Imide-aryl ether phenylquinoxaline random copolymers

Novel imide-aryl ether phenylquinoxaline copolymers were prepared and their morphology and mechanical properties investigated. A key feature of these copolymers is the incorporation of an aryl ether phenylquinoxaline linkage into a semi-rigid polyimide backbone based on 4,4′-oxydianiline (ODA) and pyromellic dianhydride (PMDA) by the use of either 1,4-bis[6-(3-aminophenoxyl)-3-phenyl-2-quinoxalinyl] benzene or 1,4-bis[6-(4-aminophenyoxyl)-3-phenyl-2-quinoxalinyl]benzene as co-diamines. These monomers were prepared by a novel nucleophilic aromatic substitution reaction of 1,4-(6-fluoro-3-phenyl-2-quinoxalinyl) benzene with 4- or 3-aminophenol in the presence of K2CO3. These diamines were used as co-monomers with PMDA and ODA to synthesize poly(amic-acids). Films were cast and cured (350°C) to effect imidization, affording films which showed high elongations and moduli. The copolymers with high phenylquinoxaline compositions displayed Tg values in the 300°C range. The thermal stability of the copolymers was comparable to that of the parent polyimide with decomposition temperatures between 470 and 530°C. The morphology of the copolymers was investigated by dynamic mechanical, wide angle X-ray diffraction (WAXD) and swelling measurements. © 1991.