Imide–aryl ether benzoxazole block copolymers

Abstract

Imide–aryl ether benzoxazole multiblock copolymers were investigated. A key feature of these copolymers is the preparation of bis(amino) aryl ether benzoxazole (PBO) oligomers via nucleophilic aromatic substitution. The molecular weights of the oligomers were 10,500 and 26,000 g/mol with T'gs of 210 and 227°C, respectively. The oligomers were co‐reacted with 4,4′‐oxydianaline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in a N‐methyl‐2‐pyrrolidone/cyclohexanone solvent mixture in the presence of N‐methylmorpholine. The resulting amic ethyl ester‐aryl ether benzoxazoles were isolated and washed to remove homopolymer contamination. Copolymer compositions, determined by 1H‐NMR, ranged from 7 to 54 wt% PBO and the measured compositions were close to those charged. Solutions of the copolymers were cast and cured (350°C) to effect imidization producing clear films. The films showed tough ductile mechanical properties (∼50% elongations) with moduli comparable to PMDA/ODA polyimide. The copolymers displayed good thermal stability with decompositions temperatures in excess of 450°C. Multiphase morphologies were observed irrespective of PBO block lengths or compositions. Good auto‐adhension was achieved in the copolymers containing the high PBO compositions. Copyright © 1990 John Wiley & Sons, Inc.