NMR-STUDIES OF THE LOCAL DYNAMICS OF LIQUID-CRYSTALLINE AND SEMICRYSTALLINE AROMATIC POLYESTERS

The local motions of terpolyesters based on varying amounts of hydroqu inone, hydroxybenzoic acid and isophthalic acid units were investigate d using high-resolution solid-state C-13 NMR. At temperatures below th e glass transition temperature, the mesomorphic polymer having equal a mounts of the three units demonstrates partial motional averaging of t he chemical shift tensors of the aromatic carbons which indicates the existence of oscillations for both para- and meta-substituted rings. T he oscillations of the para-substituted phenyl rings appear to be corr elated with the motions of the adjacent carbonyl groups. At high tempe rature there also occurs small-amplitude main-chain reorientations whi ch are likely to be involved in the glass-transition phenomenon. These motions were also observed in the amorphous phase of other compositio ns of the terpolyester leading to conventional semicrystalline polymer s.