MORPHOLOGY AND MOLECULAR-MOTION OF POLY(ETHYLENE-TEREPHTHALATE) IN POLYMER OLIGOMER GEL/

The structural heterogeneity and molecular motion in a thermoreversibl e gel consisting of poly(ethylene terephthalate) (PET) and a Liquid et hylene glycol oligomer (PEG) was investigated by solid-state NMR and F T-Raman spectroscopies. PET was dissolved in PEG at elevated temperatu res to form a concentrated solution (30 wt %), and the solution formed a gel rapidly on cooling. For the purpose of comparison, a PET/phenol binary system and PET crystallized by annealing methods were also inv estigated. The longest solid-state NMR relaxation times of C-13 (T-13C (1)) in PET of PET/PEG gel among the samples indicated the slowest mol ecular motion and the highest rigidity PET chains. The structural hete rogeneity of the PET/PEG gel investigated by T-H(1) measurement and co nfirmed by FT-Raman spectroscopy indicated phase transition during gel ation. The crystallinity of PET recovered from polymer/oligomer gels i s near 70% as measured by wide-angle X-ray diffraction, which is about 20% higher than that for PET samples crystallized by solution crystal lization and high-temperature annealing techniques.