Imide-Aryl Ether Phenylquinoxaline Block Copolymers

Abstract

Imide-aryl ether phenylquinoxaline block copolymers were prepared and their morphology, mechanical properties, and adhesion characteristics investigated. A key feature of the copolymer synthesis was the preparation of bis(amino) aryl ether phenylquinoxaline oligomers (PQE) via a nucleophilic aromatic substitution reaction. The molecular weights of the oligomers were 6200 and 15 500 with Tg,’s of 230 and 250 °C, respectively. The oligomers were coreacted with 4,4′-oxydianiline (ODA) and pyromeflitic dianhydride (PMDA) diethyl ester diacyl chloride in a N-methylpyrrolidone (NMP) N-cyclohexylpyrrolidone (CHP) solvent mixture in the presence of N-methylmorpholine. The resulting amic ester-aryl ether phenylquinoxaline block copolymers were isolated and given selective solvent rinses, when required, to remove homopolymer contamination. Copolymer compositions, determined by1H NMR, were close to those predicted by the charge. Solutions of the copolymers were cast and cured (350 °C) to effect imidization, affording clear films with elongations ranging from 30 to 120% and moduli between 2000 and 2600 MPa, approximately 5–20% higher than the PMDA/ODA polyimide values. Multiphase morphologies were observed irrespective of the PQE block lengths, and the phase purity increased with PQE weight. Furthermore, the ordered morphology characteristic of the parent polyimide was retained in the polyimide component of the block copolymer. The autoadhesion characteristics (i.e., adhesion of the polyimide to itself) were also investigated, and significant improvements were observed by the incorporation of the PQE block. © 1991, American Chemical Society. All rights reserved.