SYNTHESIS OF GRAFT POLYESTERS BY RING-OPENING COPOLYMERIZATION OF EPOXY-TERMINATED POLY(ETHYLENE GLYCOL) WITH ACID ANHYDRIDES

The copolymerization of epoxy-terminated poly (ethylene glycol methyl ether) (CH3PEG-epoxide) with phthalic anhydride catalyzed by tertiary amines was performed in o-dichlorobenzene at 100-degrees-C to prepare the PEG graft polyester. 4-Dimethylaminopyridine was the most favorable catalyst to give the graft polyester with relatively high molecular weight. The acidity of the reaction solution decreased and MBARn of the graft polyesters increased with reaction time. The CH3PEG/phthalic acid ratio of the products was little affected by the kind of solvent and the reaction temperature above 100-degrees-C, but MBARn increased with lowering the polarity of solvents and with raising the temperature. Other acid anhydrides, including maleic, succinic, tetrahydrophthalic, and pyromellitic anhydride, could be copolymerized with CH3PEG-epoxide. The number of branched CH3PEG chains was controlled by the mixing of low molecular weight epoxide such as n-butyl glycidyl ether. CH3PEG component of the graft copolymers melted and crystallized at lower temperature than the raw CH3PEG because of the restriction on the trunk polyester chain.