CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to and the benefit of United States patent application no. 63/196,312, “Thermally Activated Reversible Adhesive Films With Fast Hardening” (filed June 3, 2021), the entirety of which application is incorporated herein by reference for any and all purposes.

TECHNICAL FIELD

[0002] The present disclosure relates to the field of thermally-activated adhesive films.

BACKGROUND

[0003] Adhesives are ubiquitous in daily life, in construction, automobile manufacture, wound dressing/healing, of medical devices, cosmetics, and in microchip assemblies. Adhesives can generally be divided into two classes: (1) strong but irreversible super glues, such as cyanoacrylate-based adhesives; and (2) weak but reversible adhesives, such as various pressure sensitive adhesives. Both have advantages and disadvantages; strong but irreversible adhesives are often responsible for destructive delamination and thus accumulated waste, while reversible adhesives fail to provide strong enough load transmission for various applications.

[0004] Two examples include construction and wound adhesives. Using roof top adhesives as an example, commercial adhesives for roof-top membranes are strong but irreversible. Consequently, in case of any rework or replacement, a complete set of new membranes are required as the peeling process between membranes are destructive. In the case of wound adhesives, pressure sensitive adhesive (PSA) represents a facile treatment for epidermic cuts. However, PSA normally lasts only for days, and even less if it encounters water, which is inevitable in daily life. In both cases, strong and reversible adhesives depict an obvious solution, which is plagued by the inverse relationship between adhesion strength and reversibility. [0005] Previous attempts to address strong and reversible adhesion resulted in either compromised adhesion performance or complicated engineering and specific application conditions. Adhesives using finely constructed surface topology to accumulate van der Waals forces demonstrated, at best, adhesion one-order-of magnitude lower than super glue (120 N/cm ² versus 1000 N/cm ² for super glue). Double interpenetrating networks (IPNs) provide strong adhesion, but only in wet environments and revolve around complicated composition and layered fabrication. Accordingly, there is a long-felt need for eversible adhesive compositions and also for related methods.

SUMMARY

[0006] In meeting the described long-felt needs, the present disclosure provides polymer compositions, comprising: a polymeric hydrogel; and a thermoresponsive polymer, the polymeric hydrogel and the thermoresponsive polymer being arranged as an interpenetrating network, the thermoresponsive polymer being soluble in water, the thermoresponsive polymer having a lower critical solution temperature (LCST), and the thermoresponsive polymer chains being dispersed within the polymeric hydrogel such that when the thermoresponsive polymer attains a temperature above the LCST, the thermoresponsive polymer becomes insoluble and forms physical crosslinks between chains of the polymeric hydrogel.

[0007] Also provided are articles, comprising a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20) disposed on a substrate.

[0008] Further provided are articles, the articles comprising a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20) disposed so as to bond two portions of a substrate to one another.

[0009] Also disclosed are articles, the articles comprising a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20) disposed so as to bond two substrates to one another.

[0010] Further provided are kits, comprising an applicator and an amount of a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20), the applicator configured to controllably dispense the polymer composition.

[0011] Also provided are methods, comprising: effecting heating of a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20) such that the thermoresponsive polymer attains a temperature above the LCST of the thermoresponsive polymer, or effecting cooling of a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20) such that the thermoresponsive polymer attains a temperature below the LCST of the thermoresponsive polymer.

[0012] Further provided are methods, comprising using a polymer composition according to the present disclosure (e.g., any one of Aspects 1-20) to bond a first substrate to a second substrate; the methods can also be performed to bond two portions of a substrate to one another.

[0013] Also disclosed are methods, comprising: dispersing a thermoresponsive polymer into a hydrogel precursor, the thermoresponsive polymer being soluble in water, the thermoresponsive polymer having a lower critical solution temperature (LCST), and the thermoresponsive polymer chains being dispersed within the polymeric hydrogel such that when the thermoresponsive polymer attains a temperature above the LCST, the thermoresponsive polymer becomes insoluble and forms physical crosslinks between chains of the polymeric hydrogel.

[0014] The disclosed technology is illustrated by the strong and reversible adhesion of poly (2 -hydroxy ethyl methacrylate) (PHEMA) hydrogels that include an additional poly(N-isopropylacrylamide) (PNIPAm) segment, which additional segment introduces thermal response through lower critical solution temperature (LCST) and significantly reduces the adhesion evolution time (from 60 - 90 minutes to 2 minutes) at T > LCST. It should be understood, however, that the PHEMA-PNIPAm materials used to illustrate certain aspects of the disclosed technology are illustrative only and that the example PHEMA-PNIPAm materials do not limit the scope of the present disclosure or the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various aspects discussed in the present document. In the drawings: [0015] FIG. 1 provides an exemplary composition according to the present disclosure;

[0016] FIG. 2 provides exemplary results from an illustrative composition according to the present disclosure; and

[0017] FIGs. 3 A-3B illustrate lap shear adhesion of a partially hydrated PHEMA film, showing the influence of (FIG. 3A) film thickness (hydration time = 30 min) and (FIG. 3B) hydration time (film thickness = 210 pm).

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0018] The present disclosure may be understood more readily by reference to the following detailed description of desired embodiments and the examples included therein.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0020] The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0021] As used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of' and "consisting essentially of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps. However, such description should be construed as also describing compositions or processes as "consisting of and "consisting essentially of' the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps. [0022] As used herein, the terms “about” and “at or about” mean that the amount or value in question can be the value designated some other value approximately or about the same. It is generally understood, as used herein, that it is the nominal value indicated ±10% variation unless otherwise indicated or inferred. The term is intended to convey that similar values promote equivalent results or effects recited in the claims. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about” or “approximate” whether or not expressly stated to be such. It is understood that where “about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0023] Unless indicated to the contrary, the numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0024] All ranges disclosed herein are inclusive of the recited endpoint and independently of the endpoints (e.g., "between 2 grams and 10 grams, and all the intermediate values includes 2 grams, 10 grams, and all intermediate values"). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and/or values. All ranges are combinable.

[0025] As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially,” may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints.

For example, the expression “from about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” may refer to plus or minus 10% of the indicated number. For example, “about 10%” may indicate a range of 9% to 11%, and “about 1” may mean from 0.9-1.1. Other meanings of “about” may be apparent from the context, such as rounding off, so, for example “about 1” may also mean from 0.5 to 1.4. Further, the term “comprising” should be understood as having its open-ended meaning of “including,” but the term also includes the closed meaning of the term “consisting.” For example, a composition that comprises components A and B may be a composition that includes A,

B, and other components, but may also be a composition made of A and B only. Any documents cited herein are incorporated by reference in their entireties for any and all purposes.

[0026] The present disclosure relates to hydrogels providing strong and reversible adhesion with a temperature-controlled fast hardening trigger. An example of such a composition is an interpenetrating polymeric precursor based on 2-hydroxy ethyl methacrylate (HEMA) and N-isopropylacrylamide (NIP Am), which composition can optionally include a miscible crosslinker and radical initiator.

[0027] The present disclosure alleviates the problematic trade-off between adhesion strength and adhesion reversibility. As an example, a PHEMA hydrogel with relatively low modulus (200 kPa) adapts to rough surfaces and guarantees good contact between hydrogel and substrates. Upon dehydration, the modulus of PHEMA gel increases significantly to 2.3 GPa, which increase locks the shape adaption in hydrogel and provides a strong load transition (strong adhesion). After rehydration, the modulus decreases back to 200 kPa, affording easy recycling as an intact adhesive film. Hence, PHEMA adhesive without PNIPAm segment can serve as a strong and reversible adhesive, albeit with a relatively slowly evolving adhesion force (60 to 90 minutes to achieve high adhesion).

[0028] As shown herein, PHEMA/PNIPAm can adhere to substrates within minutes (< 2 min) when T > LCST. At T > LCST, PNIPAm becomes insoluble aggregates in the hydrogel which physically crosslinks the hydrogel (FIG. 1). The additional physical crosslink provides fast hardening to accelerate the soft-hard transition in PHEMA hydrogel. The LCST of PNIPAm is tunable through the molecular weight of NIP Am to meet various working temperatures.

[0029] One object of this disclosure is providing a new adhesive formula with strong and reversible adhesion, and the time of adhesion can be further decreased to under 2 minutes. Although PHEMA is used as an illustrative hydrogel polymer, other polymers can be used, e.g., other hydroxyl group-rich polymers instead of PHEMA, such as polysaccharides and alginates. Likewise, PNIPAm is merely an example model thermal responsive polymer with LCST behavior. Other thermally-responsive polymers with LOST behavior can provide similar fast adhesion. Additives can optionally be used to modulate the properties of the disclosed compositions; example additives include (but are not limited to) cellulose nanocrystals (CNCs), salts, cellulose ether, and ionic liquids.

[0030] As an example, the forgoing and other objectives can be achieved by adhesive compositions that comprise an interpenetrating polymeric precursor based on 2- hydroxyethyl methacrylate (HEMA) and N-isopropylacrylamide (NIP Am, optional). The compositions can also include a miscible crosslinker and a radical initiator.

[0031] HEMA and NIP Am monomer are both commercially available and can be used without any pre-treatment. PNIPAm with a particular molecular weight can be synthesized through radical polymerization and dissolved in HEMA monomer. The mixture can be further oligomerized with the addition of radical polymerization. Finally, crosslinker and more radical initiator are introduced to the mixture. A cured gel is then submerged in water to form soft hydrogel. The formed hydrogel undergoes shape adaption to targeted surfaces and formed strong adhesion upon dehydration. The adhesion emerges significantly faster when T > LCST of PNIPAm.

[0032] The choice of the molecular weight of PNIPAm can depend on the selected application. For wound adhesives, the molecular weight of PNIPAm is chosen so that the LSCT is close to body temperature (37 °C). For applications that require lower working temperature, a longer PNIPAm is preferred as LCST decreases with increasing PNIPAm molecular weight; however, increasing molecular weight of PNIPAm leads to higher viscosity for the hydrogel precursor. The PNIPAm (or other therm oresponsive polymer) can have a molecular weight (and LCST) that is based on the application of interest.

[0033] Without being bound to any particular theory, the ratio of HEMA/NIPAm can dictate adhesion strength. As the modulus of PNIPAm is significantly lower than PHEMA (both wet and dry modulus), the final adhesion can benefit from a high HEMA/NIPAm ratio. But at T > LCST, PNIPAm, as physical crosslinker, enhanced the gel modulus through increased crosslinking density. As a result, a fast adhesion favors low HEMA/NIPAm ratio. Thus, an intermediate HEMA/NIPAm ratio can provide the optimized fast and strong adhesion. The intermediate HEMA/NIPAm ratio also varies with the molecular weight of PNIPAm.

[0034] A crosslinker can be selected on the basis of good miscibility with the polymer mixture. The crosslinker concentration can vary form 2 vol% to 8 vol% without significant influence on the adhesion performance. An initiator can also be selected on the basis of good miscibility with the polymer mixture. The initiator concentration can vary form 2 v% to 8 v% without significant influence on the adhesion performance.

[0035] As shown here, example adhesion tests consisted of crosslinking a square PHEMA/PNIPAm film under UV (with photo-induced radical initiator). The cured film is submerged in water overnight to reach full hydration (hydrogel). (It should be understood, however, that the disclosed compositions need not be fully hydrated to operate, but full hydration can be useful in some embodiments.) The hydrogel was directly sandwiched between two glass slides with two clippers to ensure good contact. After a certain amount of time at a specific temperature, the clippers were removed, and the glass slides were tested in a lap shear set-up: one glass slide was fixed on a clamp while various weights were attached to the other glass slide.

[0036] The following examples illustrate the disclosed technology and should not be considered as limiting.

[0037] Example 1 - Control

[0038] This example illustrates the slow adhesion evolution from a PHEMA hydrogel without a NIP Am segment.

[0039] HEMA monomers with 1.5 v% Darocure 1173 (photo-initiator) were exposed to 3000 J/cm ² UV (365 nm) with 30 S vortex after every 1000 J/cm ² . The mixture was settled for 1 h in dark before the addition of 2 v% ethylene glycol dimethacrylate (EGDMA, crosslinker) and 1 v% of Darocure 1173. The mixture was homogenized using ultrasoni cation for 20 min. The resulting precursor was directly poured into square mold with PDMS lid on top to ensure flat top surface before exposure to 365 nm UV for 20000 J/cm ² dose. The cured film was soaked in deionized (DI) water overnight for complete hydration, although complete hydration is not a requirement.

[0040] The hydrogel (0.9 ^c 0.9 inch) was sandwiched between two glass slides and dried at 40 °C for 2 minutes and demonstrates essentially no adhesion; however, the completely dried hydrogel between glass slides shows strong adhesion comparable to super glue. Rehydration of the poly(HEMA) gel leads to the detachment of the adhesive as an intact film.

[0041] Example 2

[0042] This example demonstrates the influence of PNIPAm molecular weight on fast adhesion.

[0043] PNIPAm was synthesized through photo-induced radical polymerization in water: 1.5 g of NIP Am monomer was dissolved in 6 mL DI water before addition of 0.75/1.5/3.0 v% Daracure 1173 (corresponding to 5000/2500/1250 g/mol theoretical molecular weight). PNIPAm precipitated out from water through the emulsion polymerization after a 2000 J/cm ² UV dose. DI water was decanted, and PNIPAm was dried in an oven (65 °C) for 2 h. The dried PNIPAm was cut into minute pieces and dissolved in HEMA monomer (molar ratio HEMA/NiPAM = 96/4). The HEMA monomers with dissolved PNIPAm underwent the same procedure in Example 1 to produce hydrogels.

[0044] The hydrogel (0.9 ^c 0.9 inch) was sandwiched between two glass slides and dried at 40 °C for 2 minutes and demonstrates different adhesion strengths (FIG. 2). A PHEMA/PNIPAm hydrogel with 5000 g/mol and 1250 g/mol PNIPAm exhibits weak adhesion (> 5 g) after 2 minutes heating at 40 °C, while a 2500 g/mol PNIPAm provides strong adhesion (> 300 g). In all three cases, the adhesion continued to increase until the hydrogel is fully dehydrated. If the drying temperature is raised to 65 °C for 5 minutes, the above three composition all showed strong adhesion (> 300 g).

[0045] Example 3

[0046] This example illustrates the influence of HEMA/NIPAm ratio on fast adhesion.

[0047] PNIPAm with number average molecular weight (M _n ) of 2500 g/mol was synthesized following the procedures in Example 2. When dissolving poly(NIPAm) in HEMA monomers, different HEMA/NIPAm molar ratios were targeted: 96/4, 92/8, and 87.5/12.5. The hydrogel films fabricated through the procedures in Example 2 demonstrated different adhesive properties (FIG. 2). After drying at 40 °C for 2 minutes, low HEMA/NIPAm ratios showed limited adhesion ( > 5 g) while high HEMA/NIPAm ratio (96/4) adhered strongly to the glass surfaces (> 300 g).

[0048] Example 4 [0049] This example illustrates water resistance of the PHEMA/PNIPAm adhesive after the fully development of the adhesion force. A hydrogel composed of 12.5 mol% 2500 g/mol PNIPAm was fabricated through the procedures in Example 2. The hydrogel was sandwiched between two glass slides and allowed to be fully developed for 2 h. The resulting adhesive was exposed to DI water, and its adhesion was tested every 15 minutes. After 120 minutes, the adhesive fails, thus showing significant water resistance.

[0050] Additional Disclosure

[0051] It was observed that a partially hydrated PHEMA film (crosslinked with EGDMA) exhibited a comparatively rapid and strong adhesion, e.g., within about 2 minutes, illustrating that an amount of PHEMA can be hydrated for a relatively short time (e.g., 30-60 minutes) and then achieve comparatively strong adhesion.

[0052] As an example, PHEMA hydrated for 30 minutes can be applied as an adhesive film directly; increasing the film thickness from 45 pm to 210 pm improved the adhesion from 12.7 N/cm ² to 17.9 N/cm ² after 2 min of adhering (FIG. 3 A). Extending the hydration time from 30 min to 45 and 60 min (for a 210 pm thick film), the lap shear adhesion firstly increased to 27.0 N/cm ² and then declined to 10.4 N/cm ² , demonstrating an optimized hydration time for fast adhesion (e.g., 2 min) of 45 min (FIG. 3B). Without being bound to any particular theory or embodiment, adhesion in a partial hydrated films relies on the balance between surface softening (to conform easily to the surface of the adherend) and fast water evaporation (to more quickly complete the adhesion process).

[0053] PNIPAm (or other thermoresponsive polymers) can also be added into a PHEMA system to further enhance adhesion speed, e.g., with temperature response (37 °C). Such a system need not be fully hydrated and can instead be partially hydrated.

[0054] Aspects

[0055] The following Aspects are illustrative only and do not limit the scope of the present disclosure or the appended claims.

[0056] Aspect 1. A polymer composition, comprising: a polymeric hydrogel; and a thermoresponsive polymer, the polymeric hydrogel and the thermoresponsive polymer being arranged as an interpenetrating network, the thermoresponsive polymer being soluble in water, the thermoresponsive polymer having a lower critical solution temperature (LCST), and the thermoresponsive polymer chains being dispersed within the polymeric hydrogel such that when the thermoresponsive polymer attains a temperature above the LCST, the thermoresponsive polymer becomes insoluble and forms physical crosslinks between chains of the polymeric hydrogel.

[0057] The composition can be present as, e.g., a film. Such a film can have a thickness of, e.g., from about 10 to about 1000 pm, or from about 20 to about 500 pm, or from about 50 to about 300 pm, or even from about 100 to about 200 pm. The composition can be incorporated into a bandage (e.g., a bandage with a removable/peelable backing), as one example use.

[0058] Aspect 2. The polymer composition of Aspect 1, wherein the hydrogel matrix comprises a polymer having one or more of -ML, -COOH, -OH, -CONH ₂ , - CONH -, and -SO ₃ H as a side group and/or end group.

[0059] Aspect 3. The polymer composition of Aspect 2, wherein the polymeric hydrogel comprises a polymer having -OH as a side group in repeat units of the polymer, having -OH at terminations of the polymer (e.g., as an end group), or both.

[0060] Aspect 4. The polymer composition of Aspect 2, wherein the polymeric hydrogel comprises a polysaccharide or an alginate. A polysaccharide can be, e.g., a starch, a cellulose, or chitin. An alginate can include various cations, e.g., sodium and/or calcium.

[0061] Aspect 5. The polymer composition of Aspect 1, wherein the polymeric hydrogel comprises poly(2-hydroxyethyl methacrylate) (PHEMA).

[0062] Aspect 6. The polymer composition of any one of Aspects 1-5, wherein the LCST of the thermoresponsive polymer is about 37 °C.

[0063] Aspect 6. The polymer composition of any one of Aspects 1-5, wherein the LCST of the thermoresponsive polymer is below 37 °C.

[0064] Aspect 8. The polymer composition of any one of Aspects 1-7, wherein the thermoresponsive polymer comprises poly(N-isopropylacrylamide) (PNIiPAmM), polyvinyl methyl ether, poly(vinylcaprolactam), a poloxamer, or any combination thereof.

[0065] Aspect 9. The polymer composition of any one of Aspects 1-8, further comprising a crosslinker that chemically crosslinks chains of the polymeric hydrogel.

[0066] Aspect 10. The polymer composition of Aspect 9, wherein the crosslinker comprises ethylene glycol dimethacrylate (EGDMA).

[0067] Aspect 11. The polymer composition of any one of Aspects 1-10, further comprising cellulose nanocrystals, salt, cellulose ether, an ionic liquid, anisotropic bodies, or any combination thereof. [0068] Aspect 12. The polymer composition of Aspect 11, wherein an anisotropic body comprises cellulose nanocrystals, cellulose nanofibers, cellulose microfibers, hydrogels, or any combination thereof.

[0069] A cellulose nanocrystal can have a diameter in the range of tens of nanometers and a length in the range of from about 1 to about 100 microns, e.g., from about 1 to about 100 microns, from about 5 to about 90 microns, from about 10 to about 80 microns, from about 20 to about 70 microns, from about 30 to about 60 microns, or even from about 40 to about 50 microns. A cellulose nanofiber can have a diameter in the range of tens of nanometers, and a length in the range of from about 1 to about 10 microns. A cellulose microfiber can have a diameter in the range of from about 1 to about 10 microns and a length of from about 10 to about 1000 microns. A hydrogel can include one or more anisotropic nanofillers such as cellulose nanocrystals, cellulose nanofibers, cellulose microfibers, gold or silver nanorods (e.g., 1-20 nanometers in diameter and 10- 100 nm in length), or any combination thereof.

[0070] Aspect 13. The polymer composition of any one of Aspects 1-12, wherein the polymer composition has a modulus of from about 10 kPa to about 100 kPA and/or an adhesion strength of from about 0.05 N/cm ² to about 0.1 N/cm ² , one or both of which can optionally be achieved within about 2 minutes from when the polymer composition is hydrated and the thermoresponsive polymer is at a temperature below the LCST.

[0071] The modulus can be, e.g., from about 10 kPa to about 100 kPa, from about 15 kPa to about 95 kPa, from about 20 kPa to about 90 kPa, from about 30 kPa to about 85 kPa, from about 35 kPa to about 80 kPa, from about 40 kPa to about 75 kPa, from about 45 kPa to about 70 kPa, or from about 50 to about 60 kPa.

[0072] Aspect 14. The polymer composition of any one of Aspects 1-12, wherein the polymer composition has a modulus of from about 10 MPa to about 100 MPa and/or an adhesion strength of from about 8 N/cm ² to about 50 N/cm ² , one or both of which can optionally be achieved within about 2 minutes from when the polymer composition is hydrated and the thermoresponsive polymer is at a temperature above the LCST.

[0073] The modulus can be, e.g., from about 10 kPa to about 100 kPa, from about 15 kPa to about 95 kPa, from about 20 kPa to about 90 kPa, from about 30 kPa to about 85 kPa, from about 35 kPa to about 80 kPa, from about 40 kPa to about 75 kPa, from about 45 kPa to about 70 kPa, or from about 50 to about 60 kPa. The adhesion strength can be, e.g., from about 8 to about 50 N/m ² , from about 10 to about 45 N/m ² , from about 15 to about 40 N/m ² , from about 20 to about 35 N/m ² , or even about 25 N/m ² .

[0074] Aspect 15. The polymer composition of any one of Aspects 1-12, wherein the polymer composition has a modulus of from about 100 MPa to about 5 GPa and/or an adhesion strength of from about 100 N/cm ² to about 1000 N/cm ² , one or both of which can optionally be attained within 2 hours from when the polymer composition is dried and the thermoresponsive polymer is at a temperature above the LCST.

[0075] The modulus can be, e.g., from about 100 MPa to about 5 GPa, or from about 200 MPa to about 4 GPa, or from about 300 MPa to about 3 GPa, or from about 500 MPa to about 2 GPa, or even from about 750 MPa to about 1.2 GPa. The adhesion strength can be from about 100 to about 1000 N/cm ² , from about 200 to about 750 N/cm ² , from about 300 to about 600 N/cm ² , or from about 200 to about 500 N/cm ² .

[0076] Aspect 16. The polymer composition of any one of Aspects 1-15, wherein the polymer composition’s modulus increases through an order of magnitude when the thermoresponsive polymer attains a temperature above the LCST.

[0077] Aspect 17. The polymer composition of any one of Aspects 1-16, wherein the polymer composition’s modulus increases by from 10% to 1000% (e.g., from 10 to 1000%, from 20 to 800%, from 50 to 750 %, from 75 to 500 %, from 100 to 300%) within 5 minutes of the thermoresponsive polymer reaching a temperature above the LCST.

[0078] Aspect 18. The polymer composition of Aspect 17, wherein the polymer composition’s modulus increases by from 10% to 1000% (e.g., from 10 to 1000%, from 20 to 800%, from 50 to 750 %, from 75 to 500 %, from 100 to 300%) within 2 minutes of the thermoresponsive polymer reaching a temperature above the LCST.

[0079] Aspect 19. The polymer composition of any one of Aspects 1-16, wherein the polymer composition’s adhesion strength increases by from 10% to 1000% (e.g., from 10 to 1000%, from 20 to 800%, from 50 to 750 %, from 75 to 500 %, from 100 to 300%) within 5 minutes of the thermoresponsive polymer reaching a temperature above the LCST.

[0080] Aspect 20. The polymer composition of Aspect 19, wherein the polymer composition’s adhesion strength increases by from 10% to 10,000% (e.g., from 10 to 1000%, from 20 to 800%, from 50 to 750 %, from 75 to 500 %, from 100 to 300%) within 2 hours of the thermoresponsive polymer reaching a temperature above the LCST.

[0081] Aspect 21. An article, comprising a polymer composition according to any one of Aspects 1-20 disposed on a substrate.

[0082] Aspect 22. The article of Aspect 21, wherein the substrate is characterized as removable from the polymer composition.

[0083] Aspect 23. An article, the article comprising a polymer composition according to any one of Aspects 1-20 disposed so as to bond two portions of a substrate to one another.

[0084] Aspect 24. An article, the article comprising a polymer composition according to any one of Aspects 1-20 disposed so as to bond two substrates to one another.

[0085] Aspect 25. A kit, the kit comprising an applicator and an amount of a polymer composition according to any one of Aspects 1-20, the applicator configured to controllably dispense the polymer composition. An applicator can be, e.g., a nozzle, a brush, and the like.

[0086] Aspect 26. A method, comprising: effecting heating of a polymer composition according to any one of Aspects 1-20 such that the thermoresponsive polymer attains a temperature above the LCST of the thermoresponsive polymer, or effecting cooling of a polymer composition according to any one of Aspects 1-20 such that the thermoresponsive polymer attains a temperature below the LCST of the thermoresponsive polymer.

[0087] Aspect 27. A method, comprising using a polymer composition according to any one of Aspects 1-20 to bond a first substrate to a second substrate.

[0088] Aspect 28. The method of Aspect 27, further comprising: (a) wetting the polymer composition so as to reduce the modulus of the polymer composition, (b) wetting the polymer composition so as to de-adhere the polymer composition from at least one of the first substrate and the second substrate, (c) cooling the polymer composition so as to reduce the modulus of the polymer composition, (d) cooling the polymer composition so as to de-adhere the polymer composition from at least one of the first substrate and the second substrate, or any combination of (a), (b), (c), or (d).

[0089] Aspect 29. A method, comprising: dispersing a thermoresponsive polymer into a hydrogel precursor, the thermoresponsive polymer being soluble in water, the thermoresponsive polymer having a lower critical solution temperature (LCST), and the thermoresponsive polymer chains being dispersed within the polymeric hydrogel such that when the thermoresponsive polymer attains a temperature above the LCST, the thermoresponsive polymer becomes insoluble and forms physical crosslinks between chains of the polymeric hydrogel.

[0090] Aspect 30. The method of Aspect 29, wherein the method is performed so as to give rise to a polymer composition according to any one of Aspects 1-20.