Blending the block copolymer into the membrane matrix is a convenient and efficient way for membrane modification. In this study, HDPE/PE-b-PEG membranes were prepared via TIPS process, and the extractant effect was investigated. An interesting finding was that a non-polar extractant (n-hexane) was more conducive to the surface enrichment of PEG chains than a polar solvent (ethanol). The reason was deemed to be the combined effect of entropy drive, interfacial energy, and the swelling behavior. Besides, membrane performances related to the surface chemical properties were studied. Results suggested that the prepared blend membranes extracted by n-hexane showed enhanced hydrophilicity, anti-fouling property and water flux. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2680-2687, 2013