SYNTHESIS AND CHARACTERIZATION OF THERMOTROPIC AROMATIC POLYESTERS DERIVED FROM 3-PHENYL-4,4'-BIPHENYLDICARBOXYLIC ACID

A series of wholly aromatic polyesters were synthesized via bulk, melt polycondensation of 3-phenyl-4,4'-biphenyldicarboxylic acid (PBDA) an d diacetates of aromatic diols such as hydroquinone (HQ), methylhydroq uinone (MHQ), phenylhydroquinone (PHQ), 2-(alpha-phenylisopropyl)hydro quinone (PIHQ), 2,6-naphthalenediol (2,6-ND), 1,4-naphthalenediol (1,4 -ND), and 4,4'-biphenol (BP). The polyesters were characterized for th eir crystallinity, thermal transition properties, and liquid crystalli nity using wide-angle x-ray diffractometry (WAXD) and differential sca nning 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 sho wed optical textures characteristic of the nematic phase when heated a bove their glass transition (T-g) or melting temperatures (T-m). The T -g values ranged from about 125 degrees to 170 degrees C depending on the structure of aromatic diol moieties.