Functionalization of polystyrene films by the preferential surface enrichment of surface-modifying macromolecules (SMA4) to achieve a hydrophilic surface with long effective duration is described. The comb-like amphiphilic copolymers (PKG-g-PS) based on styrene-maleic anhydride copolymer (SUA) backbone was synthesized by esterification of SMA with poly(ethylene glycol) (PEG). When PEG-g-PS was melt blended with polystyrene. the preferential surface enrichment of PEG-g-PS was much evident resulting in the large increase of the surface polarity. The effective duration of the surface functionalizatoin was also hugely extended as SMMs were added into the blends. Furthermore, more polyether chain segments on PEG-g-PS could selectively migrate to the surface by the inducement of polar solvent. Compared with the PEG-g-PS/PS and PEG/PEG-g-PS/PS blends, the surface polarity and the effective duration of surface modification both increased greatly when PEG-g-PS was used as the compatibilizer of PEG/PS blends. It was an effective solution to balance the conflict between the duration and efficiency of the surface-modifying additives. (c) 2006 Elsevier B.V. All rights reserved.