Synthesis and Characterization of Thermotropic Aromatic Polyesters Derived from 3-Phenyl-4.4′-biphenyldicarboxylic Acid

Abstract

A series of wholly aromatic polyesters were synthesized via bulk, melt polycondensation of 3-phenyl-4.4′-biphenyldicarboxylic acid (PBDA) and diacetates of aromatic diols such as hydroquinone (HQ), methylhydroquinone (MHQ), phenylhydroquinone (PHQ), 2-(α-phenylisopropyl) hydroquinone (PIHQ), 2,6-naphthalenediol (2,6-ND), 1,4-naphthalenediol (1,4-ND), and 4,4′-biphenol (BP). The polyesters were characterized for their crystallinity, thermal transition properties, and liquid crystallinity using wide-angle x-ray diffractometry (WAXD) and differential scanning calorimetry (DSC), and by observation of their optical textures under a polarizing microscope. It was found that all of the polyesters, with the only exception of the BP polyester, are amorphous. They showed optical textures characteristic of the nematic phase when heated above their glass transition (T g) or melting temperatures (T m). The T g values ranged from about 125° to 170°C depending on the structure of aromatic diol moieties.