Degradation of poly(p-phenylene benzobisthiazole) (PBT) rigid rod, poly(ether ether ketone ether ketone) (PEEKEK) semi-flexible coil, and a grafted “hairy rod” polymer containing PBT and PEEKEK

Abstract

Thermal degradation pathways of the rigid-rod polymer, poly (p-phenylene benzobisthiazole, PBT) have been elucidated by thermal volatilization analysis and related techniques. Processes are characterized by the expulsion of hydrogen sulphide, acetylene, and some carbon disulphide. Evidence is presented for the production and subsequent polymerization of aromatic nitriles and for the existence of thermal rearrangements to produce quinoline derivatives. A similar analysis of the semi-flexible coil polymer, poly (ether ether ketone ether ketone, PEEKEK) revealed the importance of directed chain-scission processes to form oligomers, carbon monoxide expulsion with radical recombination to produce biphenyl linkages, and aromatic fusions to produce fluorenone-type derivatives. Examination of a “hairy rod” comb-type graft copolymer of PBT and PEEKEK revealed some instability introduced by the grafting process and determined that the graft site thermally isomerized through oxygen migration to yield xanthone-based heterocyclic intermediates of degradation.