Abstract: The present paper covers the poly (ethylene oxide) macromer with vinyl benzyl terminal group (PEO-VB) prepared by deactivation of the alkoxide function of mono-functional "living" PEOchains with vinyl benzyl chloride (VBC). The obtained macromers were subjected to careful purification and detailed characterization. Anew kind of amphiphilic polystyrene-g-poly(ethylene oxide) (PS-g-PEO) with both mi-crophase separated and PEO side chains was synthesized from radical copolymerization of PEO-VB macromer with styrene monomer. An improved purification method, referred as "selective dissolvation", was established for the isolation of graft copolymers from the grafting products, and the purity and yield of the purified copolymers were satisfactory. The well-defined structure of the purified copolymers was confirmed by IR, ¹H NMR and GPC. The bulk composition of the graft copolymers was determined by a well-established first derivative UVspectrometry. Various experimental parameters controlling the copolymerization were also studied. The results indicate that the feed ratio of macromer to styrene (M/S) was the most important factor in determining the composition of the copolymers. Thus a series of PS-g-PEO with a wide range of bulk compositions were obtained simply by adjusting the value of M/S. As clearly indicated by transmission electron microscopy, this amphiphilic graft copolymers may readily form microphase separated structures.

Key words: Poly(ethyiene oxide) macromer, Polystyrene-g-poly(ethylene oxide), Pu-rification of graft copolymer, Amphiphilic and microphase separated structure, Biocom-patible polymer