A polymer composition comprising: a polymer matrix comprising a polyolefin; and one or more polymer particles dispersed in the polymer matrix, wherein the one or more polymer particles comprise a polar polymer selectively crosslinked with a crosslinking agent in the presence of the polymer matrix to generate particles containing intraparticle covalent linkages between the polar polymer chains, thereby maintaining the polymer matrix intact, wherein: the one or more polymer particles have an average particle size of up to 200 μm, the polar polymer is selected from the group consisting of polyvinyl alcohol, ethylene vinyl alcohol copolymer, ethylene vinyl acetate copolymer and mixtures thereof, the polymer matrix further comprises a compatibilizing agent including a functionalized polyolefin configured to modify interactions between the polyolefin of the polymer matrix and the polar polymer, and the functionalized polyolefin is functionalized with maleic anhydride, maleic acid, acrylic acid, methacrylic acid, itaconic acid, itaconic anhydride, methacrylate, acrylate, epoxy, silane, succinic acid, succinic anhydride, ionomers, or mixtures thereof; wherein the polyolefin is present in a range of from 30 wt% to 99.9 wt%, the polar polymer in a range of from 0.1 wt% to 70 wt%, and the functionalized polyolefin in a range of from 0.1 wt% to 15 wt%, wherein the percents by weight are expressed by weight of the total polymer composition; and wherein selectively crosslinking the polar polymer comprises adding the crosslinking agent to a polymer blend at a percent by weight of the polymer blend of from 0.001 wt% to 10 wt%, wherein the polymer blend comprises the polymer matrix and the polar polymer. a polymer matrix comprising a polyolefin; and one or more polymer particles dispersed in the polymer matrix, wherein the one or more polymer particles comprise a polar polymer selectively crosslinked with a crosslinking agent in the presence of the polymer matrix to generate particles containing intraparticle covalent linkages between the polar polymer chains, thereby maintaining the polymer matrix intact, wherein: the one or more polymer particles have an average particle size of up to 200 μm, the polar polymer is selected from the group consisting of polyvinyl alcohol, ethylene vinyl alcohol copolymer, ethylene vinyl acetate copolymer and mixtures thereof, the polymer matrix further comprises a compatibilizing agent including a functionalized polyolefin configured to modify interactions between the polyolefin of the polymer matrix and the polar polymer, and the functionalized polyolefin is functionalized with maleic anhydride, maleic acid, acrylic acid, methacrylic acid, itaconic acid, itaconic anhydride, methacrylate, acrylate, epoxy, silane, succinic acid, succinic anhydride, ionomers, or mixtures thereof; wherein the polyolefin is present in a range of from 30 wt% to 99.9 wt%, the polar polymer in a range of from 0.1 wt% to 70 wt%, and the functionalized polyolefin in a range of from 0.1 wt% to 15 wt%, wherein the percents by weight are expressed by weight of the total polymer composition; and wherein selectively crosslinking the polar polymer comprises adding the crosslinking agent to a polymer blend at a percent by weight of the polymer blend of from 0.001 wt% to 10 wt%, wherein the polymer blend comprises the polymer matrix and the polar polymer. the one or more polymer particles have an average particle size of up to 200 μm, the polar polymer is selected from the group consisting of polyvinyl alcohol, ethylene vinyl alcohol copolymer, ethylene vinyl acetate copolymer and mixtures thereof, the polymer matrix further comprises a compatibilizing agent including a functionalized polyolefin configured to modify interactions between the polyolefin of the polymer matrix and the polar polymer, and the functionalized polyolefin is functionalized with maleic anhydride, maleic acid, acrylic acid, methacrylic acid, itaconic acid, itaconic anhydride, methacrylate, acrylate, epoxy, silane, succinic acid, succinic anhydride, ionomers, or mixtures thereof; wherein the polyolefin is present in a range of from 30 wt% to 99.9 wt%, the polar polymer in a range of from 0.1 wt% to 70 wt%, and the functionalized polyolefin in a range of from 0.1 wt% to 15 wt%, wherein the percents by weight are expressed by weight of the total polymer composition; and wherein selectively crosslinking the polar polymer comprises adding the crosslinking agent to a polymer blend at a percent by weight of the polymer blend of from 0.001 wt% to 10 wt%, wherein the polymer blend comprises the polymer matrix and the polar polymer.