NEW POLYMER SYNTHESES .42. THERMOTROPIC POLYESTERS OF HYDROQUINONE AND VARIOUS ARYLOXYTEREPHTHALIC ACIDS

Aryloxyterephthalic acids were prepared from dimethyl nitroterephthalate and phenol, 4‐fluoro, 4‐chloro‐, 4‐bromo‐, 4‐phenyl‐, 4‐cyclohexyl‐, 4‐phenoxy‐ and 4‐cumyl phenol. Polycondensations with hydroquinone or its derivatives gave the best results, when the aryloxyterephthaloyl chlorides were condensed with hydroquinone in pyridine or with silylated hydroquinone in the molten state. The resulting polyesters were characterized by elemental analyses, inherent viscosities, DSC measurements, microscopy under polarized light, WAXS measurements, and thermogravimetric analyses. All polyesters derived from hydroquinone are semicrystalline with melting points (Tm) in the range of 300–370°C and glass transitions (Tg) in the range of 80–110°C. Most of them form a nematic phase above their Tm; only the homopolyesters of napthyloxy and (4‐cyclohexyl phenoxy) terephthalic acid are isotropic above Tm. Yet the amorphous copolyester of both terephthalic acids and hydroquinone is nematic above Tg, like all copolyesters prepared from two differently substituted terephthalic acids. Copyright © 1990 John Wiley & Sons, Inc.