TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The ionic group is a sulfonic acid or its salt, amine or quaternary ammonium salt. The nucleophilic compound comprises a nucleophilic group selected from a primary amino group, a secondary amino group, a hydroxyl group and/or a carboxyl group. The graftable species is selected from a glycidyl (meth)acrylate, an isocyanatoalkyl (meth)acrylate and/or vinyl azlactone.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The porous substrate is hydrophilic or hydrophobic; and is selected from a film, a non-woven web and/or a woven web. The porous substrate comprises a microporous, thermally-induced phase separation membrane comprising poly(vinylidene fluoride); or nylon. The first major surface of the functionalized membrane is hydrophilic, and the second major surface of the functionalized membrane is hydrophobic. The at least one graftable species comprises a free-radically polymerizable group and an additional functional group selected from an ethylenically unsaturated group, an epoxy group, an azlactone group, an ionic group and/or an alkylene oxide group. The additional functional group reacts with a nucleophilic compound. The at least one graftable species comprises a functionality of at least 2. The graftable species is a polyalkylene glycol di(meth)acrylate. Preferred Method: The method further involves positioning the coated porous substrate between a first layer and a second layer to form a multilayer structure, the first layer positioned adjacent to the first major surface and the second layer positioned adjacent to the second major surface, and where treating the coated porous substrate with electron beam radiation involves exposing the multilayer structure to the electron beam radiation; removing the first layer and the second layer from the multilayer structure after treating the coated porous substrate with electron beam radiation; positioning a first layer on the coated porous substrate adjacent to the first major surface to form a bilayer structure, and where exposing the coated porous substrate to electron beam radiation; removing the first layer from the bilayer structure after treating the coated porous substrate with electron beam radiation; and treating the coated porous substrate with an inert atmosphere to provide the functionalized membrane. A dose of electron beam radiation delivered to the coated porous substrate is 0-120 kGy. The electron beam radiation is operated at a voltage of 120-250 keV. A portion of the grafted species forms a gel. The step of applying at least one graftable species to the porous substrate involves applying two graftable species to the porous substrate at the same time or sequentially to the porous substrate, a first graftable species is applied to the porous substrate to provide the coated porous substrate and a second graftable species is applied to the coated porous substrate prior to treating the coated porous substrate with electron beam radiation. The method further involves applying at least one additional graftable species to the functionalized membrane and thereafter treating the functionalized membrane with a second treatment of electron beam radiation to attach the additional graftable species to the functionalized membrane, the functionalized membrane having at least one additional grafted species. The concentration of the at least one additional grafted species is greater at the second major surface than at the first major surface. The porous substrate is treated with electron beam radiation optionally prior to applying step. Preferred Membrane: The porous substrate is optionally asymmetric. An average pore diameter of the first major surface is optionally greater than an average pore diameter of the second major surface.