Influence of Degree of Polymerization on Phase Separation and Rheology of A Thermotropic Liquid Crystal Polymer

Abstract

Dynamic rheometry and both high-temperature and solution NMR spectroscopy measurements were carried out on a series of thermotropic liquid crystal copolymers of 60 mole percent hydroxybenzoic acid and 40 mole percent poly (ethylene terephthalate); the members of the series differed only in the extent of solid phase polymerization. The viscosity decreased with increasing degree of polymerization, reaching a broad minimum after about five hours of solid phase polymerization. Solution NMR spectra showed only a slight deviation from chain randomness. Wide-line NMR spectra at 210° and 265° C showed that all members of the series contained both isotropic and nematic phases, with the nematic fraction increasing with polymerization time.