SELECTIVELY GRAFTED COPOLYMERS AND METHODS OF MAKING THE SAME CROSS-REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/890,701 filed August 23, 2019. The related application is incorporated herein in its entirety by reference. BACKGROUND [0001] A graft copolymer is a polymer comprising a plurality of side chains connected to a polymer backbone, where the side chains and the backbone generally differ in chemical structure. An example of a graft copolymer can be represented by structure (I) where the sequence of C monomer units is referred to as the main chain or backbone, the sequence of D units is the side chain or graft, and X is the unit in the backbone to which the graft is attached. Grafting is an important part of polymer chemistry as it allows for a relatively simple method of modifying polymer properties. [0002] Free-radical polymerization methods are commonly used procedures for the synthesis of graft polymers, where graft copolymers are often prepared by polymerization of a monomer off of a preformed backbone. Conversely, graft copolymers can be prepared by copolymerizing preformed branches onto a preformed backbone. These techniques generally result in a homogenous grafting of the grafts onto the backbone. [0003] There is a need for improved methods of selectively localizing the grafts onto the polymer backbone. BRIEF SUMMARY [0004] Disclosed herein are selectively grafted copolymers and methods of making the same. [0005] In an aspect, a graft copolymer comprises a semi-crystalline base polymer having an amorphous domain and a crystalline domain; wherein the semi-crystalline base polymer comprises an abstractable hydrogen; and a grafted polymer selectively grafted onto the semi-crystalline base polymer in the amorphous domain. [0006] In another aspect, a composition comprises the graft copolymer. [0007] In yet another aspect, a method of forming a graft copolymer comprises forming a mixture comprising a semi-crystalline base polymer, a grafting monomer, and an initiator; wherein the semi-crystalline base polymer comprises an amorphous domain and a crystalline domain. Carbon dioxide is introduced to the mixture in a closed chamber. The grafting monomer is reacted at temperature and pressure conditions above the supercritical point of the carbon dioxide to form a supercritical carbon dioxide, but below a melting temperature of the crystalline domain of the semi-crystalline base polymer to selectively polymerize a plurality of grafts in the amorphous domain thereby forming the graft copolymer. [0008] The above described and other features are exemplified by the following figures, detailed description, and claims. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The following figures are exemplary embodiments, which are provided to illustrate the present disclosure. Several figures are illustrative of the examples, which are not intended to limit devices made in accordance with the disclosure to the materials, conditions, or process parameters set forth herein. [0010] FIG.1A is an illustration of an aspect of the semi-crystalline base polymer prior to grafting signifying crystalline and amorphous regions; [0011] FIG.1B is an illustration of an aspect of a selectively grafted copolymer; [0012] FIG.1C is an illustration of an aspect of a graft copolymer containing two different graft sections; [0013] FIG.2 is a graphical illustration of differential scanning calorimetry thermograms of Examples 1 to 3; [0014] FIG.3 is a graphical illustration of differential scanning calorimetry thermograms of Examples 4 to 5; [0015] FIG.4 is a graphical illustration of differential scanning calorimetry thermograms of Examples 4 and 6 to 8; [0016] FIG.5 is a graphical illustration of the thermal gravimetric analyses of Examples 15, 19, and 20; [0017] FIG.6 is a graphical illustration of the Fourier transform infrared spectra of Examples 15, 16, 19, and 20; [0018] FIG.7 is a graphical illustration of the Fourier transform infrared spectra of Examples 17, 19, and 22; [0019] FIG.8 is a graphical illustration of the Fourier transform infrared spectra of Examples 18, 19, and 23; [0020] FIG.9A is a graphical illustration of the Fourier transform infrared spectra of Examples 24 to 26; [0021] FIG.9B is a graphical illustration of the Fourier transform infrared spectra of Examples 24 to 26; [0022] FIG.10 is a graphical illustration of the Fourier transform infrared spectra of Examples 18, 19, and 27; [0023] FIG.11 is a graphical illustration of differential scanning calorimetry thermograms of Examples 4, 32, and 33; [0024] FIG.12 is a graphical illustration of the Fourier transform infrared spectra of Examples 16 and 32; [0025] FIG.13 is a graphical illustration of differential scanning calorimetry thermograms of Examples 4 and 36; [0026] FIG.14A is a graphical illustration of Fourier transform infrared spectra of Examples 16 and 36; [0027] FIG.14B is a graphical illustration of Fourier transform infrared spectra of Examples 16 and 36; [0028] FIG.15A is a graphical illustration of the differential scanning calorimetry thermograms of Examples 38 and 39; and [0029] FIG.15B is a graphical illustration of the differential scanning calorimetry thermograms of Examples 38 and 39; [0030] FIG.15C is a graphical illustration of the differential scanning calorimetry thermograms of Examples 38 and 39; [0031] FIG.16 is a graphical illustration of the moisture update samples with varying amounts of grafted polystyrene of Example 42; [0032] FIG.17 is a photographic image of the volumetric increase as described in Example 1; and [0033] FIG.18 is a photographic image of the volumetric increase as described in Example 37. DETAILED DESCRIPTION [0034] It has been found that a graft copolymer comprising selectively localized grafts could be formed by grafting on a semi-crystalline base polymer (referred to herein as the base polymer) in supercritical carbon dioxide. Specifically, the graft copolymer can be prepared by forming a mixture comprising the base polymer, a grafting monomer, an optional cosolvent, and an initiator; and introducing carbon dioxide to the mixture in a closed chamber. The grafting monomer can then be reacted at temperature and pressure conditions above the supercritical point of the carbon dioxide to form a supercritical carbon dioxide, but below the melting temperature of the crystalline domain of the base polymer to selectively polymerize a plurality of grafts in the amorphous domain thereby forming the graft copolymer. Utilizing supercritical carbon dioxide as the solvent can dissolve the grafting monomer and can cause swelling of the amorphous domains. This combination of effects can allow for the grafting monomer to easily dissolve into the amorphous domains of the base polymer. Accordingly, the resultant graft copolymer can comprise at least one grafted section and at least one ungrafted section along the base polymer. [0035] It is noted that this concept can be applied to a broad range of base polymers (for example, polyamides and polyesters) with a broad range of graft polymers. The type and amount of the grafted polymers selectively tuned to alter the relative hydrophobic and hydrophilic nature of the resultant graft copolymer. Advantageously, this method of grafting can be used to easily upcycle semi-crystalline polymeric waste in a cost-effective, sustainable way. [0036] FIG.1A is an illustration of a base polymer, b, having two crystalline sections A with an amorphous region B located there between, where the crystalline sections A and the amorphous region B are illustrated in FIG.1B. FIG.1B illustrates that after grafting at temperature and pressure conditions above the supercritical point of the carbon dioxide to form a supercritical carbon dioxide, but below the melting temperature of the crystalline domain A of the base polymer, the graft copolymer comprises a plurality of grafted side chains g in the amorphous region B to form an A-B-A type graft copolymer. FIG.1C illustrates that a second grafting monomer can then be grafted onto the base polymer at a temperature above the melting temperature of the crystalline to form a second plurality of grafted side chains G. The second plurality of grafted side chains can be derived from a different grafting monomer or can have a different average chain length, for example, as determined by comparing the weight average molecular weights of the side chains in the different regions. [0037] It is noted that although an A-B-A type graft copolymer is illustrated in FIG. 1, various other block sequences can be formed, for example, A-B, B-A-B, A-B-A-B-A, or the like. The block sequence can be dictated by at least one of the lamella thickness or degree of crystallinity and the relative length of the blocks can be dictated by the selection of a cosolvent. [0038] The method of making the graft copolymer can comprise forming a mixture comprising a semi-crystalline base polymer, a grafting monomer, and an initiator; wherein the semi-crystalline base polymer comprises an amorphous domain and a crystalline domain; introducing carbon dioxide to the mixture in a closed chamber; and reacting the grafting monomer at temperature and pressure conditions above the supercritical point of the carbon dioxide to form a supercritical carbon dioxide, but below the melting temperature of the crystalline domain of the semi-crystalline base polymer to selectively polymerize a plurality of grafts in the amorphous domain thereby forming the graft copolymer. [0039] The base polymer prior to the grafting polymerization can comprise a polymer having an abstractable hydrogen. As used herein the abstractable hydrogen refers to a hydrogen atom than is removed from the base polymer to form a free radical and wherein the hydrogen is abstractable at a reduced energy due to the presence of at least one of a neighboring carbonyl group –CO– (for example, of a polyketone, a polyurethane, or a polyamide), carboxylate group –CO–O– (for example, of a polyester), oxy group –O– (for example, of a polyacetal), or imino group –NH– (for example, of a polyurethane). During the grafting, the abstractable hydrogen can be removed, thereby forming a graft location. The base polymer can comprise at least one of a polyamide, a polyester (for example, poly(ethylene terephthalate), poly(butylene terephthalate), poly(trimethylene terephthalate)), or poly(lactic acid), a polyketone, a polyacetal (for example, polyoxymethylene), or polyurethane. [0040] The base polymer can comprise a homopolymer or a copolymer. The copolymer can be a block copolymer or a random copolymer. If the base polymer is a copolymer, then the base polymer can comprise a block copolymer having an amorphous domain comprising a plurality of abstractable hydrogens and a crystalline domain different from the amorphous domain. For example, the polymer blocks in the amorphous domain can comprise at least one of a polyamide, a polyester, a polyketone, a polyacetal, or a polyurethane and the polymer blocks in the crystalline domain can comprise a polyolefin (for example, polyethylene or polypropylene). Conversely, the base polymer can be a copolymer comprising two or more different blocks of a polyamide, a polyester, a polyketone, a polyacetal, or a polyurethane. [0041] The mixture can comprise 1 to 80 wt%, or 10 to 70 wt%, or 30 to 50 wt% of the base polymer based on the total weight of the mixture. [0042] The base polymer can have a crystallinity of 5 to 90 wt%, or 10 to 75 wt% based on the total weight of the base copolymer. The base polymer can be in the form of a powder, bead, pellet, or strand, or is an article, for example, a film, a block, or the like. Prior to grafting, the base polymer can be stretched, for example, uniaxially stretched or biaxially stretched. [0043] The grafting monomer can comprise at least one of a non-conjugated diene, a monovinylidene aromatic monomer (for example, styrene, ^-methylstyrene, o-methyl styrene, p-methyl styrene, t-butylstyrene, vinyltoluene, or dichlorostyrene), acrylonitrile, 2- isopropenyl-2-oxazoline, maleic anhydride, a (meth)acrylic acid, a (meth)acrylate monomer, an alkyl (meth)acrylate monomer, N-vinylpyrrolidinone, an olefin, a trialkoxysilane (meth)acrylate, vinyl acetate, a vinyl halide, or a vinyl-terminated siloxane. The grafting monomer can comprise at least one of styrene, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dimethylamino ethyl (meth)acrylate, a glycidyl (meth)acrylate, (meth)acrylamide, or acrylonitrile. The mixture can comprise 10 to 99 wt%, or 30 to 90 wt%, or 50 to 80 wt%, or 40 to 60 wt% of the grafting monomer polymer based on the total weight of the mixture. [0044] The initiator can comprise at least one of acetylcyclohexanesulfonyl peroxide, diacetyl peroxydicarbonate, diethyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di- 2-ethylhexyl peroxydicarbonate, tert-butyl perneodecanoate, 2,2^-azobis(methoxy-2,4- dimethylvaleronitrile), tert-butyl perpivalate, dioctanoyl peroxide, dilauroyl peroxide, 2,2^- azobis(2,4-dimethylvaleronitrile), tert-butylazo-2-cyanobutane, dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate, tert-butyl permaleate, 2,2-azobis(isobutyronitrile), bis(tert- butylperoxy) cyclohexane, tert-butyl peroxyisopropylcarbonate, tert-butyl peroxybenzoate, tert-butyl peracetate, 2,2-bis(tert-butylperoxy) butane, dicumyl peroxide, di-tert-amyl peroxide, di-tert-butyl peroxide, p-methane hydroperoxide, pinane hydroperoxide, cumene hydroperoxide, or tert-butyl hydroperoxide. The initiator can be present in an amount of 0.05 to 1 mole percent (mol%) based on the total number of moles of the grafting monomer. [0045] The mixture can optionally comprise a co-solvent. The co-solvent can be any solvent capable of dissolving the grafting monomer. The co-solvent can comprise at least one of a C _1-4 alkyl alcohol, m-cresol, or dimethyl formamide. Conversely, the mixture can be free of a co-solvent, thereby eliminating any need for a solvent removal step after the grafting. If present, a ratio by volume of the co-solvent to the grafting monomer in the mixture can be 5:1 to 1:5, or 3:1 to 1:3, or 2:1 to 1:2. [0046] The grafting monomer in the mixture can be reacted to form grafts on the amorphous domain of the base polymer. The reacting comprises reacting at temperature and pressure conditions above the supercritical point of the carbon dioxide to form a supercritical carbon dioxide, but below the melting temperature of the crystalline domain of the semi- crystalline base polymer to selectively polymerize a plurality of grafts in the amorphous domain thereby forming the graft copolymer. The reacting can comprise reacting a first grafting monomer at a temperature below the melting temperature of the crystalline domain and then reacting a different second grafting monomer at a temperature above the melting temperature of the crystalline domains. This method can result in blocks of different grafts along the base polymer. [0047] The reacting can comprise at least one of polymerizing via a free radical polymerization, polymerizing via a ring opening metathesis polymerization, or polymerizing via a living free radical polymerization. The reacting can occur at a temperature of 50 to 130 degrees Celsius (°C), or 70 to 100°C. The reacting can occur at a pressure of 7 to 40 megapascal (MPa), or 10 to 35 MPa. The reaction time can be 1 to 80 hours, or 10 to 25 hours. [0048] After reacting, the graft copolymer can be washed or dried, for example, to remove a co-solvent if used or residual grafting monomer. For example, the graft copolymer can be washed with a wash solvent capable of dissolving the grafting monomer and dried at an increased temperature in a vacuum. The wash solvent can comprise at least one of acetone, m-cresol, toluene, or cyclohexane. [0049] A mass of the graft copolymer relative to the base polymer can be increased by greater than 50 wt%, or 50 to 350 wt%. The graft copolymer can have a crystallinity of 5 to 40 wt%, or 5 to 30 wt% based on the total weight of the graft copolymer. The graft copolymer can comprise 10 to 95 wt%, or 20 to 80 wt% of the grafted polymer and 5 to 90 wt%, or 20 to 80 wt% of the semi-crystalline base polymer based on the total weight of the graft copolymer. Depending on the number of amorphous domains in the semi-crystalline base polymer, the graft copolymer can comprise one or more grafted sections and one or more ungrafted sections. [0050] A composition can comprise the graft copolymer. The graft copolymer can be used as a filler, a compatibilizer, an impact modifier, etc. The composition can comprise the graft copolymer and at least one of an additional polymer different from the graft copolymer or an additive. The composition can comprise 1 to 99 wt%, or 5 to 45 wt%, or 50 to 85 wt% of the graft copolymer based on the total weight of the composition. [0051] An article can comprise the composition. The article can be a filter, a membrane, an electrochemical cell (for example, a fuel cell), a consumer product, etc. [0052] The following examples are provided to illustrate the present disclosure. The examples are merely illustrative and are not intended to limit devices made in accordance with the disclosure to the materials, conditions, or process parameters set forth therein. Examples [0053] In the examples, differential scanning calorimetry (DSC) was performed using a TA Instruments Q200 Differential Scanning Calorimeter equipped with RCS90 device for low temperatures. The temperature range was 0 to 250°C, and the heating and cooling rates were 10 degrees Celsius per minute (°C/min). The thermal gravitational analysis (TGA) was performed by placing samples into a platinum pan and heating under nitrogen at a rate of 10°C/min to 700°C using a TA Instruments Q50 Thermogravimetric Analyzer. [0054] The mass fraction of the radically polymerized polymer including the grafted polymer as well as any ungrafted base polymer present was determined using weight and crystallinity analysis, using Equations (1) and (2), respectively. When determined by weight, the mass of the samples before and after grafting was measured and the mass fraction of the grafted material was determined using Equation (1). When determined based on the change in crystallinity, the fractional crystallinity of samples before and after grafting was measured and the mass fraction of the grafted material was determined using Equation (2), where it was assumed that since processing conditions were well-below the melting endotherm of each sample that the crystalline regions remained unmodified. Therefore, the mass fraction of the material that was radically polymerized was determined in accordance with Equations (1) and (2): where mr is the radically polymerized mass fraction of the grafted material, MT and XcT are the total mass and fractional crystallinity of the dried, processed material, and M _i and X _ci are the mass and fractional crystallinity of the sample before grafting. [0055] Fourier Transform Infrared (FTIR) spectra were recorded with a Perkin-Elmer Spectrum One Fourier transform infrared spectrometer directly on unmodified substrates (Examples 16-18, and 26), modified substrates (Examples 32 and 36), residual homopolymer (Examples 19 and 25), and extracted, dried precipitated polymer (Examples 15, 19, 20, 22, 23, 24, and 27). [0056] The materials used in the examples are shown in Table 1. Examples 1-3: Polystyrene grafting onto a polyamide [0057] In Example 2, a polyamide 6 (PA6) powder was placed in a reactor in a solution comprising styrene, the initiator, and a methanol co-solvent. The volume ratio of monomer:co-solvent was 1:1. An initiator concentration of 0.3 mol% relative to the total moles of monomer was used. These relative compositions were used in future examples unless otherwise stated. The reactor was then sealed, heated, and pressurized with carbon dioxide to supercritical conditions, where the pressure was held constant at 28 MPa for 39 hours while the temperature was held at 75°C for 24 hours and then at 115°C for 15 hours. After processing, the reactor was cooled to room temperature and then gradually depressurized to atmospheric conditions. The modified PA6 was then removed, washed in acetone, and vacuum dried at 80°C for at least 12 hours. Larger compositions of polystyrene were generally observed with substrates that were placed at lower height positions in the reactor. Therefore, in Example 3, the process was repeated to incorporate an increased amount of polystyrene onto the PA6 by decreasing the height of powder placement in the reactor. [0058] The samples were then analyzed using DSC, where the resultant curves are shown in FIG.2. The mass increase, the crystallinity, and the mass fractions of polystyrene were determined for each sample and the results are shown in Table 2. The results were compared to the unmodified PA6 powder used in Example 2, and designated Example 1. [0059] Table 2 shows that there was an increase in the mass of the samples after the grafting reaction and that the relative amount of crystallinity decreased after the grafting reaction indicating that more material is present in the amorphous phase. Table 2 also shows that there is good agreement between the Equations of Equation (1) and Equation (2) in determining the mass fraction of polystyrene, indicating that the PA6 crystallinity remained unchanged. [0060] Photographic images of a PA6 tensile bar before (left) and after (right) grafting are shown in FIG.17, where weight percent of PS in the grafted copolymer is 50 wt% and the scale bar is 10 millimeters. Examples 4-8: Grafting of PA6 in a thin film and the effect of varying thickness [0061] In Examples 5-8, PA6 thin films of varying thicknesses were placed in a reactor in a solution comprising styrene, the initiator, and the co-solvent. Polystyrene was grafted onto the PA6 using the procedure of Example 2. The samples were then analyzed using DSC and the resultant curves are shown in FIG.3 and FIG.4. The mass increase, the crystallinity, and the mass fractions of polystyrene were determined for each sample and the results are shown in Table 3, where mm stands for millimeters. The results were compared to the unmodified PA6 film of Example 4. [0062] Table 3 shows that there was an increase in the mass of the samples after the grafting reaction and that there is good agreement between the Equations of Equation (1) and Equation (2) in determining the mass fraction of the polystyrene. The results as shown in Table 3 also illustrate that thin films can be successfully modified. Examples 9-15: Solvent extraction of the grafted PA6 with m-cresol and toluene [0063] Polystyrene was grafted onto various PA6 samples as shown in Table 4 in accordance with Example 2. It was believed that the modified samples comprised the PA6 base polymer, polystyrene grafted onto PA6, and trapped polystyrene homopolymer. Therefore, a solvent extraction method was used to characterize grafting by observing changes in solubility. The modified PA6 was solvated in 1 gram of m-cresol and then mixed with toluene, an antisolvent that is miscible with polystyrene but not PA6. An unmodified PA6 sample was also dissolved in 1 gram of m-cresol. The total mass of each specimen in solution was chosen such that the PA6 concentration in the solvent remained constant at 10 milligrams per gram of m-cresol. Following solvation, 14 grams of toluene were added and mixed with each solution. The samples were then held static for 24 hours and inspected for precipitates. [0064] The mass fraction of polystyrene was determined in accordance with Equation (1) and the results are shown in Table 4, where the weights are shown in milligrams (mg). [0065] Table 4 shows that Examples 12 to 15 that comprised greater than 20 wt% of polystyrene did not precipitate upon toluene addition, indicating that the polystyrene was grafted onto the PA6 due to the apparent change in solubility with large enough concentrations of PS. Examples 16-23: Grafting of polystyrene onto different base polymers [0066] Samples of PA6, PET, and BoPET were placed in a reactor in a solution comprising styrene, the initiator, and methanol co-solvent. Polystyrene was grafted onto the respective polymers in accordance with Example 2 to form the graft copolymer of Examples 20-23. These examples are compared to homopolymers to their respective homopolymers of Examples 16-19. [0067] The modified samples were then solvated in m-cresol and then mixed with cyclohexane, an antisolvent that is miscible with polystyrene but not the base polymer. Specifically, the modified samples were each dissolved in 1 gram of m-cresol followed by adding 14 grams of cyclohexane. For PS/BoPET and BoPET samples of Examples 23 and 18, respectively, 2 grams of m-cresol and 13 grams of cyclohexane were used. Precipitates were repeatedly decanted and washed with cyclohexane 24 hours after the first cyclohexane addition. Precipitates were then vacuum dried at 80°C for 12 hours. [0068] The mass fraction of polystyrene was determined in accordance with Equation (1) and the results are shown in Table 5. [0069] Decanted solutions and purified precipitates of several examples were analyzed using TGA and FTIR, respectively. The TGA and FTIR results of the analyses of the decanted solutions and precipitates of samples containing 34 wt% (Example 20) and 75 wt% (Example 21) of polystyrene modified in PA6 are shown in FIG.5 and FIG.6, respectively, as compared to homopolymers of PS (Example 19) and the unmodified PA6 powder (Example 16). FIG.5 shows that the decants dropped below 0.1 wt% before 100°C, indicating near complete extraction of polystyrene homopolymer. FIG.6 shows the FTIR of PS/PA6 purified precipitates and unmodified homopolymer, where the peaks at 695 inverse centimeters (cm ^-1 ) and 755 cm ^-1 are indicative of monosubstituted benzene from polystyrene and the peak at 3,300 cm ^-1 represents the polyamide 6 secondary amine. Purified precipitates show both polymers indicating that the polystyrene is grafted onto the PA6 as the polystyrene homopolymer was previously extracted. [0070] The precipitates of polystyrene grafted onto PET (Example 22) and onto BoPET (Example 23) were then tested using Fourier transform infrared spectroscopy and the results are shown in FIG.7 and FIG.8, respectively, and are compared to homopolymers of PS (Example 19) and the unmodified base polymer Example 17 and Example 18, respectively. FIG.7 and FIG.8 show the FTIR of purified precipitates and unmodified homopolymer, where the peaks at 695 cm ^-1 and 755 cm ^-1 are indicative of monosubstituted benzene from polystyrene while the peak at 730 cm ^-1 represents the PET carbonyl-substituted aromatic ring. Purified precipitates show both polymers indicating that the polystyrene is grafted onto the PET or BoPET as the polystyrene homopolymer was previously extracted. Examples 24-26: Grafting of poly(methyl methacrylate) onto PET [0071] Samples of PET were placed in a reactor in a solution comprising methyl methacrylate, an initiator, and a co-solvent. Poly(methyl methacrylate) was grafted onto the PET (Example 26) in accordance with Example 2 and compared to homopolymers of poly(methyl methacrylate) (Example 25) and the unmodified PET (Example 24). The modified samples were then solvated in m-cresol and then mixed with acetone, an antisolvent that is miscible with poly(methyl methacrylate) but not the base PET. Specifically, the modified samples were each dissolved in 1 gram of m-cresol followed by adding 13 grams of acetone. Precipitates were repeatedly decanted and washed with cyclohexane 24 hours after the first cyclohexane addition. Precipitates were then vacuum dried at 80°C for 12 hours. [0072] The mass fraction of polystyrene was determined in accordance with Equation (1) and the results are shown in Table 6. [0073] The precipitates of Example 26 containing poly(methyl methacrylate) (PMMA) grafted onto PET was then tested using Fourier transform infrared spectroscopy and the results are shown in FIG.9A and FIG.9B as compared to homopolymers of poly(methyl methacrylate) (Example 25) and the unmodified PET (Example 24). In FIG.9B, the peak at 730 cm ^-1 represents the PET carbonyl-substituted aromatic ring while the peak in FIG.9A at 1,725 cm ^-1 represents the PMMA acrylate carboxyl. Peaks at 1,630 cm ^-1 and 3,400 cm ^-1 represent hydroxyl groups. Purified precipitate of Example 26 shows both polymers indicating that the poly(methyl methacrylate) is grafted onto the PET as the poly(methyl methacrylate) homopolymer was previously extracted. Example 27: Grafting of polystyrene onto BoPET without co-solvent [0074] BoPET was placed in a reactor in a solution comprising styrene and the initiator. No cosolvent was used. Polystyrene was grafted onto the BoPET in accordance with Example 2. The mass fraction of the grafted polystyrene was determined in accordance with Equation (1) to be 35%. [0075] Polystyrene homopolymer was extracted from the modified sample using m- cresol and cyclohexane similar to procedures outlined in Examples 18 and 23. The precipitate was analyzed using FTIR whose results are shown in FIG.10, where the peaks at 695 cm ^-1 and 755 cm ^-1 are indicative of monosubstituted benzene from polystyrene while the peak at 723 cm ^-1 represents the PET carbonyl-substituted aromatic ring. Purified precipitates show both polymers indicating that the polystyrene is grafted onto the BoPET as the polystyrene homopolymer was previously extracted. [0076] Example 27 shows that polystyrene can be grafted onto BoPET without a co- solvent. Example 28-31: Grafting poly(hydroxyethyl methacrylate) onto PA6 [0077] Four 1 mm thick samples of PA6 were placed in a reactor in a solution comprising hydroxyethyl methacrylate, the initiator, and a methanol co-solvent. Poly(hydroxyethyl methacrylate) was grafted onto the PA6 in accordance with Example 2. [0078] The mass fraction of the grafted poly(hydroxyethyl methacrylate) was determined in accordance with Equation (1) and the results are shown in Table 7. Example 32-35: Grafting of poly(vinyl acetate) onto PA6 [0079] Four 1 mm thick samples of PA6 were placed in a reactor in a solution comprising vinyl acetate, the initiator, and methanol co-solvent. Poly(vinyl acetate) was grafted onto the PA6 in accordance with Example 2. Examples 32 and 33 were then analyzed using DSC and the resultant curves are shown in FIG.11. [0080] The mass fraction of the grafted poly(vinyl acetate) was determined in accordance with Equation (1) and (2) and the results are shown in Table 8. [0081] There is some disagreement with Equations (1) and (2) for Examples 32 and 33. Without wishing to be bound by theory, it is believed that this discrepancy can be attributed to the low incorporations of poly(vinyl acetate) and the variability in integration limits when determining crystallinity for Equation (2). [0082] FTIR was performed on Example 32, whose results are shown in FIG.12 and compared with unmodified polyamide 6 (Example 16). The peak at 1,740 cm ^-1 is indicative of the acetate carbonyl from poly(vinyl acetate). Example 36: Grafting poly(2-acrylamido-2-methylpropane sulfonic acid) onto PA6 [0083] A 0.5 mm thick sample of PA6 was placed in a reactor in a solution comprising of 2-acrylamido-2-methylpropane sulfonic acid, the initiator, and a co-solvent comprising DMF and methanol. The volume ratio of monomer:DMF:methanol was 1:1:2. Poly(2-acrylamido-2-methylpropane sulfonic acid) was grafted onto the PA6 in accordance with Example 2. [0084] The sample was then analyzed using DSC whose resultant curves are shown in FIG.13 along with the resultant DSC curves of the unmodified PA6 film of Example 4. The mass fraction of grafted poly(2-acrylamido-2-methylpropane sulfonic acid) was determined in accordance with Equation (1) and Equation (2) and the results are shown in Table 9. [0085] Similar to above, it is believed that the discrepancy in the mass fractions as determined in accordance with Equations (1) and (2) can be attributed to the low incorporations of the grafting polymer and the variability in integration limits when determining crystallinity for Equation (2). [0086] FTIR was performed on the modified specimen whose results are shown in FIG.14A and FIG.14B) along with FTIR results of the unmodified PA6 powder (Example 16). The peaks at 1,038 cm ^-1 and 1,200 cm ^-1 are indicative of the SO2 group asymmetric stretching from the poly(2-acrylamido-2-methylpropane sulfonic acid). Example 37: Polystyrene grafting onto isotactic polypropylene [0087] An isotactic polypropylene film was placed in a reactor in a solution comprising styrene and a tert-butyl peroxybenzoate initiator. A co-solvent was not present. An initiator concentration of 0.3 mol% relative to the total moles of monomer was used. The reactor was then sealed, heated, and pressurized with carbon dioxide to supercritical conditions, where the pressure was 28 MPa and the temperature was held at 75°C for 24 hours and then at 115°C for 15 hours. After processing, the reactor was cooled to room temperature and then gradually depressurized to atmospheric conditions. The modified iPP was then removed, washed in toluene, then acetone, and vacuum dried at 80°C for 16 hours. A mass increase of 109% of the modified iPP relative to the initial iPP film was observed indicating that the modified iPP contained 52 wt% of the polystyrene. [0088] Purification and extraction of the polystyrene homopolymer present in the modified iPP film was performed in order to determine the graft yield. The modified iPP was solvated in p-xylene at a concentration of approximately 25 mg of iPP/g of p-xylene, and then mixed with excess cyclohexane, an antisolvent that is miscible with polystyrene but not iPP. The precipitate was repeatedly decanted and washed with cyclohexane 24 hours after the first cyclohexane addition. The purified precipitate was then vacuum dried at 80°C for 16 hours. [0089] FTIR analysis was performed on the modified iPP before and after the extraction. The presence of a polystyrene peak in the extracted sample indicates that some grafting occurred. Using Equation (2), the mass fraction of the polystyrene before and after extraction was determined to be 55 wt% and 5.5 wt%, respectively. Due to recrystallization of the precipitate from solution, the second heating scans from DSC were used for Equation (2) calculations such that recrystallization for specimens before and after extraction were subjected to the same thermal history. The graft yield, G (mass fraction of PS after extraction divided by the mass fraction of PS before extraction times 100), was then calculated and is shown in Table 10. [0090] The above quantifications assumed that the crystallinity of the ungrafted regions, when cooled from the molten state, were unaffected by the presence or absence of polystyrene homopolymer. Henceforth, ¹³ C Solid-State NMR was performed on the extracted precipitates as another method to determine the composition of grafted polymer and consequently, G. When calculated, the mass fraction of PS determined by NMR was divided by the mass fraction of PS from Equation (1). The graft yield of Example 37 was compared to the graft yield of Example 20 and Example 27. In Example 37, direct polarization was used for quantitative validity. For Examples 20 and 27, cross polarization was used given the similarities in segmental mobility of each block and integrations of peaks corresponding to only CH and CH ₂ carbons. [0091] The graft yields for Examples 20, 27, and 37 from both DSC and NMR are reported in Table 10. The 112 % yield calculated in Example 20 from NMR can be explained by possible product loss during processing given the powdered form of this material. Product loss during processing would have lowered the measured M _T and thus m _r from Equation (1), consequently overestimating G. Though yields calculated by NMR are higher than that of DSC for all examples, both techniques demonstrate that the graft yields for Examples 20 and 27 are significantly higher than that obtained using polypropylene as a base polymer. It is believed that the presence of the abstractable hydrogen increases the grafting efficiency by reducing the activation energy for the initial grafting reaction, resulting in a higher number of initial grafting sites and ultimately resulting in an increased graft yield. [0092] Photographic images of an iPP film before (top) and after (bottom) grafting are shown in FIG.18, where weight percent of PS in the grafted copolymer is 52 wt% and the scale bar is 10 millimeters. Examples 38-39: Effect of grafted PS on crystallization and glass transition temperature [0093] DSC scans were performed on two PS grafted PA6 polymers and the results are shown in FIG.15A-C. Example 38 contained 34 wt% PS and Example 39 contained 75 wt% PS before purification. FIG.15A shows the first cooling and heating scans of Examples 38 and 39. Analyzing the cooling and heating curves of Example 38 it is found that the sum of the first and second crystallization exotherms (20 J/g of c1 and 21 J/g of c2) is equal to the heating endotherm (41 J/g). Likewise, for Example 39, the sum of the first and second crystallization exotherms (0 J/g of c1 and 17 J/g of c2) is approximately equal to the heating endotherm (18 J/g). This data shows that these graft copolymers can be melted and recrystallized to the same fraction as the non-melted material. It is noted that the additional lower temperature crystallization exotherm at approximately 70°C is likely an indication of possible frustration from the polystyrene grafts. [0094] FIG.15B shows the melting endotherms during the first and second heating cycles. In FIG.15B, the crystallinity measured by the first and second scans for Example 38 was 19 wt% and 18 wt%, respectively, and the crystallinity measured by the first and second scans for Example 39 was 7 wt% and 8 wt%, respectively. This data illustrates that the PA6 can recrystallize to the same fraction after melting. [0095] FIG.15C shows the glass transition temperatures of Examples 38 and 39 as measured from the first and second scans. This data illustrates that the glass transition temperature of the graft copolymer is increased significantly, by about 40°C, relative to the virgin PA6 and showed no composition dependence on the PS at the graft amounts measured. Examples 40-41: Effect of polymerization conditions on the resultant graft copolymer [0096] Two graft copolymers of PS grafted onto PA6 were prepared using identical grafting conditions except that the polymerization temperature of Example 40 was 115°C and the polymerization temperature of Example 41 was 130°C. After the grafting, the PA6 was degraded by hydrolyzing with superheated water and the remaining PS was dissolved in chloroform and the polystyrene was then characterized independently by solution NMR. Molecular weight control was demonstrated using end group analyses and compared to the theoretical molecular weight as calculated from the Arrhenius Equation. The results in number average molecular weight (X _n ) are shown in Table 11. [0097] Table 11 shows that increasing the polymerization temperature resulted in the expected decrease in the molecular weight. Example 42: Moisture update of PS grafted PA6 copolymers. [0098] Graft copolymers including 0 wt%, 20 wt%, 40 wt%, 60 wt%, and 72 wt% of PS grafted onto PA6 were prepared by grafting the PS onto 1 mm thick thin films of the PA6. The moisture uptake with time of the samples at 70°C and a relative humidity of 76% was measured and the results are shown in FIG.16. FIG.16 shows that increasing the amount of the PS resulted in an increase in the hydrophobicity of the samples as indicated by a reduction in the equilibrium moisture uptake. Example 43: Moisture uptake of a hydrophilically modified PA6 copolymer [0099] Di(ethylene glycol) methyl ether methacrylate was grafted onto a PA6 polymer and was swelled in water at room temperature (about 23°C) for 15 hours. The swollen graft copolymer had a mass increase of 20% (volume increase of 19%) as compared to an ungrafted PA6 film that had a mas increase of only 5 wt% (volume increase of 3%). These results show that the presence of the hydrophilic graft significantly increased the swelling ability of the graft copolymer, resulting in a mass increase which was 300% greater than unmodified PA6. Thus, a range of properties are accessible by altering the monomer used in this process. [0100] Set forth below are non-limiting aspects of the present disclosure. [0101] Aspect 1: A graft copolymer comprising: a semi-crystalline base polymer having an amorphous domain and a crystalline domain; and a grafted polymer selectively grafted onto the semi-crystalline base polymer in the amorphous domain. [0102] Aspect 2: The graft copolymer of Aspect 1, wherein the semi-crystalline base polymer comprises an abstractable hydrogen. [0103] Aspect 3: The graft copolymer of any one or more of the preceding aspects, wherein the semi-crystalline base polymer comprises at least one of a polyamide, a polyester (for example, poly(ethylene terephthalate), poly(butylene terephthalate), poly(trimethylene terephthalate)), poly(lacticacid), a polyketone, a polyacetal (for example, (polyoxymethylene)), or polyurethane. The semi-crystalline base polymer can comprise at least one of a polyamide or a polyester. [0104] Aspect 4: The graft copolymer of any one or more of the preceding aspects, wherein the semi-crystalline base polymer comprises at least two different blocks of different repeat units; wherein at least one block forms the amorphous domain and a different block forms the crystalline domain. [0105] Aspect 5: The graft copolymer of any one or more of the preceding aspects, wherein the grafted polymer is derived from at least one of an olefin, a non-conjugated diene, a monovinylidene aromatic monomer (for example, styrene, ^-methylstyrene, o-methyl styrene, p-methyl styrene, t-butylstyrene, vinyltoluene, or dichlorostyrene), methacrylic acid, an alkyl (meth)acrylate monomer, a trialkoxysilane (meth)acrylate, acrylonitrile, vinyl acetate, N-vinylpyrrolidinone, 2-isopropenyl-2-oxazoline, a vinyl halide, or a vinyl- terminated siloxane. [0106] Aspect 6: The graft copolymer of any one or more of the preceding aspects, wherein the graft copolymer has a crystallinity of 5 to 40 wt%, or 5 to 30 wt% based on the total weight of the graft copolymer. [0107] Aspect 7: The graft copolymer of any one or more of the preceding aspects, wherein the graft copolymer comprises 10 to 95 wt%, or 20 to 80 wt% of the grafted polymer and 5 to 90 wt%, or 20 to 80 wt% of the semi-crystalline base polymer based on the total weight of the graft copolymer. [0108] Aspect 8: A composition comprising the graft copolymer of any one or more of the preceding aspects. [0109] Aspect 9: The composition of Aspect 8, wherein the composition further comprises at least one of a polymer different from the graft copolymer or an additive. [0110] Aspect 10: A method of forming a graft copolymer, for example, of any one or more of the preceding aspects comprising: forming a mixture comprising a semi- crystalline base polymer, a grafting monomer, and an initiator; wherein the semi-crystalline base polymer comprises an amorphous domain and a crystalline domain; introducing carbon dioxide to the mixture in a closed chamber; and reacting the grafting monomer at temperature and pressure conditions above the supercritical point of the carbon dioxide to form a supercritical carbon dioxide, but below a melting temperature of the crystalline domain of the semi-crystalline base polymer to selectively polymerize a plurality of grafts in the amorphous domain thereby forming the graft copolymer. [0111] Aspect 11: The method of Aspect 10, wherein the mixture further comprises a co-solvent capable of dissolving the grafting monomer. [0112] Aspect 12: The method of Aspect 11, wherein the co-solvent comprises at least one of a C _1-4 alkyl alcohol, acetone, or dimethyl formamide. [0113] Aspect 13: The method of any one or more of Aspects 10 to 12, wherein the reacting comprises at least one of free radical polymerization, ring opening metathesis polymerization, or living free radical polymerization. [0114] Aspect 14: The method of any one or more of Aspects 10 to 13, wherein the semi-crystalline polymer is in the form of a powder or is an article. [0115] Aspect 15: The method of Aspect 14, wherein the semi-crystalline polymer is in the form of a uniaxially or biaxially stretched film. [0116] Aspect 16: The method of any one or more of Aspects 10 to 15, wherein the initiator comprises at least one of acetylcyclohexanesulfonyl peroxide, diacetyl peroxydicarbonate, diethyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-2- ethylhexyl peroxydicarbonate, tert-butyl perneodecanoate, 2,2^-azobis(methoxy-2,4- dimethylvaleronitrile), tert-butyl perpivalate, dioctanoyl peroxide, dilauroyl peroxide, 2,2^- azobis(2,4-dimethylvaleronitrile), tert-butylazo-2-cyanobutane, dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate, tert-butyl permaleate, 2,2 -azobis(isobutyronitrile), bis(tert- butylperoxy) cyclohexane, tert-butyl peroxyisopropylcarbonate, tert-butyl peroxybenzoate, tert-butyl peracetate, 2,2-bis(tert-butylperoxy) butane, dicumyl peroxide, di-tert-amyl peroxide, di-tert-butyl peroxide, p-methane hydroperoxide, pinane hydroperoxide, cumene hydroperoxide, or tert-butyl hydroperoxide. [0117] Aspect 17: The method of any one or more of Aspects 10 to 16, further comprising removing a residual grafting monomer from the graft copolymer, optionally by washing or drying the graft copolymer. [0118] Aspect 18: The method of any one or more of Aspects 10 to 17, further comprising reacting a second grafting monomer at temperature and pressure conditions above the supercritical point of the carbon dioxide to form the supercritical carbon dioxide and above the melting temperature of the crystalline domain of the semi-crystalline base polymer. [0119] Aspect 19: The method of any one or more of Aspect 10 to 18, wherein a ratio by volume of the co-solvent to the grafting monomer in the mixture is 5:1 to 1:5, 3:1 to 1:3, or 2:1 to 1:2. [0120] Aspect 20: The method of any one or more of Aspect 10 to 19, wherein the initiator is present in an amount of 0.05 to 1 mol% based on the total number of moles of the grafting monomer. [0121] Aspect 21: The method of any one or more of Aspect 10 to 20, wherein the mixture comprises 10 to 99 wt% of the grafting monomer polymer based on the total weight of the mixture. [0122] Aspect 22: The method of any one or more of Aspect 10 to 21, where the mixture comprises 1 to 80 wt% of the semi-crystalline base polymer based on the total weight of the mixture. [0123] Aspect 23: The method of any one or more of Aspects 10 to 22, wherein the graft copolymer is any one or more of the graft copolymer of Aspects 1 to 7. [0124] The compositions, methods, and articles can alternatively comprise, consist of, or consist essentially of, any appropriate materials, steps, or components herein disclosed. The compositions, methods, and articles can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any materials (or species), steps, or components, that are otherwise not necessary to the achievement of the function or objectives of the compositions, methods, and articles. [0125] The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term “or” means “and/or” unless clearly indicated otherwise by context. Reference throughout the specification to “an aspect”, “an embodiment”, “another embodiment”, “some embodiments”, and so forth, means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments. [0126] The endpoints of all ranges directed to the same component or property are inclusive of the endpoints, are independently combinable, and include all intermediate points and ranges. For example, ranges of “up to 25 wt%, or 5 to 20 wt%” is inclusive of the endpoints and all intermediate values of the ranges of “5 to 25 wt%,” such as 10 to 23 wt%, etc. [0127] The term “at least one of” means that the list is inclusive of each element individually, as well as combinations of two or more elements of the list, and combinations of at least one element of the list with like elements not named. Also, the term “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like. Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs. [0128] Compounds are described using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency filled by a bond as indicated, or a hydrogen atom. A dash ( -") that is not between two letters or symbols is used to indicate a point of attachment for a substituent. For example, -CHO is attached through carbon of the carbonyl group. As used herein, the term “(meth)” for example, in the term “(meth)acryl” encompasses scenarios where the methyl group is present and when it is not, for example, it encompasses both acryl and methacryl groups. [0129] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference. [0130] While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.