SYNTHESIS AND CHARACTERIZATION OF LIQUID-CRYSTALLINE POLYMERS FROM P-HYDROXYBENZOIC ACID, POLY(ETHYLENE-TEREPHTHALATE), AND 3RD MONOMERS

Eight new p-hydroxybenzoic acid (PHB) and poly(ethylene terephthalate) (PET) copolymers containing vanillic acid (VA), p-aminobenzoic acid, m-hydroxybenzoic acid, hydroquinone/terephthalic acid (TPA), bisphenol A/TPA, 1,5-naphthalenediol/TPA, 2,7-naphthalenediol/TPA, and. 1,4-dih ydroxyanthraquinone/TPA as eight third monomers with a variety of stru ctural features were synthesized by melted-state copolycondensation an d were characterized through a thermal analyzer, proton nuclear magnet ic resonance, wide-angle X-ray diffraction (WAXD), and a scanning elec tron microscope (SEM). The experimental results show that PHB/PET/VA c opolymers exhibit a faster polycondensation rate, lower melting temper ature, and higher thermostability than do the other seven copolymers a nd third monomer-free PHB/PET polymers. The as-spun fibers derived fro m the PHB/PET/VA copolymers with different VA contents show tensile st rengths, Young's moduli, and break elongations of 0.6-1.5 GPa, 28-67 G Pa, and 7-9%, respectively. A highly oriented fibrillar structure in t he PHB/PET/VA copolymer fibers was observed using WAXD and SEM. The mo st effective third monomer of the eight third monomers for an enhancin g polycondensation rate and molecular weight of the PHB!PET polymers a nd for improving their thermal and mechanical properties is found to b e vanillic acid (VA). (C) 1997 John Wiley & Sons, Inc.