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Biphenylene End-Capped Polyaromatics,
COLORADO STATE UNIV FORT COLLINS DEPT OF CHEMISTRY
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Biphenylene end-capped polyquinoline pre-polymers DP3,11 and 22 were melt processed in the presence of a nickel catalyst at 325-340 C under 500 psi to give high quality transparent films. Very short cure times about 5 min were realized, and the resulting films were insoluble, had increased Tgs, and showed improved mechanical properties both above and below the Tg as compared with the uncured resins. The main curing reaction is a chain extension by the conversion of the biphenylene ends to tetrabenzocyclooctatetraene, while a smaller amount of crossslinking takes place. Biphenylene end-capped polyimide, polyketo-ether-sulfone and polyphenylquinoxaline pre-polymers also were synthesized. The polyimide pre-polymer DP3 was melt processed at 325 C and 500 psi Ni catalyst for 15 min to give films that showed good mechanical properties. Friedel Crafts polymerization to yield the biphenyylene end-capped polyketo-ether-sulfone could not be adequately controlled to give reproducible oligomers. Polyphenylquinoxaline pre-polymers were similarly melt processed to give insoluble films with good mechanical properties. Graphite reinforced composites were prepared from biphenylene end-capped polyquinoline and polyimide pre-polymers. The composites showed excellent initial properties and low weight loss after oxidative aging at 316 C. However, the mechanical properties were severely diminished after aging for 50-100 h at 316 C in air.
APPROVED FOR PUBLIC RELEASE