Preparation of antifouling ultrafiltration membranes by self-organization with amphiphilic materials is a simple and effective method. A series of amphiphilic poly(ethylene glycol)-graft-polyacrylonitrile (PEG-g-PAN) copolymers with various molecular weights of PEGs were synthesized by water-phase precipitation copolymerization using ceric(IV) ammonium nitrate as an initiator. PEG-g-PAN ultrafiltration membranes were fabricated by phase inversion in a wet process. Scanning electron microscopy (SEM) revealed that PEG-g-PAN membranes have the typical asymmetric structure. X-ray photoelectron spectroscopy (XPS) analysis confirmed the enrichment of PEG segments on PEG-g-PAN membrane surfaces. The surface segregation enhances the hydrophilic property and antifouling ability of PEG-g-PAN membranes. All prepared PEG-g-PAN ultrafiltration membranes have lower BSA adsorption, higher flux for protein solution, higher flux recovery ratio, and lower membrane fouling during protein ultrafiltration in comparison with the control PAN membrane. The excellent antifouling property endows PEG-g-PAN membranes with potential applications in protein separation and purification. (C) 2009 Elsevier B.V. All rights reserved.