Protein separation by ion-exchange chromatography remains a focus for many researchers working in the field of bioseparations. When used as chromatography media in filtration module, synthetic microporous or macroporous membranes offer advantages over resin-based media, such as low pressure drop, high production rate, and facile scale up and set up. The objective of this research was to surface modify commercially available regenerated cellulose membrane by atom transfer radical polymerization to produce high-capacity ion-exchange membranes for protein chromatography. The monomer 2-dimethylaminoethyl methacrylate was polymerized from cellulose membranes to convert them into ion-exchange membranes. Physicochemical properties and performance properties were studied as a function of polymerization time with various analytical measurement techniques; these include average membrane pore size, pore-size distributions, membrane surface chemistry, and ion-exchange capacities. Protein adsorption experiments were done with an Atka purifier to evaluate dynamic capacities of our surface modified membranes.