The blending of a block copolymer into the membrane matrix is a convenient and efficient way to modify membranes. In this study, high-density polyethylene/polyethylene-b-poly(ethylene glycol) (PEG) membranes were prepared via a thermally induced phase separation process, and the extractant effect was investigated. An interesting finding was that the nonpolar extractant (n-hexane) was more conducive to the surface enrichment of the PEG chains than the polar solvent (ethanol). The reason was deemed to be the combined effect of the entropy drive, interfacial energy, and swelling behavior. In addition, the membrane performance related to the surface chemical properties was studied. The results suggest that the prepared blend membranes extracted by n-hexane showed enhanced the hydrophilicity, antifouling properties, and water flux. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3816-3824, 2013