), decitabine (e.g., DACOGEN), degarelix, denileukin diftitox (e.g., ONTAK), denosumab (e.g., PROLIA, XGEVA), Dinutuximab (e.g., UNITUXIN), docetaxel (e.g., TAXOTERE), doxorubicin hydrochloride (e.g., ADRIAMYCIN PFS, ADRIAMYCIN RDF), doxorubicin hydrochloride liposome (e.g., DOXIL, DOX-SL, EVACET, LIPODOX), enzalutamide (e.g., XTANDI), epirubicin hydrochloride (e.g., ELLENCE), EPOCH, erlotinib hydrochloride (e.g., TARCEVA), etoposide (e.g., TOPOSAR, VEPESID), etoposide phosphate (e.g., ETOPOPHOS), everolimus (e.g., AFINITOR DISPERZ, AFINITOR), exemestane (e.g., AROMASIN), FEC, fludarabine phosphate (e.g., FLUDARA), fluorouracil (e.g., ADRUCIL, EFUDEX, FLUOROPLEX), FOLFIRI , FOLFIRI-BEVACIZUMAB, FOLFIRI-CETUXIMAB, FOLFIRINOX, FOLFOX, FU-LV, fulvestrant (e.g., FASLODEX), gefitinib (e.g., IRESSA), gemcitabine hydrochloride (e.g., GEMZAR), gemcitabine-cisplatin, gemcitabine-oxaliplatin, goserelin acetate (e.g., ZOLADEX), Hyper-CVAD, ibritumomab tiuxetan (e.g., ZEVALIN), ibrutinib (e.g., IMBRUVICA), ICE, idelalisib (e.g., ZYDELIG), ifosfamide (e.g., CYFOS, IFEX, IFOSFAMIDUM), imatinib mesylate (e.g., GLEEVEC), imiquimod (e.g., ALDARA), ipilimumab (e.g., YERVOY), irinotecan hydrochloride (e.g., CAMPTOSAR), ixabepilone (e.g., IXEMPRA), lanreotide acetate (e.g., SOMATULINE DEPOT), lapatinib ditosylate (e.g., TYKERB), lenalidomide (e.g., REVLIMID), lenvatinib (e.g., LENVIMA), letrozole (e.g., FEMARA), leucovorin calcium (e.g., WELLCOVORIN), leuprolide acetate (e.g., LUPRON DEPOT, LUPRON DEPOT-3 MONTH, LUPRON DEPOT-4 MONTH, LUPRON DEPOT- PED, LUPRON, VIADUR), liposomal cytarabine (e.g., DEPOCYT), lomustine (e.g., CEENU), mechlorethamine hydrochloride (e.g., MUSTARGEN), megestrol acetate (e.g., MEGACE), mercaptopurine (e.g., PURINETHOL, PURIXAN), methotrexate (e.g., ABITREXATE, FOLEX PFS, FOLEX, METHOTREXATE LPF, MEXATE, MEXATE-AQ), mitomycin c (e.g., MITOZYTREX, MUTAMYCIN), mitoxantrone hydrochloride, MOPP, nelarabine (e.g., ARRANON), nilotinib (e.g., TASIGNA), nivolumab (e.g., OPDIVO), obinutuzumab (e.g., GAZYVA), OEPA, ofatumumab (e.g., ARZERRA), OFF, olaparib (e.g., LYNPARZA), omacetaxine mepesuccinate (eg SYNRIBO) OPPA OTX 015 oxaliplatin (eg ELOXATIN), paclitaxel (e.g., TAXOL), paclitaxel albumin-stabilized nanoparticle formulation (e.g., ABRAXANE), PAD, palbociclib (e.g., IBRANCE), pamidronate disodium (e.g., AREDIA), panitumumab (e.g., VECTIBIX), panobinostat (e.g., FARYDAK), pazopanib hydrochloride (e.g., VOTRIENT), pegaspargase (e.g., ONCASPAR), peginterferon alfa-2b (e.g., PEG-INTRON), peginterferon alfa-2b (e.g., SYLATRON), pembrolizumab (e.g., KEYTRUDA), pemetrexed disodium (e.g., ALIMTA), pertuzumab (e.g., PERJETA), plerixafor (e.g., MOZOBIL), pomalidomide (e.g., POMALYST), ponatinib hydrochloride (e.g., ICLUSIG), pralatrexate (e.g., FOLOTYN), prednisone, procarbazine hydrochloride (e.g., MATULANE), radium 223 dichloride (e.g., XOFIGO), raloxifene hydrochloride (e.g., EVISTA, KEOXIFENE), ramucirumab (e.g., CYRAMZA), R-CHOP, recombinant HPV bivalent vaccine (e.g., CERVARIX), recombinant human papillomavirus (e.g., HPV) nonavalent vaccine (e.g., GARDASIL 9), recombinant human papillomavirus (e.g., HPV) quadrivalent vaccine (e.g., GARDASIL), recombinant interferon alfa-2b (e.g., INTRON A), regorafenib (e.g., STIVARGA), rituximab (e.g., RITUXAN), romidepsin (e.g., ISTODAX), ruxolitinib phosphate (e.g., JAKAFI), siltuximab (e.g., SYLVANT), sipuleucel-t (e.g., PROVENGE), sorafenib tosylate (e.g., NEXAVAR), STANFORD V, sunitinib malate (e.g., SUTENT), TAC, tamoxifen citrate (e.g., NOLVADEX, NOVALDEX), temozolomide (e.g., METHAZOLASTONE, TEMODAR), temsirolimus (e.g., TORISEL), thalidomide (e.g., SYNOVIR, THALOMID), thiotepa, topotecan hydrochloride (e.g., HYCAMTIN), toremifene (e.g., FARESTON), tositumomab and iodine I 131 tositumomab (e.g., BEXXAR), TPF, trametinib (e.g., MEKINIST), trastuzumab (e.g., HERCEPTIN), VAMP, vandetanib (e.g., CAPRELSA), VEIP, vemurafenib (e.g., ZELBORAF), vinblastine sulfate (e.g., VELBAN, VELSAR), vincristine sulfate (e.g., VINCASAR PFS), vincristine sulfate liposome (e.g., MARQIBO), vinorelbine tartrate (e.g., NAVELBINE), vismodegib (e.g., ERIVEDGE), vorinostat (e.g., ZOLINZA), XELIRI, XELOX, ziv-aflibercept (e.g., ZALTRAP), or zoledronic acid (e.g., ZOMETA), or a pharmaceutically acceptable salt thereof. In certain embodiments, at least one instance of the therapeutic agent is a bromodomain inhibitor. In certain embodiments, at least one instance of the therapeutic agent is a bromo and extra terminal protein (BET) inhibitor. In certain embodiments, at least one instance of the therapeutic agent is a bromodomain-containing protein 2 (BRD2) inhibitor, bromodomain- containing protein 3 (BRD3) inhibitor, bromodomain-containing protein 4 (BRD4) inhibitor, TBP (TATA box binding protein)-associated factor protein (TAF) (e.g., TAF1 or TAF1L) inhibitor, CREB-binding protein (CBP) inhibitor, or E1A binding protein p300 (EP300) inhibitor. In certain embodiments, at least one instance of M is a PARP inhibitor, ALK inhibitor, or STING ligand. In certain embodiments, at least one instance of the therapeutic agent is MMAE In certain embodiments at least one instance of the therapeutic agent is PTX In certain embodiments, at least one instance of the therapeutic agent is DOX. In certain embodiments, at least one instance of the therapeutic agent is SN-38. In certain embodiments, at least one instance of the therapeutic agent is a proteolysis- targeting chimera (PROTAC). In certain embodiments, at least one instance of the PROTAC is ARV771, ARV825, ARV766, ARV110, ARV471, AC682, CC-94676, DT2216, FHD-609, KT- 474, KT-413, KT-333, NX-2127, NX-5948, CFT8634, CFT8919, or CG001419, or a pharmaceutically acceptable salt thereof. In certain embodiments, at least one instance of M is a prophylactic agent. In certain embodiments, each instance of M is a prophylactic agent. Prophylactic agents that can be included in the conjugates of the invention include, but are not limited to, antibiotics, nutritional supplements, and vaccines. Vaccines may comprise isolated proteins or peptides, inactivated organisms and viruses, dead organisms and viruses, genetically altered organisms or viruses, and cell extracts. Prophylactic agents may be combined with interleukins, interferon, cytokines, and adjuvants such as cholera toxin, alum, Freund's adjuvant. In certain embodiments, at least one instance of M is a diagnostic agent. In certain embodiments, each instance of M is a diagnostic agent. Exemplary diagnostic agents include, but are not limited to, fluorescent molecules; gases; metals; imaging agents, such as commercially available imaging agents used in positron emissions tomography (PET), computer assisted tomography (CAT), single photon emission computerized tomography, x-ray, fluoroscopy, and magnetic resonance imaging (MRI); and contrast agents. Examples of suitable materials for use as contrast agents in MRI include gadolinium chelates, as well as iron, magnesium, manganese, copper, and chromium. Examples of materials useful for CAT and x-ray imaging include iodine- based materials. In certain embodiments, the diagnostic agent is used in magnetic resonance imaging (MRI), such as iron oxide particles or gadolinium complexes. Gadolinium complexes that have been approved for clinical use include gadolinium chelates with DTPA, DTPA-BMA, DOTA and HP-DO3A which are reviewed in Aime, et al. (Chemical Society Reviews (1998), 27:19-29), the entire teachings of which are incorporated herein by reference. In certain embodiments, the diagnostic agent is a metal, inorganic compound, organometallic compound, organic compound, or salt thereof. In certain embodiments, the imaging agent contains a metal selected from the group consisting of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, gadolinium, gallium, thallium, and barium. In certain embodiments the diagnostic agent is an organic compound In certain embodiments the diagnostic agent is metal-free. In certain embodiments, the diagnostic agent is a metal-free organic compound. In certain embodiments, the imaging agent is a magnetic resonance imaging (MRI) agent. In certain embodiments, the MRI agent is gadolinium. In certain embodiments, the MRI agent is a nitroxide radical-containing compound. In certain embodiments, the imaging agent is a nuclear medicine imaging agent. In certain embodiments, the nuclear medicine imaging agent is selected from the group consisting of ⁶⁴ Cu diacetyl-bis(N ⁴ -methylthiosemicarbazone) ( ⁶⁴ Cu-ASTM), ¹⁸ F-fluorodeoxyglucose (FDG), ¹⁸ F- fluoride, 3'-deoxy-3'-[ ¹⁸ F]fluorothymidine (FLT), ¹⁸ F-fluoromisonidazole (FMISO), gallium, technetium-99m, and thallium. In certain embodiments, the imaging agent is radiographic imaging agent. In certain embodiments, the radiographic imaging agent is selected from the group consisting of barium, gastrografin, and iodine contrast agent. In certain embodiments, the imaging agent the diagnostic agent is a radical-containing compound. In certain embodiments, the imaging agent is a nitroxide radical-containing compound. In certain embodiments, the imaging agent the diagnostic agent is of the formula: . In certain embodiments, the imaging agent the diagnostic agent is an organic compound. In certain embodiments, the imaging agent is a salt of an organic compound. In certain embodiments, the imaging agent the diagnostic agent is of the formula: . In certain embodiments, the diagnostic agent may comprise a fluorescent molecule, a metal chelate, a contrast agent, a radionuclide, or a positron emission tomography (PET) imaging agent, an infrared imaging agent, a near-IR imaging agent, a computer assisted tomography (CAT) imaging agent, a photon emission computerized tomography imaging agent, an X-ray imaging agent, or a magnetic resonance imaging (MRI) agent. In some embodiments, the diagnostic agent is a fluorescent molecule. In some embodiments, the fluorescent molecule comprises an acridine dye, a cyanine dye, a rhodamine dye, a BODIPY dye, a fluorescein dye, a dansyl dye, an Alexa dye, an atto dye, a quantum dot, or a fluorescent protein. In some embodiments, the fluorescent molecule is a cyanine dye (e.g., Cy3, Cy 3.5, Cy5, Cy5.5, Cy7, or Cy7.5). In some embodiments, the diagnostic agent is an MRI agent (e.g., a contrast agent). Examples of suitable materials for use as MRI agents (e.g., contrast agents) include gadolinium chelates, as well as iron, magnesium, manganese, copper, and chromium. In some embodiments, the diagnostic agent is a CAT imaging agent or an X-ray imaging agent. Examples of materials useful for CAT and X-ray imaging include iodine-based materials. In some embodiments, the diagnostic agent is a PET imaging agent. Examples of suitable PET imaging agents include compounds and compositions comprising the positron emitting radioisotopoes ¹⁸ F, ¹⁵ O, ¹³ N, ¹¹ C, ⁸² Rb, ⁶⁴ Cu, and ⁶⁸ Ga, e.g., fludeoxyglucose ( ¹⁸ F-FDG), ⁶⁸ Ga- DOTA-psuedopeptides (e.g., ⁶⁸ Ga-DOTA-TOC), ¹¹ C-metomidate, ¹¹ C-acetate, ¹¹ C-methionine, ¹¹ C-choline, ¹⁸ F-fluciclovine, ¹⁸ F-fluorocholine, ¹⁸ F-fluorodeoxysorbitol, ¹⁸ F-3’-fluoro-3’- deoxythymidine, ¹¹ C-raclopride, and ¹⁸ F-desmethoxyfallypride. In some embodiments, the diagnostic agent is a near-IR imaging agent. Examples of near- IR imaging agents include Pz 247, DyLight 750, DyLight 800, cyanine dyes (e.g., Cy5, Cy5.5, Cy7), AlexaFluor 680, AlexaFluor 750, IRDye 680, IRDye 800CW, and Kodak X-SIGHT dyes. In some embodiments, the agent can be a radionuclide, e.g., for use as a therapeutic, diagnostic, or prognostic agents. Among the radionuclides used, gamma-emitters, positron- emitters, and X-ray emitters are suitable for diagnostic and/or therapy, while beta emitters and alpha-emitters may also be used for therapy. Suitable radionuclides for forming use with various embodiments of the present invention include, but are not limited to, ¹²³ I, ¹²⁵ I, ¹³⁰ I, ¹³¹ I, ¹³³ I, ¹³⁵ I, ⁴⁷ Sc, ⁷² As, ⁷² Sc, ⁹⁰ Y, ⁸⁸ Y, ⁹⁷ Ru, ¹⁰⁰ Pd, ^101m Rh, ¹¹⁹ Sb, ¹²⁸ Ba, ¹⁹⁷ Hg, ²¹¹ At, ²¹² Bi, ²¹² Pb, ¹⁰⁹ Pd, ¹¹¹ In, ⁶⁷ Ga, ⁶⁸ Ga, ⁶⁷ Cu, ⁷⁵ Br, ⁷⁷ Br, ^99m Tc, ¹⁴ C, ¹³ N, ¹⁵ O, ³² P, ³³ P, or ¹⁸ F. In certain embodiments, at least one instance of the diagnostic agent is a contrast agent. In certain embodiments, at least one instance of the contrast agent is a magnetic-resonance signal enhancing agent, X-ray attenuating agent, ultrasound scattering agent, or ultrasound frequency shifting agent. In certain embodiments, M being a pharmaceutical agent refers to M being a monovalent radical of the pharmaceutical agent. In certain embodiments, the monovalent radical of the pharmaceutical agent is formed by removing a hydrogen atom from the moiety HV of the pharmaceutical agent. In certain embodiments, V is a carbon atom. In certain embodiments, V is a heteroatom. In certain embodiments, V is an oxygen atom. In certain embodiments, V is a sulfur atom. In certain embodiments, V is a nitrogen atom. In certain embodiments, the monovalent radical of the pharmaceutical agent is formed further by changing the atom V of the pharmaceutical agent to substituted or unsubstituted U, wherein each of V and U is a heteroatom, and V and U are different from each other. In certain embodiments, at least two instances of M of at least one instance of the monomers, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, are different from each other. In certain embodiments, at least one instance of M of a first instance of the monomers, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, is different from at least one instance of M of a second instance of the monomers, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co- crystal thereof. In certain embodiments, all instances of M are the same. In certain embodiments, each instance of m is 1. In certain embodiments, at least one instance of m is 1. In certain embodiments, each instance of m is 1. In certain embodiments, at least one instance of m is an integer from 2 to 10, inclusive. In certain embodiments, at least one instance of m is 2, 3, 4, or 5. In certain embodiments, the end-functionalized polymer comprises between 10 and 1,000 (e.g., between 10 and 30, between 30 and 100, between 100 and 300, or between 300 and 1,000), inclusive, instances of M. In certain embodiments, each instance of R ^B is independently H, F, Cl, or –CH3. In certain embodiments, each instance of R ^B is H. In certain embodiments, each instance of b is independently 0, 1, 2, 3, or 4. In certain embodiments, each instance of b is independently 1, 2, 3, or 4. In certain embodiments, each instance of b is 2. In certain embodiments, each instance of e is independently 1, 2, 3, or 4. In certain embodiments, each instance of e is 1. In certain embodiments, each instance of e is independently 2, 3, or 4. In certain embodiments, at least one instance of X is OR ^C . In certain embodiments, each instance of X is OR ^C . In certain embodiments, at least one instance of X is N(R ^D )2. In certain embodiments, each instance of X is N(R ^D )2. In certain embodiments, each instance of R ^C is independently hydrogen, substituted or unsubstituted, C _1-6 alkyl, an oxygen protecting group, or a leaving group; and at least one instance of R ^D is hydrogen, substituted or unsubstituted, C1-6 alkyl, or a nitrogen protecting group. In certain embodiments, each instance of X is –OR ^C , wherein R ^C is an oxygen protecting group or a leaving group. In certain embodiments, each instance of X is –OH. In certain embodiments, at least one instance of X is . In certain embodiments, each instance of X is . In certain embodiments, each instance of X is wherein each instance of n is independently an integer from 40 to 100, inclusive; and each instance of R ^F is independently hydrogen or unsubstituted C _1-6 alkyl. In certain embodiments, each instance of R ^C or at least one instance of R ^D is substituted or unsubstituted, C ₅₀ - ₁₀₀₀ heteroalkyl. In certain embodiments, each instance of R ^C or at least one instance , wherein: each instance of n is independently an integer from 1 to 300, inclusive; and each instance of R ^F is independently hydrogen, substituted or unsubstituted, C1-6 alkyl, or an oxygen protecting group. In certain embodiments, at least one instance of n is an integer from 10 to 30, from 30 to 100, from 100 to 300, or from 300 to 1,000, inclusive. In certain embodiments, at least one instance of n is an integer from 40 to 100, inclusive. In certain embodiments, at least one instance of n is an integer from 50 to 80, inclusive. In certain embodiments, each instance of R ^C or at least one instance of R ^D is , wherein: each instance of u is independently 1, 2, 3, 4, 5, or 6; each instance of R ^G is independently hydrogen, halogen, or substituted or unsubstituted, C _1-6 alkyl; each instance of v is independently an integer from 1 to 300, inclusive; and each instance of R ^F is independently hydrogen, substituted or unsubstituted, C1-6 alkyl, or an oxygen protecting group. In certain embodiments, at least one instance of R ^D is substituted or unsubstituted, C _1-1000 heteroalkyl, e.g., unsubstituted, C40-400 heteroalkyl. In certain embodiments, at least one instance of R ^D is –(CH2CH2O)30-200–H or –(CH2CH2O)30-200–(substituted or unsubstituted, C1-6 alkyl). In certain embodiments, at least one instance of R ^D is –(CH ₂ CH ₂ O) _10-30 –H, –(CH ₂ CH ₂ O) _10-30 – (substituted or unsubstituted, C1-6 alkyl), –(CH2CH2O)30-100–H, –(CH2CH2O)30-100–(substituted or unsubstituted, C1-6 alkyl), –(CH2CH2O)100-300–H, –(CH2CH2O)100-300–(substituted or unsubstituted, C _1-6 alkyl), –(CH ₂ CH ₂ O) _300-1000 –H, or –(CH ₂ CH ₂ O) _300-1000 –(substituted or unsubstituted, C _1-6 alkyl). In certain embodiments, . The monomers may be described by a number of properties, including molecular weight and hydrodynamic diameter. In some embodiments, the molecular weight of the monomer is between about 1 kDa and about 10 kDa, e.g., between about 2 kDa and about 8 kDa or about 3 kDa and about 6 kDa, e.g., as detected by mass spectrometry. In some embodiments, the molecular weight of the monomer is between about 3 kDa and about 6 kDa. In some embodiments, the molecular weight of the monomer is about 2 kDa, about 3 kDa, about 4 kDa, about 5 kDa, or about 6 kDa. In some embodiments, the hydrodynamic diameter of the monomer is between about 0.5 nm and about 3 nm, e.g., about 1 nm and about 2 nm, e.g., as detected by dynamic light scattering. In another aspect, the present disclosure provides a conjugate of Formula (IV’): (IV’), or a tautomer, isotopically labeled conjugate, or salt thereof, wherein: each instance of B ¹ is a polymer, wherein each instance of the polymer comprises independently one or more pharmaceutical agents; each instance of L ¹ is independently substituted or unsubstituted, C _1-1000 alkylene, substituted or unsubstituted, C _2-1000 alkenylene, substituted or unsubstituted, C _2-1000 alkynylene, substituted or unsubstituted, C1-1000 heteroalkylene, substituted or unsubstituted, C2-1000 heteroalkenylene, or substituted or unsubstituted, C _2-1000 heteroalkynylene; optionally wherein one or more backbone carbon atoms of the C _1-1000 alkylene, C _2- 1000 alkenylene, C2-1000 alkynylene, C1-1000 heteroalkylene, C2-1000 heteroalkenylene, or C2- 1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits; each instance of E is independently a moiety formed by reacting under suitable conditions an instance of E ¹ with an instance of E ² ; each instance of E ¹ is independently a thiophile, a first click-chemistry handle, a nucleophile, an electrophile, or a leaving group, H, halogen, substituted or unsubstituted, C1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, – C(=O)R ^a , –C(=O)OR ^a , –C(=O)N(R ^a )2, –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a )2, –NO2, – N ₃ , –NR ^a C(=O)R ^a , –NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a ) ₂ , –NR ^a C(=NR ^a )R ^a , –NR ^a C(=NR ^a )OR ^a , – NR ^a C(=NR ^a )N(R ^a )2, –OC(=O)R ^a , –OC(=O)OR ^a , –OC(=O)N(R ^a )2, –OC(=NR ^a )R ^a , – OC(=NR ^a )OR ^a , –OC(=NR ^a )N(R ^a )2, –NR ^a S(=O)2R ^a , –NR ^a S(=O)2OR ^a , –NR ^a S(=O)2N(R ^a )2, – OS(=O)R ^a , –OS(=O)OR ^a , –OS(=O)N(R ^a ) ₂ , –S(=O)R ^a , –S(=O)OR ^a , –S(=O)N(R ^a ) ₂ , –OS(=O) ₂ R ^a , –OS(=O)2OR ^a , –OS(=O)2N(R ^a )2, –S(=O)2R ^a , –S(=O)2OR ^a , –S(=O)2N(R ^a )2, or –P(=O)(R ^a )2; each instance of E ² is independently –SH, a second click-chemistry handle, an electrophile, a nucleophile, or a leaving group, H, halogen, substituted or unsubstituted, C _1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, – C(=O)R ^a , –C(=O)OR ^a , –C(=O)N(R ^a ) ₂ , –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a ) ₂ , –NO ₂ , – N3, –NR ^a C(=O)R ^a , –NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a )2, –NR ^a C(=NR ^a )R ^a , –NR ^a C(=NR ^a )OR ^a , – NR ^a C(=NR ^a )N(R ^a )2, –OC(=O)R ^a , –OC(=O)OR ^a , –OC(=O)N(R ^a )2, –OC(=NR ^a )R ^a , – OC(=NR ^a )OR ^a , –OC(=NR ^a )N(R ^a ) ₂ , –NR ^a S(=O) ₂ R ^a , –NR ^a S(=O) ₂ OR ^a , –NR ^a S(=O) ₂ N(R ^a ) ₂ , – OS(=O)R ^a , –OS(=O)OR ^a , –OS(=O)N(R ^a )2, –S(=O)R ^a , –S(=O)OR ^a , –S(=O)N(R ^a )2, –OS(=O)2R ^a , –OS(=O)2OR ^a , –OS(=O)2N(R ^a )2, –S(=O)2R ^a , –S(=O)2OR ^a , –S(=O)2N(R ^a )2, or –P(=O)(R ^a )2; each instance of R ^a is independently H, substituted or unsubstituted, C _1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, a nitrogen protecting group when attached to a nitrogen atom, an oxygen protecting group when attached to an oxygen atom, or a sulfur protecting group when attached to a sulfur atom, or two instances of R ^a attached to a nitrogen atom are joined with the nitrogen atom to form substituted or unsubstituted heterocyclyl or substituted or unsubstituted heteroaryl; n1 is an integer between 1 and 20, inclusive; and A ¹ is a peptide, protein, nucleoprotein, mucoprotein, lipoprotein, glycoprotein, or polynucleotide. In certain embodiments, Formula (IV’) is Formula (IV). In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C1-30 alkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C30- ₁₀₀ alkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C _100-300 alkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C300-1000 alkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C1-30 heteroalkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C30-100 heteroalkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C100-300 heteroalkylene. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C _300-1000 heteroalkylene. In certain embodiments, optionally wherein one, two, three, four, or five backbone carbon atoms of the C1-1000 alkylene, C2-1000 alkenylene, C2-1000 alkynylene, C1-1000 heteroalkylene, C2-1000 heteroalkenylene, or C _2-1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C1-30 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _1-30 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C30-100 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C30-100 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C100-300 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _100-300 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C300- 1000 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C300-1000 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C1-30 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _1-30 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C30-100 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _30-100 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C100-300 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C100-300 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C300- ₁₀₀₀ heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _300-1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C1-1000 alkylene or substituted or unsubstituted, C1-1000 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _1-1000 alkylene or C _1-1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ¹ is substituted or unsubstituted, C _3-400 alkylene or substituted or unsubstituted, C2-400 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C3-400 alkylene or C2-400 heteroalkylene are independently replaced with substituted or unsubstituted, monocyclic, 3- to 10-membered carbocyclylene, substituted or unsubstituted, monocyclic, 3- to 10-membered heterocyclylene, substituted or unsubstituted phenyl, or substituted or unsubstituted, monocyclic, 5- to 6-membered heteroarylene, as valency permits. In certain embodiments, the optional substituents included in at least one instance of L ¹ are independently halogen (e.g., F), unsubstituted C1-6 alkyl, C1-6 alkyl substituted with one or more halogen (e.g., F), –O–(unsubstituted C1-6 alkyl), –O–(C1-6 alkyl substituted with one or more halogen (e.g., F)), or oxo. In certain embodiments, the carbocyclylene or heterocyclylene included in at least one instance of L ¹ is monocyclic and 3- to 10-membered. In certain embodiments, the arylene included in at least one instance of L ¹ is phenylene. In certain embodiments, the heteroarylene included in at least one instance of L ¹ is monocyclic and 5- to 6-membered. In certain embodiments, at least one instance of L ¹ is independently , wherein: each instance of q is independently an integer from 1 to 10, inclusive; each instance of r1 is independently an integer from 2 to 40, inclusive; each instance of s is independently 0 or 1; each instance of t is independently an integer from 0 to 10, inclusive; and the attachment point marked with is attached to E ¹ or E. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _1-30 alkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C30- 100 alkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _100-300 alkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _300-1000 alkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C1-30 heteroalkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _30-100 heteroalkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C100-300 heteroalkylene. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C300-1000 heteroalkylene. In certain embodiments, optionally wherein one, two, three, four, or five backbone carbon atoms of the C1-1000 alkylene, C2-1000 alkenylene, C2-1000 alkynylene, C1-1000 heteroalkylene, C2-1000 heteroalkenylene, or C2-1000 heteroalkynylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C1-30 alkylene optionally wherein one two or three backbone carbon atoms of the C130 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _30-100 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C30-100 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C100-300 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C _100-300 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _300- 1000 alkylene, optionally wherein one, two, or three backbone carbon atoms of the C300-1000 alkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C1-30 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _1-30 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _30-100 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C30-100 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C100-300 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C _100-300 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _300- 1000 heteroalkylene optionally wherein one two or three backbone carbon atoms of the C3001000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _1-1000 alkylene or substituted or unsubstituted, C1-1000 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C1-1000 alkylene or C1-1000 heteroalkylene are independently replaced with substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, as valency permits. In certain embodiments, at least one instance of L ⁵ is substituted or unsubstituted, C _3-400 alkylene or substituted or unsubstituted, C _2-400 heteroalkylene, optionally wherein one, two, or three backbone carbon atoms of the C3-400 alkylene or C2-400 heteroalkylene are independently replaced with substituted or unsubstituted, monocyclic, 3- to 10-membered carbocyclylene, substituted or unsubstituted, monocyclic, 3- to 10-membered heterocyclylene, substituted or unsubstituted phenyl, or substituted or unsubstituted, monocyclic, 5- to 6-membered heteroarylene, as valency permits. In certain embodiments, the optional substituents included in at least one instance of L ⁵ are independently halogen (e.g., F), unsubstituted C1-6 alkyl, C1-6 alkyl substituted with one or more halogen (e.g., F), –O–(unsubstituted C1-6 alkyl), –O–(C1-6 alkyl substituted with one or more halogen (e.g., F)), or oxo. In certain embodiments, the carbocyclylene or heterocyclylene included in at least one instance of L ⁵ is monocyclic and 3- to 10-membered. In certain embodiments, the arylene included in at least one instance of L ⁵ is phenylene. In certain embodiments, the heteroarylene included in at least one instance of L ⁵ is monocyclic and 5- to 6-membered. In certain embodiments, at least one instance of L ⁵ is independently , wherein: each instance of X ² is independently –O–, –S–, –S–S–, –NH–, –C(=O)–, –C(=O)–O–, – C(=O)–NH–, –O–C(=O)–, –NH–C(=O)–, –O–C(=O)–O–, –O–C(=O)–NH–, –NH–C(=O)–O–, or –NH–C(=O)–NH–; each instance of X ³ is independently –O–, –S–, –S–S–, –NH–, –C(=O)–, –C(=O)–O–, – C(=O)–NH–, –O–C(=O)–, –NH–C(=O)–, –O–C(=O)–O–, –O–C(=O)–NH–, –NH–C(=O)–O–, or –NH–C(=O)–NH–; each instance of q is independently an integer from 1 to 10, inclusive; each instance of r1 is independently an integer from 2 to 40, inclusive; each instance of s is independently 0 or 1; each instance of t is independently an integer from 0 to 10, inclusive; and the attachment point marked with is attached to E ² or E. In certain embodiments, n1 is an integer between 1 and 10, inclusive. In certain embodiments, n1 is 1, 2, 3, 4, 5, or 6. In certain embodiments, n1 is 1, 2, or 3. In certain embodiments, n1 is 1 or 2. In certain embodiments, n1 is 1. In certain embodiments, n1 is 2. In certain embodiments, n1 is 3. In certain embodiments, the conjugate is a mixture of at least a conjugate where n1 is 1 and a conjugate where n1 is 2. In certain embodiments, the conjugate is a mixture of at least two of: a conjugate where n1 is 1, a conjugate where n1 is 2, and a conjugate where n1 is 3. In certain embodiments, the conjugate is purified so that between 50% and 70%, between 70% and 90%, between 90% and 95%, between 95% and 99%, or between 99% and 99.9% of all instances of n1 are the same. In certain embodiments, the conjugate is purified so that between 50% and 70%, between 70% and 90%, between 90% and 95%, between 95% and 99%, or between 99% and 99.9% of all instances of n1 are 1. In certain embodiments, the conjugate is purified so that between 50% and 70%, between 70% and 90%, between 90% and 95%, between 95% and 99%, or between 99% and 99.9% of all instances of n1 are 2. In certain embodiments, the conjugate is purified so that between 50% and 70%, between 70% and 90%, between 90% and 95%, between 95% and 99%, or between 99% and 99.9% of all instances of n1 are 3. In certain embodiments, A ¹ is an antibody. In certain embodiments, A ¹ is an immunoglobulin G (IgG). In certain embodiments, A ¹ is an IgG1, IgG2, IgG3, or IgG4. In certain embodiments, A ¹ is an immunoglobulin A (IgA), immunoglobulin D (IgD), immunoglobulin E (IgE), or immunoglobulin M (IgM). In certain embodiments, A ¹ is IgA1 or IgA2, In certain embodiments, A ¹ is an anti-HER2 antibody (e.g., trastuzumab) or anti-MUC1 antibody. In certain embodiments, A ¹ is an anti-oncoprotein antibody, and the oncoprotein is an oncoprotein of the cancer described herein. In certain embodiments, the antibody is a monoclonal antibody. In certain embodiments, the antibody is a polyclonal antibody. In certain embodiments, the antibody is a humanized antibody. In certain embodiments, A ¹ is a peptide or protein. In certain embodiments, A ¹ is a peptide or protein and comprises between 3 and 10, between 10 and 30, between 30 and 100, between 100 and 300, between 300 and 1,000, between 1,000 and 3,000, or between 3,000 and 10,000, inclusive, amino acids. In certain embodiments, E ¹ is a thiophile. In certain embodiments, E , (substituted or unsubstituted phenyl or substituted or unsubstituted, C _1-6 alkyl). In certain embodiments, E ¹ is –C(=O)OH. In certain embodiments, E ¹ is a first click- chemistry handle. In certain embodiments, E ¹ is –N3. In certain embodiments, E ¹ is substituted or unsubstituted nitrone. In certain embodiments, E ¹ is trans-cyclooctenyl, e.g., . In certain embodiments, E ¹ is substituted or unsubstituted 1,2,4,5-tetrazinyl. In certain embodiments, E ¹ is , wherein R ¹⁹ is H, halogen, unsubstituted C1-6 alkyl, or –O–(unsubstituted C1-6 alkyl). In certain embodiments, E ¹ is substituted or unsubstituted tetrazolyl. In certain embodiments, E ¹ is an electrophile. In certain embodiments, E ¹ is a leaving group. In certain embodiments, E ¹ is H. In certain embodiments, E ¹ is a polymerization handle. In certain embodiments, E ¹ is an addition polymerization handle or condensation polymerization handle. In certain embodiments, E ¹ is a metathesis polymerization handle. In certain embodiments, E ¹ is substituted or unsubstituted C _2-6 alkenyl or substituted or unsubstituted C2-6 alkynyl. In certain embodiments, E ¹ is –OH, –NH2, –C(=O)OH, or –C(=O)H. In certain embodiments, E ¹ is a nucleophile, an electrophile, a leaving group, substituted or unsubstituted C _2-6 alkenyl, substituted or unsubstituted C _2-6 alkynyl, –OH, –SH, –NHR ^a , –N ₃ , – C(=O)OH, –C(=O)N(R ^a )2, –C(=NR ^a )OH, –S(=O)OH, –S(=O)2OH, –C(=O)–(a leaving group), – C(=NR ^a )–(a leaving group), –S(=O)–(a leaving group), or –S(=O)2–(a leaving group). In certain embodiments, E ¹ is –N ₃ , substituted or unsubstituted 1,2,4,5-tetrazinyl, or substituted or unsubstituted tetrazolyl. In certain embodiments, E ² is –SH. In certain embodiments, E ² is a click-chemistry handle. In certain embodiments, E ² is C≡C. In certain embodiments, E ² is –C≡CH. In certain embodiments, E ² is substituted or unsubstituted, monocyclic, bicyclic, or tricyclic cycloalkynyl. In certain embodiments, E ² is substituted or unsubstituted, cyclooctynyl or azacyclooctynyl. In certain embodiments, E ² is substituted or unsubstituted, dibenzocyclooctynyl or dibenzo-5- azacyclooctynyl. In certain embodiments, . certain embodiments, E ² is , wherein R ¹⁹ is H, halogen, unsubstituted C1-6 alkyl, or –O–(unsubstituted C _1-6 alkyl). In certain embodiments, R ¹⁹ is –CH ₃ . In certain embodiments, E ² is non-aromatic C=C. In certain embodiments, E ² is substituted or unsubstituted, monocyclic, bicyclic, or tricyclic, trans-cycloalkenyl. In certain embodiments, E ² is trans-cyclooctenyl, e.g., oxanorbornenyl, or 7-azanorbornenyl. In certain embodiments, E ² is substituted or unsubstituted, norbornadienyl, 7-oxanorbornadienyl, or 7-azanorbornadienyl. In certain embodiments, E ² is a nucleophile, an electrophile, a leaving group, substituted or unsubstituted C2-6 alkenyl, substituted or unsubstituted C _2-6 alkynyl, –OH, –SH, –NHR ^a , –N ₃ , –C(=O)OH, –C(=O)N(R ^a ) ₂ , – C(=NR ^a )OH, –S(=O)OH, –S(=O) ₂ OH, –C(=O)–(a leaving group), –C(=NR ^a )–(a leaving group), –S(=O)–(a leaving group), or –S(=O)2–(a leaving group). In certain embodiments, E ² is C≡C or non-aromatic C=C. In certain embodiments, certain embodiments, E ¹ is trans-cycloocteny In certain trans- cyclooctenyl, e.g., . In certain embodiments, E ¹ is –N3, substituted or unsubstituted 1,2,4,5-tetrazinyl, or substituted or unsubstituted tetrazolyl, and E ² is C≡C or non-aromatic C=C. In certain embodiments, , wherein the S is attached to A ¹ . In certain embodiments E is a moiety formed by reacting two click-chemistry handles (eg two orthogonal click-chemistry handles). In certain embodiments, E is a single bond, –O–, –S–, – NR ^a –, –C(=O)O–, –C(=NR ^a )O–, –S(=O)O–, –S(=O)2O–, –C(=O)NR ^a –, –C(=NR ^a )NR ^a –, – S(=O)NR ^a –, –S(=O)2NR ^a –, –OC(=O)–, –OC(=NR ^a )–, –OS(=O)–, –OS(=O)2–, –NR ^a C(=O)–, – NR ^a C(=NR ^a )–, –NR ^a S(=O)–, –NR ^a S(=O) ₂ –, –OC(=O)O–, –OC(=NR ^a )O–, –OS(=O)O–, – OS(=O)2O–, –NR ^a C(=O)O–, –NR ^a C(=NR ^a )O–, –NR ^a S(=O)O–, –NR ^a S(=O)2O–, –OC(=O)NR ^a –, –OC(=NR ^a )NR ^a –, –OS(=O)NR ^a –, –OS(=O)2NR ^a –, –NR ^a C(=O)NR ^a –, –NR ^a C(=NR ^a )NR ^a –, – NR ^a S(=O)NR ^a –, –NR ^a S(=O) ₂ NR ^a –, –C(=O)–, –C(=NR ^a )–, –S(=O)–, or –S(=O) ₂ –. In certain In another aspect, the present disclosure provides a method of preparing a conjugate of Formula (IV’), or a tautomer, isotopically labeled conjugate, or salt thereof, the method comprising reacting the end-functionalized polymer with a biomolecule of Formula (C’): (C’), wherein: each instance of E ² is independently –SH, a second click-chemistry handle, an electrophile, a nucleophile, or a leaving group, H, halogen, substituted or unsubstituted, C _1-6 alkyl, substituted or unsubstituted, C _2-6 alkenyl, substituted or unsubstituted, C _2-6 alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, –OR ^a , –N(R ^a )2, –SR ^a , –CN, –SCN, – C(=O)R ^a , –C(=O)OR ^a , –C(=O)N(R ^a ) ₂ , –C(=NR ^a )R ^a , –C(=NR ^a )OR ^a , –C(=NR ^a )N(R ^a ) ₂ , –NO ₂ , – N3, –NR ^a C(=O)R ^a , –NR ^a C(=O)OR ^a , –NR ^a C(=O)N(R ^a )2, –NR ^a C(=NR ^a )R ^a , –NR ^a C(=NR ^a )OR ^a , – NR ^a C(=NR ^a )N(R ^a )2, –OC(=O)R ^a , –OC(=O)OR ^a , –OC(=O)N(R ^a )2, –OC(=NR ^a )R ^a , – OC(=NR ^a )OR ^a , –OC(=NR ^a )N(R ^a ) ₂ , –NR ^a S(=O) ₂ R ^a , –NR ^a S(=O) ₂ OR ^a , –NR ^a S(=O) ₂ N(R ^a ) ₂ , – OS(=O)R ^a , –OS(=O)OR ^a , –OS(=O)N(R ^a )2, –S(=O)R ^a , –S(=O)OR ^a , –S(=O)N(R ^a )2, –OS(=O)2R ^a , –OS(=O)2OR ^a , –OS(=O)2N(R ^a )2, –S(=O)2R ^a , –S(=O)2OR ^a , –S(=O)2N(R ^a )2, or –P(=O)(R ^a )2; n1 is an integer between 1 and 20, inclusive; A ¹ is a peptide, protein, nucleoprotein, mucoprotein, lipoprotein, glycoprotein, or polynucleotide; and each instance of E is independently a moiety formed by reacting under suitable conditions an instance of E ¹ with an instance of E ² . In certain embodiments, Formula (C’) is Formula (C): (E ² )n1–A ¹ (C). In certain embodiments, the suitable conditions are physiological conditions. Compositions, Kits, and Methods of Use In another aspect, the present disclosure provides a composition comprising the enyne, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, and optionally an excipient. In certain embodiments, the composition comprises an effective amount of the enyne, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co- crystal thereof. In another aspect, the present disclosure provides a composition comprising the end- functionalized polymer, or a tautomer, isotopically labeled polymer, or salt thereof, and optionally an excipient. In certain embodiments, the composition comprises an effective amount of the end-functionalized polymer, or a tautomer, isotopically labeled polymer, or salt thereof. In another aspect, the present disclosure provides a composition comprising the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof, and optionally an excipient. In certain embodiments, the composition comprises an effective amount of the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof. In certain embodiments, the composition is a pharmaceutical composition, wherein the excipient is a pharmaceutically acceptable excipient. In certain embodiments, the compositions are useful for delivering an agent (e.g., to a subject in need thereof or cell). In certain embodiments, the compositions are useful for treating a disease in a subject in need thereof. In certain embodiments, the compositions are useful for preventing a disease in a subject in need thereof. In certain embodiments, the compositions are useful for diagnosing a disease in a subject in need thereof. In certain embodiments, the subject is an animal. In certain embodiments, the subject is a mammal. In certain embodiments, the subject is a human. In certain embodiments, the subject is a human two-years and older. In certain embodiments, the subject is a human eighteen-years and older. In certain embodiments, the cell is in vitro. In certain embodiments, the cell is in vivo. Pharmaceutical compositions described herein can be prepared by any method known in the art of pharmacology. In general, such preparatory methods include bringing the conjugate described herein (which may includes a therapeutic agent (the “active ingredient”)) into association with a carrier or excipient, and/or one or more other accessory ingredients, and then, if necessary and/or desirable, shaping, and/or packaging the product into a desired single- or multi-dose unit. Pharmaceutical compositions can be prepared, packaged, and/or sold in bulk, as a single unit dose and/or as a plurality of single unit doses A “unit dose” is a discrete amount of the pharmaceutical composition comprising a predetermined amount of the active ingredient. The amount of the active ingredient is generally equal to the dosage of the active ingredient which would be administered to a subject and/or a convenient fraction of such a dosage, such as one- half or one-third of such a dosage. Relative amounts of the active ingredient, the pharmaceutically acceptable excipient, and/or any additional ingredients in a pharmaceutical composition described herein will vary, depending upon the identity, size, and/or condition of the subject treated and further depending upon the route by which the composition is to be administered. The composition may comprise between 0.1% and 100% (w/w) active ingredient. Pharmaceutically acceptable excipients used in the manufacture of provided pharmaceutical compositions include inert diluents, dispersing and/or granulating agents, surface active agents and/or emulsifiers, disintegrating agents, binding agents, preservatives, buffering agents, lubricating agents, and/or oils. Excipients such as cocoa butter and suppository waxes, coloring agents, coating agents, sweetening, flavoring, and perfuming agents may also be present in the composition. Exemplary diluents include calcium carbonate, sodium carbonate, calcium phosphate, dicalcium phosphate, calcium sulfate, calcium hydrogen phosphate, sodium phosphate lactose, sucrose, cellulose, microcrystalline cellulose, kaolin, mannitol, sorbitol, inositol, sodium chloride, dry starch, cornstarch, powdered sugar, and mixtures thereof. Exemplary granulating and/or dispersing agents include potato starch, corn starch, tapioca starch, sodium starch glycolate, clays, alginic acid, guar gum, citrus pulp, agar, bentonite, cellulose, and wood products, natural sponge, cation-exchange resins, calcium carbonate, silicates, sodium carbonate, cross-linked poly(vinyl-pyrrolidone) (crospovidone), sodium carboxymethyl starch (sodium starch glycolate), carboxymethyl cellulose, cross-linked sodium carboxymethyl cellulose (croscarmellose), methylcellulose, pregelatinized starch (starch 1500), microcrystalline starch, water insoluble starch, calcium carboxymethyl cellulose, magnesium aluminum silicate (Veegum), sodium lauryl sulfate, quaternary ammonium compounds, and mixtures thereof. Exemplary surface active agents and/or emulsifiers include natural emulsifiers (e.g., acacia, agar, alginic acid, sodium alginate, tragacanth, chondrux, cholesterol, xanthan, pectin, gelatin, egg yolk, casein, wool fat, cholesterol, wax, and lecithin), colloidal clays (e.g., bentonite (aluminum silicate) and Veegum (magnesium aluminum silicate)), long chain amino acid derivatives, high molecular weight alcohols (e.g., stearyl alcohol, cetyl alcohol, oleyl alcohol, triacetin monostearate, ethylene glycol distearate, glyceryl monostearate, and propylene glycol monostearate polyvinyl alcohol) carbomers (eg carboxy polymethylene polyacrylic acid acrylic acid polymer, and carboxyvinyl polymer), carrageenan, cellulosic derivatives (e.g., carboxymethylcellulose sodium, powdered cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, methylcellulose), sorbitan fatty acid esters (e.g., polyoxyethylene sorbitan monolaurate (Tween ^® 20), polyoxyethylene sorbitan monostearate (Tween ^® 60), polyoxyethylene sorbitan monooleate (Tween ^® 80), sorbitan monopalmitate (Span ^® 40), sorbitan monostearate (Span ^® 60), sorbitan tristearate (Span ^® 65), glyceryl monooleate, sorbitan monooleate (Span ^® 80), polyoxyethylene esters (e.g., polyoxyethylene monostearate (Myrj ^® 45), polyoxyethylene hydrogenated castor oil, polyethoxylated castor oil, polyoxymethylene stearate, and Solutol ^® ), sucrose fatty acid esters, polyethylene glycol fatty acid esters (e.g., Cremophor ^® ), polyoxyethylene ethers, (e.g., polyoxyethylene lauryl ether (Brij ^® 30)), poly(vinyl-pyrrolidone), diethylene glycol monolaurate, triethanolamine oleate, sodium oleate, potassium oleate, ethyl oleate, oleic acid, ethyl laurate, sodium lauryl sulfate, Pluronic ^® F-68, poloxamer P-188, cetrimonium bromide, cetylpyridinium chloride, benzalkonium chloride, docusate sodium, and/or mixtures thereof. Exemplary binding agents include starch (e.g., cornstarch and starch paste), gelatin, sugars (e.g., sucrose, glucose, dextrose, dextrin, molasses, lactose, lactitol, mannitol, etc.), natural and synthetic gums (e.g., acacia, sodium alginate, extract of Irish moss, panwar gum, ghatti gum, mucilage of isapol husks, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose, microcrystalline cellulose, cellulose acetate, poly(vinyl-pyrrolidone), magnesium aluminum silicate (Veegum ^® ), and larch arabogalactan), alginates, polyethylene oxide, polyethylene glycol, inorganic calcium salts, silicic acid, polymethacrylates, waxes, water, alcohol, and/or mixtures thereof. Exemplary preservatives include antioxidants, chelating agents, antimicrobial preservatives, antifungal preservatives, antiprotozoan preservatives, alcohol preservatives, acidic preservatives, and other preservatives. In certain embodiments, the preservative is an antioxidant. In other embodiments, the preservative is a chelating agent. Exemplary antioxidants include alpha tocopherol, ascorbic acid, acorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, monothioglycerol, potassium metabisulfite, propionic acid, propyl gallate, sodium ascorbate, sodium bisulfite, sodium metabisulfite, and sodium sulfite. Exemplary chelating agents include ethylenediaminetetraacetic acid (EDTA) and salts and hydrates thereof (e.g., sodium edetate, disodium edetate, trisodium edetate, calcium disodium edetate, dipotassium edetate, and the like), citric acid and salts and hydrates thereof (e.g., citric acid monohydrate) fumaric acid and salts and hydrates thereof malic acid and salts and hydrates thereof, phosphoric acid and salts and hydrates thereof, and tartaric acid and salts and hydrates thereof. Exemplary antimicrobial preservatives include benzalkonium chloride, benzethonium chloride, benzyl alcohol, bronopol, cetrimide, cetylpyridinium chloride, chlorhexidine, chlorobutanol, chlorocresol, chloroxylenol, cresol, ethyl alcohol, glycerin, hexetidine, imidurea, phenol, phenoxyethanol, phenylethyl alcohol, phenylmercuric nitrate, propylene glycol, and thimerosal. Exemplary antifungal preservatives include butyl paraben, methyl paraben, ethyl paraben, propyl paraben, benzoic acid, hydroxybenzoic acid, potassium benzoate, potassium sorbate, sodium benzoate, sodium propionate, and sorbic acid. Exemplary alcohol preservatives include ethanol, polyethylene glycol, phenol, phenolic compounds, bisphenol, chlorobutanol, hydroxybenzoate, and phenylethyl alcohol. Exemplary acidic preservatives include vitamin A, vitamin C, vitamin E, beta-carotene, citric acid, acetic acid, dehydroacetic acid, ascorbic acid, sorbic acid, and phytic acid. Other preservatives include tocopherol, tocopherol acetate, deteroxime mesylate, cetrimide, butylated hydroxyanisol (BHA), butylated hydroxytoluened (BHT), ethylenediamine, sodium lauryl sulfate (SLS), sodium lauryl ether sulfate (SLES), sodium bisulfite, sodium metabisulfite, potassium sulfite, potassium metabisulfite, Glydant ^® Plus, Phenonip ^® , methylparaben, Germall ^® 115, Germaben ^® II, Neolone ^® , Kathon ^® , and Euxyl ^® . Exemplary buffering agents include citrate buffer solutions, acetate buffer solutions, phosphate buffer solutions, ammonium chloride, calcium carbonate, calcium chloride, calcium citrate, calcium glubionate, calcium gluceptate, calcium gluconate, D-gluconic acid, calcium glycerophosphate, calcium lactate, propanoic acid, calcium levulinate, pentanoic acid, dibasic calcium phosphate, phosphoric acid, tribasic calcium phosphate, calcium hydroxide phosphate, potassium acetate, potassium chloride, potassium gluconate, potassium mixtures, dibasic potassium phosphate, monobasic potassium phosphate, potassium phosphate mixtures, sodium acetate, sodium bicarbonate, sodium chloride, sodium citrate, sodium lactate, dibasic sodium phosphate, monobasic sodium phosphate, sodium phosphate mixtures, tromethamine, magnesium hydroxide, aluminum hydroxide, alginic acid, pyrogen-free water, isotonic saline, Ringer’s solution, ethyl alcohol, and mixtures thereof. Exemplary lubricating agents include magnesium stearate, calcium stearate, stearic acid, silica, talc, malt, glyceryl behanate, hydrogenated vegetable oils, polyethylene glycol, sodium benzoate, sodium acetate, sodium chloride, leucine, magnesium lauryl sulfate, sodium lauryl sulfate, and mixtures thereof. Exemplary natural oils include almond, apricot kernel, avocado, babassu, bergamot, black current seed borage cade camomile canola caraway carnauba castor cinnamon cocoa butter, coconut, cod liver, coffee, corn, cotton seed, emu, eucalyptus, evening primrose, fish, flaxseed, geraniol, gourd, grape seed, hazel nut, hyssop, isopropyl myristate, jojoba, kukui nut, lavandin, lavender, lemon, litsea cubeba, macademia nut, mallow, mango seed, meadowfoam seed, mink, nutmeg, olive, orange, orange roughy, palm, palm kernel, peach kernel, peanut, poppy seed, pumpkin seed, rapeseed, rice bran, rosemary, safflower, sandalwood, sasquana, savoury, sea buckthorn, sesame, shea butter, silicone, soybean, sunflower, tea tree, thistle, tsubaki, vetiver, walnut, and wheat germ oils. Exemplary synthetic oils include butyl stearate, caprylic triglyceride, capric triglyceride, cyclomethicone, diethyl sebacate, dimethicone 360, isopropyl myristate, mineral oil, octyldodecanol, oleyl alcohol, silicone oil, and mixtures thereof. Liquid dosage forms for oral and parenteral administration include pharmaceutically acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. In addition to the active ingredients, the liquid dosage forms may comprise inert diluents commonly used in the art such as, for example, water or other solvents, solubilizing agents and emulsifiers such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, dimethylformamide, oils (e.g., cottonseed, groundnut, corn, germ, olive, castor, and sesame oils), glycerol, tetrahydrofurfuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan, and mixtures thereof. Besides inert diluents, the oral compositions can include adjuvants such as wetting agents, emulsifying and suspending agents, sweetening, flavoring, and perfuming agents. In certain embodiments for parenteral administration, the conjugates described herein are mixed with solubilizing agents such as Cremophor ^® , alcohols, oils, modified oils, glycols, polysorbates, cyclodextrins, polymers, and mixtures thereof. Injectable preparations, for example, sterile injectable aqueous or oleaginous suspensions can be formulated according to the known art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparation can be a sterile injectable solution, suspension, or emulsion in a nontoxic parenterally acceptable diluent or solvent, for example, as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that can be employed are water, Ringer’s solution, U.S.P., and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil can be employed including synthetic mono- or di-glycerides. In addition, fatty acids such as oleic acid are used in the preparation of injectables. The injectable formulations can be sterilized, for example, by filtration through a bacterial-retaining filter, or by incorporating sterilizing agents in the form of sterile solid compositions which can be dissolved or dispersed in sterile water or other sterile injectable medium prior to use In order to prolong the effect of a drug, it is often desirable to slow the absorption of the drug from subcutaneous or intramuscular injection. This can be accomplished by the use of a liquid suspension of crystalline or amorphous material with poor water solubility. The rate of absorption of the drug then depends upon its rate of dissolution, which, in turn, may depend upon crystal size and crystalline form. Alternatively, delayed absorption of a parenterally administered drug form may be accomplished by dissolving or suspending the drug in an oil vehicle. Compositions for rectal or vaginal administration are typically suppositories which can be prepared by mixing the conjugates described herein with suitable non-irritating excipients or carriers such as cocoa butter, polyethylene glycol, or a suppository wax which are solid at ambient temperature but liquid at body temperature and therefore melt in the rectum or vaginal cavity and release the active ingredient. Solid dosage forms for oral administration include capsules, tablets, pills, powders, and granules. In such solid dosage forms, the active ingredient is mixed with at least one inert, pharmaceutically acceptable excipient or carrier such as sodium citrate or dicalcium phosphate and/or (a) fillers or extenders such as starches, lactose, sucrose, glucose, mannitol, and silicic acid, (b) binders such as, for example, carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidinone, sucrose, and acacia, (c) humectants such as glycerol, (d) disintegrating agents such as agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and sodium carbonate, (e) solution retarding agents such as paraffin, (f) absorption accelerators such as quaternary ammonium compounds, (g) wetting agents such as, for example, cetyl alcohol and glycerol monostearate, (h) absorbents such as kaolin and bentonite clay, and (i) lubricants such as talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, and mixtures thereof. In the case of capsules, tablets, and pills, the dosage form may include a buffering agent. Solid compositions of a similar type can be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugar as well as high molecular weight polyethylene glycols and the like. The solid dosage forms of tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells such as enteric coatings and other coatings well known in the art of pharmacology. They may optionally comprise opacifying agents and can be of a composition that they release the active ingredient(s) only, or preferentially, in a certain part of the intestinal tract, optionally, in a delayed manner. Examples of encapsulating compositions which can be used include polymeric substances and waxes. Solid compositions of a similar type can be employed as fillers in soft and hard-filled gelatin capsules using such excipients as lactose or milk sugar as well as high molecular weight polethylene glycols and the like. The active ingredient can be in a micro-encapsulated form with one or more excipients as noted above. The solid dosage forms of tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells such as enteric coatings, release controlling coatings, and other coatings well known in the pharmaceutical formulating art. In such solid dosage forms the active ingredient can be admixed with at least one inert diluent such as sucrose, lactose, or starch. Such dosage forms may comprise, as is normal practice, additional substances other than inert diluents, e.g., tableting lubricants and other tableting aids such a magnesium stearate and microcrystalline cellulose. In the case of capsules, tablets and pills, the dosage forms may comprise buffering agents. They may optionally comprise opacifying agents and can be of a composition that they release the active ingredient(s) only, or preferentially, in a certain part of the intestinal tract, optionally, in a delayed manner. Examples of encapsulating agents which can be used include polymeric substances and waxes. Dosage forms for topical and/or transdermal administration of a conjugate described herein may include ointments, pastes, creams, lotions, gels, powders, solutions, sprays, inhalants, and/or patches. Generally, the active ingredient is admixed under sterile conditions with a pharmaceutically acceptable carrier or excipient and/or any needed preservatives and/or buffers as can be required. Additionally, the present disclosure contemplates the use of transdermal patches, which often have the added advantage of providing controlled delivery of an active ingredient to the body. Such dosage forms can be prepared, for example, by dissolving and/or dispensing the active ingredient in the proper medium. Alternatively or additionally, the rate can be controlled by either providing a rate controlling membrane and/or by dispersing the active ingredient in a polymer matrix and/or gel. Suitable devices for use in delivering intradermal pharmaceutical compositions described herein include short needle devices. Intradermal compositions can be administered by devices which limit the effective penetration length of a needle into the skin. Alternatively or additionally, conventional syringes can be used in the classical mantoux method of intradermal administration. Jet injection devices which deliver liquid formulations to the dermis via a liquid jet injector and/or via a needle which pierces the stratum corneum and produces a jet which reaches the dermis are suitable. Ballistic powder/particle delivery devices which use compressed gas to accelerate the conjugate in powder form through the outer layers of the skin to the dermis are suitable. Formulations suitable for topical administration include liquid and/or semi-liquid preparations such as liniments, lotions, oil-in-water and/or water-in-oil emulsions such as creams, ointments, and/or pastes, and/or solutions and/or suspensions. Topically administrable formulations may for example comprise from about 1% to about 10% (w/w) active ingredient although the concentration of the active ingredient can be as high as the solubility limit of the active ingredient in the solvent. Formulations for topical administration may further comprise one or more of the additional ingredients described herein. A pharmaceutical composition described herein can be prepared, packaged, and/or sold in a formulation suitable for pulmonary administration via the buccal cavity. Such a formulation may comprise dry particles which comprise the active ingredient and which have a diameter in the range from about 0.5 to about 7 nanometers, or from about 1 to about 6 nanometers. Such compositions are conveniently in the form of dry powders for administration using a device comprising a dry powder reservoir to which a stream of propellant can be directed to disperse the powder and/or using a self-propelling solvent/powder dispensing container such as a device comprising the active ingredient dissolved and/or suspended in a low-boiling propellant in a sealed container. Such powders comprise particles wherein at least 98% of the particles by weight have a diameter greater than 0.5 nanometers and at least 95% of the particles by number have a diameter less than 7 nanometers. Alternatively, at least 95% of the particles by weight have a diameter greater than 1 nanometer and at least 90% of the particles by number have a diameter less than 6 nanometers. Dry powder compositions may include a solid fine powder diluent such as sugar and are conveniently provided in a unit dose form. Low boiling propellants generally include liquid propellants having a boiling point of below 65 °F at atmospheric pressure. Generally the propellant may constitute 50 to 99.9% (w/w) of the composition, and the active ingredient may constitute 0.1 to 20% (w/w) of the composition. The propellant may further comprise additional ingredients such as a liquid non- ionic and/or solid anionic surfactant and/or a solid diluent (which may have a particle size of the same order as particles comprising the active ingredient). Pharmaceutical compositions described herein formulated for pulmonary delivery may provide the active ingredient in the form of droplets of a solution and/or suspension. Such formulations can be prepared, packaged, and/or sold as aqueous and/or dilute alcoholic solutions and/or suspensions, optionally sterile, comprising the active ingredient, and may conveniently be administered using any nebulization and/or atomization device. Such formulations may further comprise one or more additional ingredients including a flavoring agent such as saccharin sodium, a volatile oil, a buffering agent, a surface active agent, and/or a preservative such as methylhydroxybenzoate. The droplets provided by this route of administration may have an average diameter in the range from about 0.1 to about 200 nanometers. Formulations described herein as being useful for pulmonary delivery are useful for intranasal delivery of a pharmaceutical composition described herein. Another formulation suitable for intranasal administration is a coarse powder comprising the active ingredient and having an average particle from about 0.2 to 500 micrometers. Such a formulation is administered by rapid inhalation through the nasal passage from a container of the powder held close to the nares. Formulations for nasal administration may, for example, comprise from about as little as 0.1% (w/w) to as much as 100% (w/w) of the active ingredient, and may comprise one or more of the additional ingredients described herein. A pharmaceutical composition described herein can be prepared, packaged, and/or sold in a formulation for buccal administration. Such formulations may, for example, be in the form of tablets and/or lozenges made using conventional methods, and may contain, for example, 0.1 to 20% (w/w) active ingredient, the balance comprising an orally dissolvable and/or degradable composition and, optionally, one or more of the additional ingredients described herein. Alternately, formulations for buccal administration may comprise a powder and/or an aerosolized and/or atomized solution and/or suspension comprising the active ingredient. Such powdered, aerosolized, and/or aerosolized formulations, when dispersed, may have an average particle and/or droplet size in the range from about 0.1 to about 200 nanometers, and may further comprise one or more of the additional ingredients described herein. A pharmaceutical composition described herein can be prepared, packaged, and/or sold in a formulation for ophthalmic administration. Such formulations may, for example, be in the form of eye drops including, for example, a 0.1-1.0% (w/w) solution and/or suspension of the active ingredient in an aqueous or oily liquid carrier or excipient. Such drops may further comprise buffering agents, salts, and/or one or more other of the additional ingredients described herein. Other opthalmically-administrable formulations which are useful include those which comprise the active ingredient in microcrystalline form and/or in a liposomal preparation. Ear drops and/or eye drops are also contemplated as being within the scope of this disclosure. Although the descriptions of pharmaceutical compositions provided herein are principally directed to pharmaceutical compositions which are suitable for administration to humans, it will be understood by the skilled artisan that such compositions are generally suitable for administration to animals of all sorts. Modification of pharmaceutical compositions suitable for administration to humans in order to render the compositions suitable for administration to various animals is well understood, and the ordinarily skilled veterinary pharmacologist can design and/or perform such modification with ordinary experimentation. Polymers provided herein are typically formulated in dosage unit form for ease of administration and uniformity of dosage. It will be understood, however, that the total daily usage of the compositions described herein will be decided by a physician within the scope of sound medical judgment. The specific therapeutically effective dose level for any particular subject or organism will depend upon a variety of factors including the disease being treated and the severity of the disorder; the activity of the specific active ingredient employed; the specific composition employed; the age, body weight, general health, sex, and diet of the subject; the time of administration, route of administration, and rate of excretion of the specific active ingredient employed; the duration of the treatment; drugs used in combination or coincidental with the specific active ingredient employed; and like factors well known in the medical arts. The conjugates and compositions provided herein can be administered by any route, including enteral (e.g., oral), parenteral, intravenous, intramuscular, intra-arterial, intramedullary, intrathecal, subcutaneous, intraventricular, transdermal, interdermal, rectal, intravaginal, intraperitoneal, topical (as by powders, ointments, creams, and/or drops), mucosal, nasal, bucal, sublingual; by intratracheal instillation, bronchial instillation, and/or inhalation; and/or as an oral spray, nasal spray, and/or aerosol. Specifically contemplated routes are oral administration, intravenous administration (e.g., systemic intravenous injection), regional administration via blood and/or lymph supply, and/or direct administration to an affected site. In general, the most appropriate route of administration will depend upon a variety of factors including the nature of the agent (e.g., its stability in the environment of the gastrointestinal tract), and/or the condition of the subject (e.g., whether the subject is able to tolerate oral administration). In certain embodiments, the conjugate or pharmaceutical composition described herein is suitable for topical administration to the eye of a subject. The exact amount of a conjugate required to achieve an effective amount will vary from subject to subject, depending, for example, on species, age, and general condition of a subject, severity of the side effects or disorder, identity of the particular conjugate, mode of administration, and the like. An effective amount may be included in a single dose (e.g., single oral dose) or multiple doses (e.g., multiple oral doses). In certain embodiments, when multiple doses are administered to a subject or applied to a tissue or cell, any two doses of the multiple doses include different or substantially the same amounts of a conjugate described herein. In certain embodiments, when multiple doses are administered to a subject or applied to a tissue or cell, the frequency of administering the multiple doses to the subject or applying the multiple doses to the tissue or cell is three doses a day, two doses a day, one dose a day, one dose every other day, one dose every third day, one dose every week, one dose every two weeks, one dose every three weeks, or one dose every four weeks. In certain embodiments, the frequency of administering the multiple doses to the subject or applying the multiple doses to the tissue or cell is one dose per day. In certain embodiments, the frequency of administering the multiple doses to the subject or applying the multiple doses to the tissue or cell is two doses per day. In certain embodiments, the frequency of administering the multiple doses to the subject or applying the multiple doses to the tissue or cell is three doses per day In certain embodiments when multiple doses are administered to a subject or applied to a tissue or cell, the duration between the first dose and last dose of the multiple doses is one day, two days, four days, one week, two weeks, three weeks, one month, two months, three months, four months, six months, nine months, one year, two years, three years, four years, five years, seven years, ten years, fifteen years, twenty years, or the lifetime of the subject, tissue, or cell. In certain embodiments, the duration between the first dose and last dose of the multiple doses is three months, six months, or one year. In certain embodiments, the duration between the first dose and last dose of the multiple doses is the lifetime of the subject, tissue, or cell. In certain embodiments, a dose (e.g., a single dose, or any dose of multiple doses) described herein includes independently between 0.1 µg and 1 µg, between 0.001 mg and 0.01 mg, between 0.01 mg and 0.1 mg, between 0.1 mg and 1 mg, between 1 mg and 3 mg, between 3 mg and 10 mg, between 10 mg and 30 mg, between 30 mg and 100 mg, between 100 mg and 300 mg, between 300 mg and 1,000 mg, or between 1 g and 10 g, inclusive, of a conjugate described herein. In certain embodiments, a dose described herein includes independently between 1 mg and 3 mg, inclusive, of a conjugate described herein. In certain embodiments, a dose described herein includes independently between 3 mg and 10 mg, inclusive, of a conjugate described herein. In certain embodiments, a dose described herein includes independently between 10 mg and 30 mg, inclusive, of a conjugate described herein. In certain embodiments, a dose described herein includes independently between 30 mg and 100 mg, inclusive, of a conjugate described herein. Dose ranges as described herein provide guidance for the administration of provided pharmaceutical compositions to an adult. The amount to be administered to, for example, a child or an adolescent can be determined by a medical practitioner or person skilled in the art and can be lower or the same as that administered to an adult. In certain embodiments, a dose described herein is a dose to an adult human whose body weight is 70 kg. The conjugate or composition can be administered in combination with one or more additional pharmaceutical agents (e.g., therapeutically and/or prophylactically active agents). The conjugate or composition can be administered in combination with additional pharmaceutical agents that improve their activity (e.g., activity (e.g., potency and/or efficacy) in treating a disease in a subject in need thereof, in preventing a disease in a subject in need thereof, in reducing the risk to develop a disease in a subject in need thereof, and/or in inhibiting the activity of a protein kinase in a subject or cell), improve bioavailability, improve safety, reduce drug resistance, reduce and/or modify metabolism, inhibit excretion, and/or modify distribution in a subject or cell. It will also be appreciated that the therapy employed may achieve a desired effect for the same disorder, and/or it may achieve different effects. In certain embodiments, a pharmaceutical composition described herein including a conjugate described herein and an additional pharmaceutical agent shows a synergistic effect that is absent in a pharmaceutical composition including one of the polymer/ conjugate and the additional pharmaceutical agent, but not both. The conjugate or composition can be administered concurrently with, prior to, or subsequent to one or more additional pharmaceutical agents, which are different from the conjugate or composition and may be useful as, e.g., combination therapies. Pharmaceutical agents include therapeutically active agents. Pharmaceutical agents also include prophylactically active agents. Pharmaceutical agents include small organic molecules such as drug compounds (e.g., compounds approved for human or veterinary use by the U.S. Food and Drug Administration as provided in the Code of Federal Regulations (CFR)), peptides, proteins, carbohydrates, monosaccharides, oligosaccharides, polysaccharides, nucleoproteins, mucoproteins, lipoproteins, synthetic polypeptides or proteins, small molecules linked to proteins, glycoproteins, steroids, nucleic acids, DNAs, RNAs, nucleotides, nucleosides, oligonucleotides, antisense oligonucleotides, lipids, hormones, vitamins, and cells. In certain embodiments, the additional pharmaceutical agent is a pharmaceutical agent useful for treating and/or preventing a disease (e.g., proliferative disease, hematological disease, neurological disease, painful condition, psychiatric disorder, or metabolic disorder). Each additional pharmaceutical agent may be administered at a dose and/or on a time schedule determined for that pharmaceutical agent. The additional pharmaceutical agents may also be administered together with each other and/or with the conjugate or composition described herein in a single dose or administered separately in different doses. The particular combination to employ in a regimen will take into account compatibility of the conjugate described herein with the additional pharmaceutical agent(s) and/or the desired therapeutic and/or prophylactic effect to be achieved. In general, it is expected that the additional pharmaceutical agent(s) in combination be utilized at levels that do not exceed the levels at which they are utilized individually. In some embodiments, the levels utilized in combination will be lower than those utilized individually. The additional pharmaceutical agents include anti-proliferative agents, anti-cancer agents, cytotoxic agents, anti-angiogenesis agents, anti-inflammatory agents, immunosuppressants, anti- bacterial agents, anti-viral agents, cardiovascular agents, cholesterol-lowering agents, anti- diabetic agents, anti-allergic agents, contraceptive agents, and pain-relieving agents. In certain embodiments, the additional pharmaceutical agent is an anti-proliferative agent. In certain embodiments, the additional pharmaceutical agent is an anti-cancer agent. In certain embodiments, the additional pharmaceutical agent is an anti-viral agent. In certain embodiments, the additional pharmaceutical agent is a binder or inhibitor of a protein kinase. In certain embodiments the additional pharmaceutical agent is selected from the group consisting of epigenetic or transcriptional modulators (e.g., DNA methyltransferase inhibitors, histone deacetylase inhibitors (HDAC inhibitors), lysine methyltransferase inhibitors), antimitotic drugs (e.g., taxanes and vinca alkaloids), hormone receptor modulators (e.g., estrogen receptor modulators and androgen receptor modulators), cell signaling pathway inhibitors (e.g., tyrosine protein kinase inhibitors), modulators of protein stability (e.g., proteasome inhibitors), Hsp90 inhibitors, glucocorticoids, all-trans retinoic acids, and other agents that promote differentiation. In certain embodiments, the conjugate described herein or pharmaceutical composition can be administered in combination with an anti-cancer therapy including surgery, radiation therapy, transplantation (e.g., stem cell transplantation, bone marrow transplantation), immunotherapy, and chemotherapy. In some embodiments, the percentage of the conjugates (e.g., in a particle) that comprise an agent is between about 1 and about 100% (e.g., about 1%, about 2%, about 3%, about 4%, about 5%, about 10%, about 15%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, or about 100%). In some embodiments, the percentage of the conjugates that comprise an agent is less than about 50%, e.g., less than about 40%, less than about 35%, less than about 30%, less than about 25%, less than about 20%, less than about 15%, or less than about 10%. In some embodiments, the percentage of the conjugates (e.g., in a particle) that comprise an agent is between about 5% and about 50%, about 5% and about 40%, about 5% and about 30%, about 5% and about 25%, or about 5% and about 20%. In some embodiments, the percentage of the conjugates (e.g., in a particle) that comprise an agent is between about 5% and 90%. In some embodiments, the percentage of the conjugates (e.g., in a particle) that comprise an agent is between about 5% and about 75%. In the some embodiments, the the conjugates (e.g., in a particle) that comprise an agent is between about 5% and about 50%. In the some embodiments, the percentage of the conjugates (e.g., in a particle) that comprise an agent is between about 10% and about 25%. In some embodiments, the total amount of the agent present in the Brush prodrug or particle is greater than about 5% (e.g., about 6%, about 7%, about 8%, about 9%, about 10%, about 12%, about 15%, about 20%, about 25%, about 30%, or more) of the total size or weight of the Brush prodrug or particle. In some embodiments, the total amount of the agent present in the Brush prodrug or particle is greater than about 10% (e.g., about 12%, about 15%, about 20%, about 25%, about 30%, or more) of the total size or weight of the Brush prodrug or particle. Without being bound by theory, the conugates or particles disclosed herein may improve the efficiency of an agent by one or more of increasing the localization and/or release (e.g., preferential release) of the agent to a target cell (e.g., a cancer or a fibrotic cell; a cell associated with a hypoxic environment) or increasing the half life of the agent thus resulting in a significantly higher amount of a released agent at a target site (e.g., a tumor or liver (e.g., cirrhotic cell). According, the conjugates and particles disclosed herein can be more effective therapeutically than the free agent (e.g., due to enhanced drug uptake in the target tissue) and/or allow for a lower therapeutic dose of the agent, e.g., without substantially compromising the resulting drug concentration at a target tissue. In some embodiments, the conjugates and particles disclosed herein can reduce the adverse effect associated with systemic administration of an agent in free form (e.g., not coupled to a conjugate or particle described herein). Without being bound by theory, due to the localized delivery of the compositions described herein (e.g., the agent-containing particles), a lower dose or amount of the agent in the particles can be administered (e.g., through local sustained delivery) compared to the agent in free form. In other embodiments, the agent-containing particles are administered at a dose or amount of the agent that is less than the dose or amount of said agent in free form to have a desired effect (e.g., a desired therapeutic effect). In some embodiments, the agent is incorporated into a particle at a dose that is less than the dose or amount of said agent in free form to have a desired effect (e.g., a desired therapeutic effect), e.g., the standard of care dose for the intended use of the free agent. In one embodiment, the agent are incorporated into the particles at a dose or amount of the agent that is less than the standard of care dose of the agent for a desired therapy (e.g., a dose that is less than about 0.01, about 0.02, about 0.03, about 0.04, about 0.05, about 0.06, about 0.07, about 0.08, about 0.09, about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, or about 0.95 that of the standard of care dose of the agent). In some embodiments, the agent is incorporated into a particle at a dose equivalent to the dose or amount of said agent in free form to have a desired effect (e.g., a desired therapeutic effect), e.g., the standard of care dose for the intended use of the free agent. In these embodiments, the particle produces a greater therapeutic effect and/or a less adverse effect than the free agent. In certain embodiments, the particle increases the amount of the agent delivered to a tissue or cell in need thereof and reduces the amount of the agent exposed to a non-target tissue or cell, as compared to the free agent. In some embodiments, the agent is incorporated into a particle at a dose higher than the dose or amount of said agent in free form to have a desired effect (e.g., a desired therapeutic effect), e.g., the standard of care dose for the intended use of the free agent. In some embodiments, the agent is incorporated into a particle at a dose higher than the dose or amount of said agent in free form that would produce an adverse effect by systemic administration (e.g., a reduction in blood pressure). In some embodiments, since the particle described herein releases the agent at a target site based on pH microenvironment other non target sites (eg blood vessels) with different pH would be less likely to be exposed to the agent. In another aspect, the present disclosure provides a kit comprising: the enyne, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co- crystal thereof, or the composition; and instructions for using the enyne, tautomer, isotopically labeled compound, salt, solvate, polymorph, co-crystal, or composition. In another aspect, the present disclosure provides a kit comprising: the end-functionalized polymer, or a tautomer, isotopically labeled polymer, or salt thereof, or the composition; and instructions for using the end-functionalized polymer, tautomer, isotopically labeled polymer, salt, or composition. In another aspect, the present disclosure provides a kit comprising: the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof, or the composition; and instructions for using the conjugate, tautomer, isotopically labeled conjugate, salt, or composition. In certain embodiments, the kit comprises a first container. In certain embodiments, the first container comprises the enyne, or a tautomer, isotopically labeled compound, salt, solvate, polymorph, or co-crystal thereof, or the composition. In certain embodiments, the first container comprises the end-functionalized polymer, or a tautomer, isotopically labeled polymer, or salt thereof, or the composition. In certain embodiments, the first container comprises the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof, or the composition. In some embodiments, the kit further comprises a second container. In certain embodiments, the second container comprises the instructions. In certain embodiments, the instructions comprise information required by a regulatory agency, such as the U.S. Food and Drug Administration (FDA) or European Medicines Agency (EMA). In certain embodiments, the instructions comprise prescribing information. In certain embodiments, the second container comprises the first container. In some embodiments, the kit further comprises a third container. In certain embodiments, the third container comprises the excipient. In certain embodiments, the third container comprises the additional pharmaceutical agent. In certain embodiments, the second container comprises the third container. In certain embodiments, each of the first, second, and third containers is independently a vial, ampule, bottle, syringe, dispenser package, tube, or box. In another aspect, the present disclosure provides a method of delivering a pharmaceutical agent to a subject in need thereof comprising administering to the subject in need thereof: an effective amount of the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof; or the composition . In another aspect, the present disclosure provides a method of delivering a pharmaceutical agent to a cell comprising contacting the cell with an effective amount of: the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof; or the composition. In another aspect, the present disclosure provides a method of treating a disease in a subject in need thereof comprising administering to or implanting in the subject in need thereof an effective amount of: the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof; or the composition; wherein at least one pharmaceutical agent is a therapeutic agent. In another aspect, the present disclosure provides a method of preventing a disease in a subject in need thereof comprising administering to or implanting in the subject in need thereof a prophylactically effective amount of: the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof; or the composition; wherein at least one pharmaceutical agent is a prophylactic agent. In another aspect, the present disclosure provides a method of diagnosing a disease in a subject comprising administering to or implanting in the subject a diagnostically effective amount of: the conjugate, or a tautomer, isotopically labeled conjugate, or salt thereof; or the composition; wherein at least one pharmaceutical agent is a diagnostic agent. In certain embodiments, the disease is cancer, benign neoplasm, pathologic angiogenesis, inflammatory disease, autoinflammatory disease, autoimmune disease, metabolic disease, neurological disease, painful condition, or psychiatric disease. In certain embodiments, the disease is cancer. In certain embodiments, the disease is a hematological malignancy. In certain embodiments, the disease is lymphoma or leukemia. In certain embodiments, the disease is a solid tumor. In certain embodiments, the disease is bladder cancer, breast cancer, colon cancer, esophageal cancer, glioma, lung cancer, melanoma, multiple myeloma, Kaposi’s sarcoma, ovarian cancer, pancreatic cancer, prostate cancer, stomach cancer, soft tissue sarcoma, or thyroid cancer. In certain embodiments, the disease is breast cancer or ovarian cancer. In certain embodiments, the method of treating a disease further comprises administering to or implanting in the subject in need thereof an effective amount of an additional therapeutic agent In certain embodiments the method of preventing a disease further comprises administering to or implanting in the subject in need thereof an effective amount of an additional prophylactic agent. In certain embodiments, the method of diagnosing a disease further comprises administering to or implanting in the subject in need thereof an effective amount of an additional diagnostic agent. In certain embodiments, the additional therapeutic agent is an anti-cancer agent. EXAMPLES In order that the present disclosure may be more fully understood, the following examples are set forth. The synthetic and biological examples described in this application are offered to illustrate the compounds, pharmaceutical compositions, and methods provided herein and are not to be construed in any way as limiting their scope. Unless expressly provided otherwise, BPD is a brush polymer without antibody conjugation; ctrl-ABC is an ABC with IgG1 antibody conjugation; the anti-HER2 antibody is trastuzumab; ABC_Blank is an ABC without pharmaceutical agent conjugation; the general method suggested in FIG.17E was used to synthesize the anti-HER2 ABCs and the PROTAC- ABC; and MMAE-M was used to synthesize MMAE ABCs. Example 1. Synthesis of Antibody-Brush Polymer Conjugations Antibody-brush polymer conjugates (ABCs) were prepared via click reaction between a brush polymer and antibody (FIGs.17A to 17E). Synthesis of tetrazine terminated brush polymers Tetrazine terminated brush polymers were synthesized using the reaction shown in FIG. 17E, top panel. GPC traces showed the successful polymerization of brush polymers (FIGs.1 to 2). Synthesis of drug loaded brush polymers Drug loaded brush polymers were synthesized by polymerizing MMAE-S-MM (FIG.26), MMAE-M-MM (FIG.26), MMAE-F-MM (FIG.26), PTX-MM (FIG.27), DOX-MM (FIG.27), or SN-38-MM (FIG.27). MMAE: monomethyl auristatin E. PTX: paclitaxel. DOX: doxorubicin. SN-38: (4S)-4,11-diethyl-4,9-dihydroxy-1,4-dihydro-3H,14H-pyrano[3� ��,4′:6,7]indolizino[1,2- b]quinoline-3,14-dione. GPC traces showed the successful polymerization of drug conjugated brush polymers (FIGs.3A to 3B). Antibody lysine modification The surface of the antibody IgG was modified by trans-cyclooctene (TCO) moiety using the reaction shown in FIG.4A. Mass spectrometry analysis was performed for IgG (FIG.4B), NHS small molecule with PEG12 (PEG12) (FIG.4C) and NHS small molecule with PEG8 (PEG8) (FIG.4D). Azide-DBCO conjugation Polymers P1, P2, P3 and *P4 (control) were conjugated with IgG1:1:5 linker reaction (1 mg scale, 1mL); IgG2: 1:10 linker reaction (1 mg scale, 1 mL); IgG3: 1:15 linker reaction (1 mg scale, 1 mL) using the azide-DBCO conjugation reaction shown in FIG.17A. Results are shown in FIGs.18A to 18E. Additional conjugations were performed using the azide-DBCO conjugation reaction shown in FIGs.17B and 17D. Results are shown in FIGs.20A to 20D. Tz-TCO conjugation An alternative strategy for Tz-TCO conjugation (FIGs.17B and 17C) was used and GPC was performed (FIGs.19A to 19B). Results are shown in FIGs.20A to 20D. FPLC protein separation was performed (FIG.21A to 21C). Dye labeled polymers for conjugation were synthesized (FIGs.22A to 22C). ROMP for drug conjugated MMs FIGs.23A to 23E show ROMP for drug conjugated MMs. FIGs.24A to 24I show block or statistic polymerizations for ROMP of drug conjugated MMs. FIGs.25A to 25B show anti- HER-2 ABCs. (E)-3-(2-(dodecylthio)phenyl)-N-(prop-2-yn-1-yl)prop-2-en-1- amine (3) This compound was prepared according to the method disclosed in J. Am. Chem. Soc. 2018, 140, 38, 12181–12188. (E)-5-((3-(2-(dodecylthio)phenyl)allyl)(prop-2-yn-1-yl)amino )-5-oxopentanoic acid (4) 3 (872 mg, 2.35 mmol, 1 eq.) was dissolved in 3 mL of dichloromethane. A small crystal of 4-(dimethyamino)pyridine was added. Glutaric anhydride (321 mg, 2.82 mmol, 1.2 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford (E)-5- ((3-(2-(dodecylthio)phenyl)allyl)(prop-2-yn-1-yl)amino)-5-ox opentanoic acid (4) (847 mg, 74% yield) as a waxy yellow solid. ¹ H NMR (400 MHz, CDCl3) δ 7.47 – 7.37 (m, 1H), 7.33 (dt, J = 7.9, 2.0 Hz, 1H), 7.27 – 7.12 (m, 3H), 7.04 (dd, J = 15.7, 12.3 Hz, 1H), 6.03 (dt, J = 15.7, 5.7 Hz, 1H), 4.37 – 3.98 (m, 4H), 2.85 (t, J = 7.4 Hz, 2H), 2.61 – 2.44 (m, 4H), 2.33 – 2.20 (m, 1H), 2.03 (h, J = 7.3 Hz, 2H), 1.61 (p, J = 7.5 Hz, 2H), 1.40 (p, J = 7.4 Hz, 2H), 1.25 (s, 16H), 0.88 (t, J = 6.8 Hz, 3H). 2,5-dioxopyrrolidin-1-yl (E)-5-((3-(2-(dodecylthio)phenyl)allyl)(prop-2-yn-1-yl)amino )-5- oxopentanoate (5) 4 (256 mg, 0.53 mmol, 1 eq.), N-hydroxysuccinimide (132 mg, 1.15 mmol, 2.2 eq), and a small crystal of DMAP were dissolved in 2 mL of anhydrous dichloromethane. The flask was then evacuated and back-filled with nitrogen 3x. In a separate vial, 1-(3-dimethylaminopropyl)-3- ethylcarbodiimide hydrochloride (204 mg, 1.06 mmol, 2 eq.) was suspended in 5 mL of anhydrous dichloromethane. The suspension was slowly injected into the reaction flask over 5 minutes with a syringe fitted with a thick needle. The reaction was monitored by thin layer silica gel chromatography (EtOAc/Hexanes). Upon complete consumption of 4, 10 mL of water was added to the reaction and stirred for 10 minutes. The heterogeneous mixture was transferred to a separatory funnel, and the aqueous layer discarded. The organics were washed with 2x10mL water followed by 1x10mL brine. The solution was dried with anhydrous Na2SO4, decanted, and evaporated. The residue was purified by silica gel column chromatography (EtOAc/Hexanes) to afford 2,5-dioxopyrrolidin-1-yl (E)-5-((3-(2-(dodecylthio)phenyl)allyl)(prop-2-yn-1-yl)amino )-5- oxopentanoate (5) (201 mg, 65% yield). ¹ H NMR (500 MHz, CDCl3) δ 7.47 – 7.39 (m, 1H), 7.36 – 7.30 (m, 1H), 7.25 – 7.12 (m, 2H), 7.10 – 6.97 (m, 1H), 6.08 – 5.99 (m, 1H), 4.35 – 4.02 (m, 4H), 2.88 – 2.68 (m, 8H), 2.66 – 2.56 (m, 2H), 2.33 – 2.20 (m, 1H), 2.15 (h, J = 6.9 Hz, 2H), 1.61 (p, J = 7.2 Hz, 2H), 1.40 (p, J = 7.1 Hz, 2H), 1.26 (s, 16H), 0.88 (t, J = 7.2 Hz, 3H). (E)-3-(2-methoxyphenyl)-N-(prop-2-yn-1-yl)prop-2-en-1-amine (7) o-methoxycinnamaldehyde (9.93 g, 61.3 mmol, 1 eq.) was dissolved in 60 mL of methanol. Propargylamine (6.78 g, 123 mmol, 2 eq.) was added to the solution and stirred at 30 °C. Upon complete consumption of o-methoxycinnamaldehyde by crude NMR, the solution was cooled to 0 °C with an ice bath. Then, NaBH ₄ (4.65 g, 123 mmol, 2 eq.) was carefully added to the solution over 5 minutes. The reaction was allowed to come to room temperature and stirred overnight. The methanol was evaporated under reduced pressure, and the residue was dissolved in 50 mL of EtOAc. The solution was then washed with 2x30mL water and 1x30 mL brine. The organic layer was then dried with anhydrous Na ₂ SO ₄ , decanted, and evaporated. The resulting crude product was purified by short-path vacuum distillation to afford (E)-3-(2-methoxyphenyl)- N-(prop-2-yn-1-yl)prop-2-en-1-amine (7) (5.75 g, 47% yield) as a yellow oil. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.43 (dd, J = 7.7, 1.6 Hz, 1H), 7.26 – 7.17 (m, 1H), 6.96 – 6.81 (m, 3H), 6.29 (dt, J = 16.0, 6.4 Hz, 1H), 3.84 (s, 3H), 3.51 (dd, J = 6.5, 1.5 Hz, 2H), 3.47 (d, J = 2.4 Hz, 2H), 2.24 (t, J = 2.4 Hz, 1H), 1.32 (s, 1H). (E)-5-((3-(2-methoxyphenyl)allyl)(prop-2-yn-1-yl)amino)-5-ox opentanoic acid (8) 7 (911 mg, 4.53 mmol, 1 eq.) was dissolved in 9 mL of dichloromethane. A small crystal of 4-(dimethylamino)pyridine was added. Glutaric anhydride (573 mg, 4.98 mmol, 1.1 eq) was added, and the solution was stirred at room temperature. The reaction was monitored by thin layer silica gel chromatography (50% EtOAc/Hexanes). Upon complete consumption of 7, the solution was concentrated under reduced pressure. The residue was purified by silica gel

chromatography (33% - 66% EtOAc/Hexanes) to afford 1.22 g (85% yield) of (E)-5-((3-(2- methoxyphenyl)allyl)(prop-2-yn-1-yl)amino)-5-oxopentanoic acid (8) as a viscous yellow oil. ¹ H NMR (400 MHz, CDCl3) δ 10.54 (s, 1H), 7.45 – 7.35 (m, 1H), 7.28 – 7.19 (m, 1H), 6.97 – 6.77 (m, 3H), 6.20 – 6.06 (m, 1H), 4.32 – 4.00 (m, 4H), 3.85 (s, 3H), 2.60 – 2.43 (m, 4H), 2.31 – 2.20 (m, 1H), 2.10 – 1.96 (m, 2H). (E)-5-((3-(2-methoxyphenyl)allyl)(prop-2-yn-1-yl)amino)-5-ox obutanoic acid (9) 7 (948 mg, 4.72 mmol, 1 eq.) was dissolved in 9 mL of dichloromethane. A small crystal of 4-(dimethylamino)pyridine was added. Succinic anhydride (519 mg, 5.19 mmol, 1.1 eq) was added, and the solution was stirred at room temperature. The reaction was monitored by thin layer silica gel chromatography (4% MeOH/DCM). Upon complete consumption of 7, the reaction was transferred to a separatory funnel and washed with 2x5mL 1M HCl and 1x5mL brine. The organic layer was dried with anhydrous sodium sulfate, evaporated under reduced pressure, and purified by silica gel chromatography (MeOH/DCM) to afford 1.21 g (85% yield) of (E)-5-((3-(2-methoxyphenyl)allyl)(prop-2-yn-1-yl)amino)-5-ox obutanoic acid (9) as a viscous yellow oil. ¹ H NMR (400 MHz, CDCl ₃ ) δ 11.04 (s, 1H), 7.45 – 7.36 (m, 1H), 7.29 – 7.19 (m, 1H), 6.97 – 6.79 (m, 3H), 6.23 – 6.06 (m, 1H), 4.33 – 4.04 (m, 4H), 3.85 (s, 3H), 2.86 – 2.70 (m, 4H), 2.33 – 2.22 (m, 1H). (E)-N-(3-(2-methoxyphenyl)allyl)-N-(prop-2-yn-1-yl)acetamide (10) 7 (559 mg, 2.78 mmol, 1 eq.) and triethylamine (0.47 mL, 3.34 mmol, 1.2 eq) were dissolved in 3 mL of dichloromethane. A small crystal of 4-(dimethylamino)pyridine was added, and the solution was cooled to 0 °C with an ice bath. Acetic anhydride (340 mg, 3.34 mmol, 1.2 eq.) was added to the stirred solution. The ice bath was removed after the addition. After 2 hours, the solution was evaporated under reduced pressure. The residue was purified by silica gel chromatography (50% EtOAc/Hexanes) to afford 587 mg (87% yield) of (E)-N-(3-(2- (butylthio)phenyl)allyl)-N-(prop-2-yn-1-yl)acetamide (10) as a yellow oil. ¹ H NMR (500 MHz,

M1237.70123WO00 125/165 10807651.1 CDCl ₃ ) δ 7.44 – 7.37 (m, 1H), 7.28 – 7.18 (m, 1H), 6.96 – 6.79 (m, 3H), 6.22 – 6.09 (m, 1H), 4.30 – 4.00 (m, 4H), 3.85 (s, 3H), 2.30 – 2.20 (m, 1H), 2.18 (s, 3H). 2-(butylthio)benzaldehyde (11) 1-Butanethiol (20.9g, 232 mmol, 1 eq.) was dissolved in 25 mL of DMSO.39 g (282 mmol, 1.2 eq.) of oven-dried K2CO3 was added to the flask and the resulting heterogeneous mixture was stirred and cooled to 0 °C with an ice bath.43 g (347 mmol, 1.5 eq.) of 2- fluorobenzaldehye was slowly added to the stirred mixture over 2 minutes. The mixture was then heated to 60 °C and stirred overnight. Upon complete consumption of 1-butanethiol as monitored by crude NMR, the flask was fitted with a short-path vacuum distillation apparatus and fractionated under vacuum.29.4g (151 mmol, 65% yield) of 2-(butylthio)benzaldehyde (11) was isolated as a yellow oil. ¹ H NMR (400 MHz, CDCl3) δ 10.39 (s, 1H), 7.83 (dd, J = 7.7, 1.5 Hz, 1H), 7.51 (ddd, J = 8.0, 7.2, 1.6 Hz, 1H), 7.42 (dd, J = 8.0, 1.1 Hz, 1H), 7.29 (td, J = 7.4, 1.1 Hz, 1H), 2.95 (d, J = 7.4 Hz, 2H), 1.68 (p, J = 7.5 Hz, 2H), 1.48 (h, J = 7.7 Hz, 2H), 0.94 (t, J = 7.3 Hz, 3H). (E)-3-(2-(butylthio)phenyl)acrylaldehyde (12) 11 (29.4g, 151 mmol, 1 eq.) was dissolved in 151 mL of absolute ethanol and cooled to 0 °C with an ice bath.8.7 g (198 mmol, 1.3 eq.) of cold acetaldehyde was added to the solution. 68 mL of 1M aqueous NaOH solution (69 mmol, 0.45 eq) was added to the ethanolic solution. Shortly after the addition, the solution turns yellow and cloudy as the product begins to precipitate. The temperature was maintained at 0 °C and the reaction was monitored by crude NMR. Upon complete consumption of acetaldehyde, the precipitated product was allowed to settle to the bottom of the flask, and the supernatant was decanted. The precipitated product was washed by adding 50 mL of cold 1:1 v/v EtOH/H2O to the flask, stirring for five minutes, and decanting off the supernatant. This was repeated once more for a total of two washes. Finally, the crude product was recrystallized from methanol to afford 133g (60 mmol 40% yield) of (E)-3- (2-(butylthio)phenyl)acrylaldehyde (12) as a yellow solid. ¹ H NMR (400 MHz, CDCl ₃ ) δ 9.76 (d, J = 7.8 Hz, 1H), 8.14 (d, J = 15.9 Hz, 1H), 7.61 (dd, J = 7.7, 1.5 Hz, 1H), 7.46 (dd, J = 7.9, 1.3 Hz, 1H), 7.37 (td, J = 7.6, 1.5 Hz, 1H), 7.32 – 7.20 (m, 1H), 6.67 (dd, J = 15.9, 7.8 Hz, 1H), 2.91 (t, J = 7.3 Hz, 2H), 1.63 (p, J = 7.6 Hz, 2H), 1.46 (h, J = 7.6 Hz, 2H), 0.92 (t, J = 7.3 Hz, 3H). (E)-3-(2-(butylthio)phenyl)-N-(prop-2-yn-1-yl)prop-2-en-1-am ine (13) 12 (2.81g, 12.8 mmol, 1 eq.) was dissolved in 26 mL of methanol. Propargylamine (1.06g, 19.2 mmol, 1.5 eq.) was added to the solution and stirred at room temperature. Upon complete consumption of 12 by crude NMR, the solution was cooled to 0 °C with an ice bath. Then, NaBH ₄ (0.97 g, 25.6 mmol, 2 eq.) was added to the solution and the reaction was stirred overnight. The solution was concentrated under reduced pressure, and the residue was dissolved in 30 mL of EtOAc. The solution was then washed with 2x30mL water and 1x30 mL brine. The organic layer was dried with anhydrous Na2SO4, decanted, and evaporated. This crude product (13) was used without further purification for subsequent synthetic steps. Alternatively, the crude product can be purified by silica gel column chromatography (EtOAc/Hexanes) to afford an analytical sample of 13. ¹ H NMR (400 MHz, CDCl3) δ 7.48 – 7.44 (m, 1H), 7.39 – 7.29 (m, 1H), 7.22 – 7.13 (m, 2H), 7.08 (dt, J = 15.8, 1.6 Hz, 1H), 6.18 (dt, J = 15.7, 6.4 Hz, 1H), 3.54 (dd, J = 6.4, 1.5 Hz, 2H), 3.49 (d, J = 2.4 Hz, 2H), 2.86 (t, J = 7.3 Hz, 2H), 2.25 (t, J = 2.4 Hz, 1H), 1.61 (p, J = 7.5 Hz, 2H), 1.56 (s, 1H), 1.45 (h, J = 7.7 Hz, 2H), 0.91 (t, J = 7.3 Hz, 3H). (E)-5-((3-(2-(butylthio)phenyl)allyl)(prop-2-yn-1-yl)amino)- 5-oxopentanoic acid (14) Crude 13 (1.78 g, 6.9 mmol, 1 eq.) was dissolved in 10 mL of dichloromethane. A small crystal of 4-(dimethylamino)pyridine was added, and the solution was cooled to 0 °C with an ice bath. Glutaric anhydride (0.91 g, 8.0 mmol, 1.2 eq.) was added, and the reaction was heated to 35 °C for 3 hours. The solution was allowed to cool to room temperature before diluting with 40 mL of diethyl ether. The organic layer was washed with 3x20 mL water, 1x20 mL brine, dried with anhydrous Na ₂ SO ₄ , decanted, and evaporated. Finally, the residue was purified by silica gel chromatography (40% EtOAc/Hexanes + 1% AcOH) to afford 1.14 g (44% yield) of (E)-5-((3- (2-(butylthio)phenyl)allyl)(prop-2-yn-1-yl)amino)-5-oxopenta noic acid (14), a viscous yellow oil. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.47 – 7.37 (m, 1H), 7.37 – 7.30 (m, 1H), 7.27 – 7.12 (m, 2H), 7.10 – 6.98 (m, 1H), 6.03 (dt, J = 15.7, 6.0 Hz, 1H), 4.43 – 4.02 (m, 4H), 2.86 (t, J = 7.1 Hz, 2H), 2.61 – 2.42 (m, 4H), 2.33 – 2.21 (m, 1H), 2.09 – 1.96 (m, 2H), 1.61 (p, J = 7.4 Hz, 2H), 1.44 (h, J = 7.5 Hz, 2H), 0.92 (t, J = 7.3 Hz, 3H). (E)-N-(3-(2-(butylthio)phenyl)allyl)-N-(prop-2-yn-1-yl)aceta mide (15) 1.20g (4.62 mmol, 1 eq.) of crude 13 was dissolved in 10 mL of dichloromethane. A small crystal of 4-(dimethylamino)pyridine was added, and the solution was cooled to 0 °C with an ice bath. Acetic anhydride (0.94 g, 9.24 mmol, 2 eq.) was added, and the solution was stirred and allowed to come to room temperature. After 2 hours, the solution was evaporated under reduced pressure. The residue was purified by silica gel chromatography (40% EtOAc/Hexanes) to afford 329 mg (24% yield) of (E)-N-(3-(2-(butylthio)phenyl)allyl)-N-(prop-2-yn-1- yl)acetamide (15) as a yellow oil. ¹ H NMR (400 MHz, CDCl3) δ 7.47 – 7.38 (m, 1H), 7.35 (dd, J = 7.6, 1.5 Hz, 1H), 7.27 – 7.12 (m, 2H), 7.10 – 7.01 (m, 1H), 6.10 – 5.98 (m, 1H), 4.35 – 4.00 (m, 4H), 2.86 (t, J = 7.4 Hz, 2H), 2.32 – 2.21 (m, 1H), 2.25 – 2.17 (m, 3H), 1.60 (p, J = 7.4 Hz, 2H), 1.44 (h, J = 7.3 Hz, 2H), 0.91 (t, J = 7.3 Hz, 3H). 5 (53 mg, 0.092 mmol, 1.5 eq.) and diisopropylethylamine (32 µL, 0.184 mmol, 3 eq.) were dissolved in 1 mL of dichloromethane at room temperature. H ₂ N-PEG15-NHBoc (50 mg, 0.061 mmol, 1 eq.) was dissolved in a minimal amount of dichloromethane and was added to the stirred solution of 5 and diisopropylethylamine. The reaction was allowed to stir overnight at room temperature. The solution was then evaporated under reduced pressure, and the residue was purified by silica gel chromatography (MeOH/DCM) to afford 16 (57 mg, 72% yield) as a slightly yellow gummy solid. 5 (43 mg, 0.074 mmol, 1.5 eq.) and diisopropylethylamine (26 µL, 0.148 mmol, 3 eq.) were dissolved in 1 mL of dichloromethane at room temperature. H2N-PEG23-NHBoc (58 mg, 0.049 mmol, 1 eq.) was dissolved in a minimal amount of dichloromethane and was added to the stirred solution of 5 and diisopropylethylamine. The reaction was allowed to stir overnight at room temperature. The solution was then evaporated under reduced pressure, and the residue was purified by silica gel chromatography (MeOH/DCM) to afford 17 (51 mg, 64% yield) as a slightly yellow gummy solid. 3 (100 mg, 0.27 mmol, 1 eq.) and Tos-PEG5-CH2COOH (120 mg, 0.297 mmol, 1.1 eq.) were dissolved in 2 mL of dichloromethane.6.6 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (62 mg, 1.2eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 18 (160 mg, 78% yield).

3 (166.2 mg, 0.448 mmol, 1 eq.) and Amino-PEG ₅ -acid (150 mg, 0.448 mmol, 1 eq.) were dissolved in 2 mL of dichloromethane.11 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (103 mg, 1.2eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 19 (277.6 mg, 90% yield). 3 (33 mg, 0.087 mmol, 1.3 eq.) and TCO-PEG3-acid (25 mg, 0.067 mmol, 1 eq.) were dissolved in 1 mL of dichloromethane.1.64 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (21 mg, 1.6 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 20 (48 mg, 99% yield). 3 (43.4 mg, 0.087 mmol, 1.3 eq.) and Methyltetrazine-PEG4-acid (50 mg, 0.115 mmol, 1 eq.) were dissolved in 1 mL of dichloromethane.2.16 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (27.6 mg, 1.6 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 21 (86.9 mg, 96% yield). 3 (39.4 mg, 0.106 mmol, 1.3 eq.) and Methyltetrazine-PEG8-acid (50 mg, 0.0816 mmol, 1 eq.) were dissolved in 1 mL of dichloromethane.2.02 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (23.5 mg, 1.5 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 22 (79 mg, Quantitative yield). 3 (15.5 mg, 0.0416 mmol, 1.3 eq.) and Methyltetrazine-PEG ₁₂ -acid (25 mg, 0.032 mmol, 1 eq.) were dissolved in 1 mL of dichloromethane.0.8 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (9.24 mg, 1.5 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 23 (34.9 mg, 96% yield). 3 (45.3 mg, 0.12 mmol, 1.3 eq.) and t-Boc-N-amido-PEG ₂₀ -acid (100 mg, 0.093 mmol, 1 eq.) were dissolved in 1 mL of dichloromethane.2.29 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (26.6 mg, 1.5 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 24 (122.4 mg, 92% yield). 3 (150 mg, 0.404 mmol, 1 eq.) and BOC-11-AUN-OH (128 mg, 0.424 mmol, 1.05 eq.) were dissolved in 3 mL of dichloromethane.9.9 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (100.6 mg, 1.3 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 25 (264 mg, Quantitative yield). 3 (150 mg, 0.404 mmol, 1 eq.) and BOC-6-AHX-OH (98.2 mg, 0.093 mmol, 1.05 eq.) were dissolved in 1 mL of dichloromethane.9.9 mg of 4-(dimethyamino)pyridine (0.2 eq.) was added. Then, EDC (100.6 mg, 1.3 eq.) was added, and the solution was stirred at room temperature. The reaction was monitored by TLC (5% MeOH/DCM). Upon complete consumption of 3, the solution was evaporated under reduced pressured. The residue was purified by silica gel chromatography (MeOH/DCM) to afford 26 (236 mg, Quantitative yield). Synthesis of exemplary brush polymers In a nitrogen filled glovebox, to a 4-mL scintillation vial charged with a stir bar and containing PEG based MM, dye labelled or drug conjugated MM (100 mg) was added anhydrous THF (400 μL). To this solution then was added Grubbs III catalyst solution in THF, all at once (0.376 mg) to give MM: Grubbs III ratio of 60 : 1. The polymerization reaction was stirred at room temperature for 60 min. Then, different enyne compounds were added for additional 1.5 h reaction to obtain different terminal functional groups. A 10-μL aliquot was taken out for size exclusion chromatography analysis of polymerization product. The remaining brush solution was precipitated in cold ethyl ether and washed with the cold ether for several times. Antibody brush polymer conjugation for ABCs Antibody surface modification with TCO functionality 1 mg of antibody was dissolved in 0.6 mL PBS. Then, 60 μL of 0.5 M NaHCO ₃ buffer solution was added under stirring. To the above solution was added 60 μg of TCO-PEG ₁₂ -NHS The reaction mixture was then stirred at room temperature for an additional 4 h, followed by filtration with a 220 μm filter and an ultrafiltration purification using Amicon Ultra Centrifugal Filters (MWCO = 10,000). The final protein was dissolved in 200 μL of DI water (5 mg/mL) and stored at 4 °C. The modification of the boronic acid linker was quantified by MADLI-MS. In some experiments, TCO-PEGn4-NHS was used, wherein n4 is an integer from 1 to 20, inclusive. In some experiments, TCO-PEG8-NHS was used, Antibody-brush polymer conjugation 30 μL of above TCO functionalized antibody was mixed with 60 μL tetrazine functionalized brush polymer (e.g., (which does not contain a pharmaceutical agent) or a derivative that contains a pharmaceutical agent, 10 mg/mL). The reaction solution was stirred at room temperature for 24 h. Example 2. Anti-HER2 Targeted ABCs Anti-HER2 brush polymers conjugation Mass spectrometry was performed (FIG.5A). SDS-PAGE gels showed successful conjugation due to the smear band in the higher molecular weight and disappearance of the free antibody band (FIG.5B). Anti-HER2 ABCs for cell targeting ABCs were tested in cell lines with high (SKBR-3), medium (SKOV-3), and no (MCF- 10A) HER2 expression. Results showed that ABCs can significantly enhance cell uptake toward HER2 in high (FIGs.6A to 6B) and medium (FIGs.7A to 7B) expression cell lines. ABC could not enhance the cell uptake toward HER2 in the control (FIGs.8A to 8B), demonstrating specificity. ABCs were also shown to significantly enhance cell uptake toward HCC-1954 (HER2 medium expression, FIG.9A) and BT-474 cell lines (HER2 high expression, FIG.9B). Cell toxicity studies ABCs induced significantly higher toxicity compared to brush polymers in HER2 expression cell lines (SKBR-3, SKOV-3), but exhibited similar toxicity toward the control cell line (MCF-10A) (FIGs.10A to 10B). Cell toxicity was evaluated using different conditions in the SKBR-3 (high HER2 expression) cell line. Results show that ABCs can induce significantly higher toxicity compared to brush polymers and free drugs in HER2 expression cell lines. (FIGs.11A to 11D) Cell toxicity was also evaluated in the HCC-1954 and SKOV-3 cell line. Results show that ABCs can induce significantly higher toxicity compared to brush polymers in low and medium HER2 expression cell lines (FIGs.12A to 12B. FIG.13). ABCs exhibited similar toxicity to brush polymers in the control cell line (MCF-10A) without HER2 expression (FIG 14). Cell toxicity studies were performed in SKBR-3 (FIG.15A), HCC-1954 (FIG.15B) and BT-474 (FIG.15C) cell lines with the free antibody as a control. Results show that the antibody itself has no toxicity toward these cell lines. The brush polymer or physical mixture of antibody and brush polymer have similar toxicity, significantly lower than ABCs. Further, we used Anti-BCMA based ABCs for targeted delivery by flow cytometry. Exemplary results are shown in FIGs.16B to 16D. The ABCs show much higher cell uptake than BPD in two different cell lines (MM.1S and KMS-11). Example 3. Cell experiments Cell Culture Different cell lines (including SKBR-3, SKOV-3, MCF-10A, HCC-1954, BT-474) were cultured in T75 cell culture flask containing RMPI or Dulbecco’s Modified Eagle Medium/Nutrient Mixture F-12 (DMEM/F12) in a humidified S26 incubator with 5% CO2 at 37 °C. Culture media was supplemented with 10% fetal bovine serum (FBS), 1% l-glutamine, and 1% antibiotic-antimycotic (100 units/mL of penicillin, 100 μg/mL of streptomycin, and 0.25 μg/mL of amphotericin B). Cellular Uptake Studies based on flow cytometry Cell uptake studies were performed with different cell lines, seeded at 150^000 cells/mL 24 well plate and cultured for 24 h at 37 °C in a 5% CO2 incubator. The medium was discarded and cells were then incubated with 0.5 mL of medium containing different materials (including ABCs, brush polymers or control ABCs) for different times. After washing the cells with cold PBS, the mean fluorescence intensity within the cells was quantified using flow cytometry. Cell Viability by MTT Assay Different cells (including SKBR-3, SKOV-3, MCF-10A, HCC-1954, BT-474) were seeded into 96-well tissue culture plates at a density of 10^000 cells/well/100 μL sample and incubated at 37 °C. After 24 h, culture media was replaced and cells were treated with different concentrations of brush polymers in 100 μL media (10 μL protein containing solution with different concentrations + 90 μL medium). At the desired time interval, the medium was removed and the cells were cultured by 100 μL 10% MTT (5 mg/mL) in medium solution for another 4 h. Then the solution was discarded and the remaining crystal was dissolved by 100 μL DMSO The solution was subjected to absorbance measurement with SpectraMax M5 at 590 nm. Cell death was measured by the MTT assay in triplicate. EQUIVALENTS AND SCOPE In the claims articles such as “a,” “an,” and “the” may mean one or more than one unless indicated to the contrary or otherwise evident from the context. Claims or descriptions that include “or” between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context. The invention includes embodiments in which exactly one member of the group is present in, employed in, or otherwise relevant to a given product or process. The invention includes embodiments in which more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process. Furthermore, the invention encompasses all variations, combinations, and permutations in which one or more limitations, elements, clauses, and descriptive terms from one or more of the listed claims is introduced into another claim. For example, any claim that is dependent on another claim can be modified to include one or more limitations found in any other claim that is dependent on the same base claim. Where elements are presented as lists, e.g., in Markush group format, each subgroup of the elements is also disclosed, and any element(s) can be removed from the group. It should it be understood that, in general, where the invention, or aspects of the invention, is/are referred to as comprising particular elements and/or features, certain embodiments of the invention or aspects of the invention consist, or consist essentially of, such elements and/or features. For purposes of simplicity, those embodiments have not been specifically set forth in haec verba herein. It is also noted that the terms “comprising” and “containing” are intended to be open and permits the inclusion of additional elements or steps. Where ranges are given, endpoints are included. Furthermore, unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value or sub-range within the stated ranges in different embodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise. This application refers to various issued patents, published patent applications, journal articles, and other publications, all of which are incorporated herein by reference. If there is a conflict between any of the incorporated references and the instant specification, the specification shall control. In addition, any particular embodiment of the present invention that falls within the prior art may be explicitly excluded from any one or more of the claims Because such embodiments are deemed to be known to one of ordinary skill in the art, they may be excluded even if the exclusion is not set forth explicitly herein. Any particular embodiment of the invention can be excluded from any claim, for any reason, whether or not related to the existence of prior art. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments described herein. The scope of the present embodiments described herein is not intended to be limited to the above Description, but rather is as set forth in the appended claims. Those of ordinary skill in the art will appreciate that various changes and modifications to this description may be made without departing from the spirit or scope of the present invention, as defined in the following claims.