Molecular aggregation in poly(vinyl chloride)

PVC synthesized in a bulk polymerization at −25°C was fractionated by preparative GPC. The eluent THF solutions consist largely of dissociated molecules. Following precipitation into methanol, recovered PVC fractions contain aggregated molecules and are partially insoluble in THF. The soluble portions produce distorted chromatograms characteristic of molecular aggregation. The aggregate fraction increases with molecular weight. Heating recovered PVC fractions at 90°C in THF was adequate to dissociate the aggregates. Following recovery, fractions of PVC do not show crystalline x-ray diffraction patterns. The PVC fractions were crystallizable by subsequent annealing at 150°C to approximately 15% crystallinity, largely independent of molecular weight.