Controlling the pore size distribution of ultrafiltration membranes is a major challenge. High porosity uniform pore size ultrafiltration membranes could find many applications from virus filtration to protein fractionation. In this work we have modified 500 and 100 kD regenerated cellulose membranes by atom transfer radical polymerization (ATRP).

Polymer chains were grown from the pore surfaces. Importantly no polymer is produced in solution unlike other conventional graft polymerization methods. Being a truly controllable chain growth technique, ATRP enables design and manipulation of the chain MW, which, in turn, allows controlled manipulation of membrane pore size. Surface-initiated ATRP was used to generate polymer brush layers of poly((polyethylene glycol) methacrylate). Membrane characterization was done by ATR-FTIR and contact angle goniometry to follow the modification steps.

Water flux measurements and dextran rejection studies were also conducted. The decrease in water flux correlates well with increased polymerization times, again highlighting the controllable nature of ATRP. Dextran rejection studies also indicate the effects of growing polymer brushes from the surface of the membrane pores.