Synthesis and characterization of liquid crystal polyesters with T-shaped two-dimensional mesogenic units (III)

A new series of liquid crystal polyesters with T-shaped two-dimensional mes ogenic units were synthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-r ay diffraction. It was realized that all the polymers have nematic thermotr opic liquid crystalline characteristics. The melting temperature (T-m) and isotropization temperature (T-i) of the polymers change regularly with vary ing lengths of the alkoxy side group;Ind the: length of the alkylene group in the main chain in company with an even-odd effect. Thr mesophase tempera ture range also varies regularly with the polymer structure. It is shown th at the mesophase range has been widened.