Properties and microstructure of aromatic liquid crystalline copolyesters

The properties and structures of thermotropical liquid crystalline copolyesters based on p-hydroxybenzoic acid (PHBA), terephthalic acid (TPR) and bisphenol A (BPA) were studied by DSC, WAXD, hot stage polarized microscopy and NMR. It was found that most of the copolyesters were soluble in many common organic solvents. The copolyesters had low T-m/T-f values and a broad range of liquid crystal phase, making the polymers readily melt-processable. The effects of annealing at different temperatures on the copolyester containing 33% PHBA were also discussed. It was noted that annealing at ca. 200 degrees C (below Tc - n) could lead to the increasing of the crystallinity of the copolyester while the microstructure and sequence structure had not changed. Annealing at ca. 280 degrees C (near Tc - n) could bring a change of crystal and sequence structure and simultaneously made the microdomains be ordered more perfectly.