Asymmetric ultrafiltration membranes were prepared from blends with synthesized polyacrylonitrile (PAN) and hydrophilically modified polyacrylonitrile (HM-PAN). Two polymers were synthesized through suspension polymerization for PAN and emulsion polymerization for HM-PAN, respectively. Using polymerizable surfactant as a co-monomer, the hydrophilicity and surface activity of HM-PAN was successfully synthesized. The chemical structure and molecular weight of synthesized polymers were characterized by H-1 NMR, FT-IR, and GPC. Surface activity and hydrophilicity were investigated by ATR-IR and XPS, using blend films. And then, the effects of blend composition on the hydrophilicity, morphology, pure water flux, and fouling of asymmetric membranes prepared by phase inversion process were investigated. As HM-PAN was added, the membranes were more hydrophilic, and the top layer of the asymmetric membrane was thicker and pure water flux was decreased, but the molecular weight cut-off was not significantly varied. Fouling of protein particles on the blend membranes was able to reduce as the composition of HM-PAN increases. (C) 2003 Elsevier B.V. All rights reserved.