MOLECULAR-MOTION AND DISTINCTIVE FEATURES OF THE STRENGTH OF THERMOTROPIC LIQUID-CRYSTAL ORIENTED POLYMERS

Nuclear magnetic resonance (NMR) is used to study molecular motion in two fully aromatic oriented liquid-crystal (LC) polymers (the copolyme r with the brand name Vectra and poly-para-phenylphenyleneterephthalat e) at high temperatures up to 610 K. Above the temperature of the ther motropic transition, a fine structure is observed in the NMR spectra a nalogous to structures seen previously only in studies of low-molecula r-weight LC materials. Analysis of the results indicates that macromol ecules in the LC state participate in cooperative types of motion. The relation between structural rearrangements and hardening during therm al processing is discussed, along with the role of distinctive feature s in the molecular motion in the mesophase. (C) 1998 American Institut e of Physics.