FURTHER CHARACTERIZATION OF THE STRUCTURE AND THE THERMAL TRANSITIONS OF POLY(PARA-OXYBENZOATE-CO-PARA-PHENYLENE ISOPHTHALATE) POLYMERS

A series of poly(p‐oxybenzoate‐co‐p‐phenylene isophthalate)s were prepared by melt polycondensation of p‐acotoxybenzoic acid, p‐phenylene diacetate, and isophthalic acid followed by solid‐state polymerization. The solid‐state polymerization not only increased the molecular weight, but also annealed the copolyesters. The thermal stability, liquid crystallinity, thermal properties, and solid‐state crystallinity of these copolyesters were investigated by TGA, polarized microscope, DSC, and wide‐angle X‐ray diffraction, respectively. It was found that copolyesters with HBA content of 50, 60, and 70 mol % showed explicit melt birefringence at 370°C and thus exhibited liquid crystalline state. The effect of annealing during solid‐state polymerization on the thermal properties was discussed. The effect of copolymerization on their crystallinity was interpreted with X‐ray diffraction qualitatively. Copyright © 1990 John Wiley & Sons, Inc.