Branched amphiphilic copolymers with peculiar structural and physicochemical characteristics may find promising application in generating fouling-resistant membrane surface. In this study, novel branched amphiphilic copolymers, P123-b-PEGs, were synthesized by reacting Pluronic P123 with PEG400 using PCl3 as a conjugation reagent, and this novel amphiphilic copolymers were blended with polyethersulfone (PES) to prepare ultrafiltration membranes with superior protein-adsorption-resistant ability. The static water contact angle and X-ray photoelectron spectroscopy revealed the remarkable enrichment of PEO segments at blend membrane surface, as well as the inherent relationship between near-surface coverage and PEO arm number in P123-b-PEG copolymers. Investigations on protein adsorption on blend membranes showed that the protein adsorption amount was significantly decreased. The results of ultrafiltration experiments revealed that the reversible fouling resistance composed the dominated part of total fouling resistance, which endowed the blend membranes containing P123-b-PEG copolymers with higher flux recovery ratio. (c) 2006 Elsevier B.V. All rights reserved.