A method of forming a rewettable asymmetric membrane comprising: providing a porous substrate having a first major surface, interstitial pores, and a second major surface; applying a polymerizable composition to the first major surface of the porous substrate to provide a coated porous substrate, the polymerizable composition comprising i) at least one polymerizable species having a free-radically polymerizable group selected from a (meth)acryloyl group, an acryloyl group and a vinyl group; ii) at least one copolymer comprising hydrophilic and hydrophobic groups; iii) at least one free radical photoinitiator; and iv) a solvent; exposing the first major surface of the coated porous substrate to a UV radiation source selected from a XeCl excimer lamp having a peak emission at 308 nm, a KrCl excimer lamp having a peak emission at 222 nm, a Xe 2 excimer lamp having a peak emission at 172 nm and a germicidal lamp having a peak emission at 254 nm to polymerize the polymerizable composition in a gradient extending from the first major surface through at least a portion of the thickness of the porous substrate and provide the rewettable asymmetric membrane, and further comprising immersing the rewettable asymmetric membrane in a nonsolvent to precipitate the copolymer onto the portion of the interstitial pores unoccupied by the polymerized material, the membrane comprising a gradient of polymerized material extending from the first major surface to the second major surface with copolymer within portions of the interstitial pores unoccupied by the polymerized material, and wherein the second major surface is substantially free of the polymerized material; and wherein the free radical photoinitiator can selectively absorb radiation from the ultraviolet radiation source. providing a porous substrate having a first major surface, interstitial pores, and a second major surface; applying a polymerizable composition to the first major surface of the porous substrate to provide a coated porous substrate, the polymerizable composition comprising i) at least one polymerizable species having a free-radically polymerizable group selected from a (meth)acryloyl group, an acryloyl group and a vinyl group; ii) at least one copolymer comprising hydrophilic and hydrophobic groups; iii) at least one free radical photoinitiator; and iv) a solvent; i) at least one polymerizable species having a free-radically polymerizable group selected from a (meth)acryloyl group, an acryloyl group and a vinyl group; ii) at least one copolymer comprising hydrophilic and hydrophobic groups; iii) at least one free radical photoinitiator; and iv) a solvent; exposing the first major surface of the coated porous substrate to a UV radiation source selected from a XeCl excimer lamp having a peak emission at 308 nm, a KrCl excimer lamp having a peak emission at 222 nm, a Xe 2 excimer lamp having a peak emission at 172 nm and a germicidal lamp having a peak emission at 254 nm to polymerize the polymerizable composition in a gradient extending from the first major surface through at least a portion of the thickness of the porous substrate and provide the rewettable asymmetric membrane, and further comprising immersing the rewettable asymmetric membrane in a nonsolvent to precipitate the copolymer onto the portion of the interstitial pores unoccupied by the polymerized material, the membrane comprising a gradient of polymerized material extending from the first major surface to the second major surface with copolymer within portions of the interstitial pores unoccupied by the polymerized material, and wherein the second major surface is substantially free of the polymerized material; and wherein the free radical photoinitiator can selectively absorb radiation from the ultraviolet radiation source. <EOS>