Abstract
Novel imide-aryl ether phenylquinoxaline copolymers were prepared and their morphology and thermal properties investigated. A key feature of these copolymers is the incorporation of an aryl ether phenylquinoxaline linkage into a semi-rigid polyimide backbone based in pyromellitic dianhydride (PMDA) with 4,4′-oxydianiline (ODA) and either 2,3-bis-[(3-aminophenoxy)phenyl]quinoxaline or 2,3-bis-[(4-aminophenoxy)phenyl]quinoxaline as co-diamines. These monomers were prepared by a novel nucleophilic aromatic substitution reaction of 2,3-bis(4-fluorophenyl)quinoxaline 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) which were cast and cured (350°C) to effect imidization, affording tough films. The copolymers with high phenylquinoxaline compositions displayed glass transition temperature values in the 300°C range. The thermal stability of the copolymers was comparable to that of the parent polyimide, with decomposition temperatures between 455 and 480°C. The morphology of the copolymers was investigated by dynamic mechanical thermal analysis and wide angle X-ray diffraction. © 1997 Elsevier Science Ltd. All rights reserved.