Synthesis and Characterization of Thermotropic Liquid Crystalline Polyesters

Abstract

Synthesis and characterization of polyesters of 4,4′-dihydroxy biphenyl with succinic, adipic, suberic and sebacic acids were carried out. Initially the diacids were converted to the corresponding acid chlorides in dimethyl formamide (DMF). 4,4′-dihydroxy biphenyl was prepared from 4-hydroxy biphenyl by bromination and subsequent hydrolysis. The low molecular weight polyesters were prepared by the condensation of diacid chlorides with 4,4′-dihydroxy biphenyl in DMF at appropriate temperature. All the polymers were characterized by 1H NMR, FT-IR, DSC and hot stage polarizing microscope. Thermotropic liquid crystalline behaviour was established by high temperature X-ray (HTXRD) at various temperature intervals. It was found that among the four compounds prepared, three of them showed nematic phase liquid crystallinity with the exception of the ester of succinic acid.