Molecular aggregation in poly(vinyl chloride)

Molecular weight distributions and molecular aggregation for poly(vinyl chloride) (PVC) polymerized in bulk at −10, −30, and −50°C have been measured using gel permeation chromatography. The aggregate content in PVC polymerized at −50°C was found to be 87 wt‐%. These spherical aggregates of mean diameter of 5000 A are formed preferentially from PVC chains having high molecular weights and long syndiotactic sequence lengths. A temperature of 200°C was used to disintegrate these aggregates into single PVC molecules. In disagreement with measurements of Mn and Mw published in the literature, our measured values do not reach a minimum but rather increase continuously with decreasing temperature of polymerization. This disagreement is most probably due to the phenomenon of molecular aggregation in PVC.