Preparation and Characterization of Thermotropic Liquid Crystal Polyesters

ORIFICI, A. F.; VALLES, E. M.; GARAY, R O.; LENZ, R. W.

POLYMER

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 1996 vol. 37 p. 4357 - 4364

0032-3861

Wholly aromatic, main-chain copolyesters derived from terephthalic acid and phenylhydroquinone modified with m-hydroxybenzoic acid were prepared and characterized by elemental analyses, 13C nuclear magnetic resonance, thermogravimetric analysis, optical observations, differential scanning calorimetry and wide-angle X-ray diffraction. The phases behaviours depended on copolymer composition. Poly-(p-phenylphenylene terephthalate-co-m-hydroxybenzoate)s with molar percentages of the p-phenylphenylene terephthalate units in excess 70 mol% displayed thermotropic mesophases at relatively low temperatures and exhibited good thermal stability up to about 400°C. Increasing content of m-hydroxybenzoic acid units, which increased the amount of structural irregularity, decreased the isotropization temperature and the temperature at which the melt started to flow, and also caused a loss of both crystallinity and of liquid crystallinity.