This research describes a simple approach for attaching poly(ethylene glycol) chains onto the surface of asymmetric ultrafiltration poly(etherimide) (PEI) membranes. Jeffamine (R) M-2070, an amino terminated poly(propylene oxide)/poly(ethylene oxide) block copolymer (PEG-amine) was used as a surface modifying agent. PEI membranes prepared by conventional immersion precipitation were treated in an aqueous solution of PEG-amine and characterized by attenuated total reflectance FTIR, X-ray photoelectron spectroscopy, scanning electron microscopy and tensile tests. The effects of the PEG-amine concentration (2 and 10 wt%), modification time (0.5, 1, 3, and 5 h) and treatment temperature on the morphology, hydrophilicity, permeability, and anti-fouling property of the membrane were investigated. The water contact angle measurement and water absorbance ratio demonstrated that the treatment with PEG-amine for only 0.5 h resulted in a better wettability of the modified PEI membrane. An enlargement of the pore size was observed for the longer reaction times and the higher PEG-amine concentration accounted for a breaking of the PEI chains by over grafting. The best compromise in terms of morphology integrity, rejection and permeability performances, was obtained by using 2 wt% PEG-amine and reaction time lower than 5 h. Based on protein filtration experiments, the anti-fouling properties of the obtained membrane were evaluated, and the results showed a large improvement of resistance to protein fouling for the modified PEI membrane with respect to the unmodified one. (C) 2010 Elsevier B.V. All rights reserved.