2H nmr analysis of the phenylene motion in different poly(ethylene terephthalate) samples

The detailed characterization of the phenylene motions in phenylene-deuterated poly(ethylene terephthalate) (PET) samples has been performed at different temperatures by solid-state H-2 n.m.r. spectroscopy. Samples used are slowly cooled PET, quenched PET, and quenched PET containing 10 wt% bisphenol-A. H-2 spin-lattice relaxation analyses reveal that there exist three components with different T-1 values at each temperature in each sample, which can be assigned to the crystalline, less mobile noncrystalline, and mobile noncrystalline components in the order of decreasing T-1 value. Using these differences in T-1, H-2 n.m.r. spectra of the respective components are separately recorded, and they are compared to the simulated spectra obtained by the two-site 180 degrees flip model for the motion of the phenylene group. As a result, it is found that the H-2 n.m.r. spectra are successfully reproduced for the respective components by introducing the individual characteristic log-Gaussian distributions in the flip rates. Moreover, the mass fractions of the respective components are determined for each PET sample as a function of temperature. On the basis of these results, the features of the phenylene motions are discussed, particularly in the noncrystalline regions. (C) 1998 Elsevier Science Ltd. All rights reserved.