Synthesis and characterization of potentially biodegradable thermotropic polyesters based on p‐hydroxybenzoic acid and glycolic acid

Abstract

AbstractThe synthesis of novel thermotropic liquid crystalline copolyesters derived from aliphatic hydroxy acid (glycolic acid, GA) and aromatic hydroxy acid (p‐hydroxybenzoic acid, PHBA) via a melt‐copolycondensation process in the presence of various catalysts was explored. The following three possible routes were checked: PHBA and GA in different feed ratios with or without a catalyst; PHBA and GA in different feed ratios with or without a catalyst in the presence of acetic anhydride as a condensation agent; and different PHBA derivatives were used to examine the reactivity of aromatic hydroxy acid. The copolycondensability, chemical structure, liquid crystallinity, textures and morphology, phase transition behaviors and thermal stability, and solubility were investigated by FTIR, NMR, DSC, TGA, and polarized‐light microscope. It has been found that only the 60–70 mol % PHBA‐containing copolyesters could exhibit a nematic liquid crystallinity. The as‐prepared polymers were brittle due to relatively lower molecular weights. © 1994 John Wiley & Sons, Inc.