NUCLEAR-MAGNETIC-RESONANCE STUDIES OF HIGHLY ORIENTED LIQUID-CRYSTALLINE COPOLYESTERS

Highly oriented copolymers prepared from 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid and having monomer ratios of 73:27 and 30:70 have been studied by modelling the second moment anisotropies of their nuclear magnetic resonance proton lineshapes. At -100-degrees-C the results are consistent with chains of immobile aromatic rings placed on a pseudo-hexagonal lattice. As temperature is increased the changes in the second moment anisotropies are accounted for by allowing first the phenyl and then the naphthalene rings to acquire rapid rotational motion. It is also necessary to introduce an accompanying increase in the distribution of chain axes about the sample draw direction. This may be due to increasing chain motion.