STRUCTURE AND PROPERTIES OF LIQUID-CRYSTALLINE NAPHTHALENEDIOL COPOLYESTERS

Thermotropic liquid crystalline copolyesters with 1.4-, 1.5-, and 2.7-naphthalenediol (NDO) units were prepared by molten-state copolycondensation. It was found that the chain structure of the copolyesters is almost the same as the structure of recurring moieties of five units. The copolyesters have a glass transition temperature above 381 K, decomposition temperature above 703 K, and melting temperature between 513 and 559 K and their melts exhibit nematic texture and stir opalescence. The copolyester melts show a usual rheological behavior depending on the NDO unit content, but much lower extrudate swell. Light-scattering patterns of the copolyester films with low crystallinity are clearly asymmetric and therefore indicate the existence of preferred orientation of the copolyester chains. Scanning electron microscopy observation suggests that the as-spun fibers of 2.7-NDO-containing copolyesters were highly oriented and fibrillated. (C) 1994,John Wiley & Sons, Inc.