MORPHOLOGY AND LOCAL DYNAMICS IN A SERIES OF AROMATIC TERPOLYESTERS

The molecular morphology and the local dynamics of a series of aromati c terpolyesters based on p-hydroxybenzoic acid, hydroquinone, and isop hthalic acid were investigated using X-ray diffraction and high-resolu tion solid-state C-13 NMR. Correlations between the existence of well- defined crystalline forms and the local mobility of the individual pol ymer units were established. In certain cases, polymers containing les s than 30% p-hydroxybenzoic acid exhibit a crystalline reorganization upon annealing, giving rise to a change in the dominant crystalline fo rm. The C-13 chemical shift tensor parameters were determined from the spinning sideband intensities for the polymers containing 27 and 80% p-hydroxybenzoic acid. Depending on the temperature, two types of mole cular motions were observed for the para-substituted phenyl rings. At low temperatures, there first occur ring oscillations around the para axis; then, at higher temperatures, small-amplitude main-chain reorien tations are involved in the glass transition phenomena. In addition to these findings, a postcondensation with an attendant increase in mole cular weight was detected under annealing for these polymers.