Phenylquinoxaline–Aryl ester block copolymers

Abstract

Phenylquinoxaline–aryl ester block copolymers were synthesized using well‐defined phenolic hydroxyl terminated oligomers via a monomers/oligomer approach. Phenylquinoxaline oligomers with molecular weights of 5600 and 12,900 g/mol were prepared from the condensation of 1,4‐bis(phenylglyoxalyl)benzene and 3,3′‐diaminobenzidine in the presence of 4‐hydroxylbenzil. The oligomers were copolymerized with isophthaloyl chloride and bisphenol A in tetrachloroethane to afford the desired phenylquinoxaline–aryl ester block copolymers. Copolymers with polyester compositions ranging from 15–50 wt % were prepared by controlling the monomers/oligomer stoichiometry. The majority of the materials displayed single phase morphologies with Tgs intermediate to the Tgs for the poly (phenylquinoxaline) and polyester homopolymers. Plots of the reciprocal of the Tg of the copolymers versus composition agreed well with values predicted by the Fox equation. A multiphase morphology was obtained for the copolymer with the highest polyester block length (⋍ 13,000 g/mol), which displayed a Tg at 190 and 300°C indicative of a glassy–glassy system. Significant improvement in the elongations were observed for the copolymers relative to the poly(phenylquinoxaline) homopolymer. The improved elongations were obtained with minimal sacrifice to the modulus. These materials represent the first example of poly(phenylquinoxaline) block copolymers from well‐defined phenylquinoxaline oligomers. Copyright © 1990 John Wiley & Sons, Inc.