Synthesis and characterization of amphiphilic graft copolymers based on poly(styrene-co-maleic anhydride) with oligo(oxyethylene) side chains and their GPC behavior

A series of amphiphilic graft copolymers were synthesized based on poly(sty rene-co-maleic anhydride) (SMAs) (backbone copolymers) and methoxypolyethyl ene glycols (MPEGs) (grafts) in this study. Selection of proper reaction co nditions using p-toluenesulfonic acid (PTSA) as catalyst and toluene as sol vent in the present research can prevent crosslinking reactions which may o ccur due to the presence of di-functional polyethylene glycol in the commer cial MPEGs. The structures and compositions of the graft copolymers were de termined by gel permeation chromatography (GPC) and H-1 NMR analysis. It is noteworthy that the GPC behavior of these graft copolymers follows the rul e of thumb for GPC, i.e. the higher molecular weight copolymers have lower retention volumes. This is very different from the GPC behavior of similar graft copolymers reported previously in the literature. Also, differential scanning calorimetry (DSC) characterization shows that there are two transi tion temperatures for some of these amphiphilic copolymers owing to the exi stence of another aggregation phase of MPEG grafts. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.