NOVELTY - Making a functionalized membrane involves providing porous substrate having first major surface, interstitial surfaces and second major surface; applying graftable species to the porous substrate to provide coated porous substrate; and treating the coated substrate with electron beam radiation to provide the functionalized membrane, where the radiation attaches the graftable species to the substrate in a gradient comprising grafted species attached to the substrate, so that concentration of the grafted species is greater at the first major surface than at the second major surface.    USE - For making a functionalized membrane (claimed) useful as filters, breathable articles, absorbent articles and medical articles; in fuel cell; in applications such as water softening, filtration and chromatography.    ADVANTAGE - The functionalized asymmetric membrane with sterilization grade membrane performance is formed. This membrane have a charged gradient of grafted species starting at the first major surface with a larger pore size (e.g. diameter) than the second major surface such that the first major surface faces the feedstock. The upper portion starting at the first major surface of the functionalized asymmetric membrane can function as a prefilter having affinity and size exclusion filtration properties which can provide for longer throughput life, and the smaller pore diameters extending through the thickness of the membrane toward the second major surface can provide size exclusion properties with minimal flux reduction. The smaller pore diameters of the membrane can regulate flux and the gradient of grafted species can be such that the concentration of grafted species is small or zero at the second major surface. The functionalized asymmetric membrane provide for capture and storage of contaminants in the larger diameter pores with less fouling of the smaller diameter pores occurring. The larger concentration of grafted species at the first major surface provides an ultra or nano-filtration membrane for normal flow filtration or tangential flow filtration. The smaller pore diameters provide for easier constriction of the pores.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a functionalized membrane comprising a porous substrate having a first major surface, interstitial surfaces, and a second major surface; and grafted species attached to the porous substrate in a gradient extending through the porous substrate from the first major surface to the second major surface so that a concentration of the grafted species is greater at the first major surface than at the second major surface.