The molecular weight as a function of temperature in heterogeneous radical‐initiated polymerization

The influence of the polymerization temperature on the stereoregularity and cristallinity of polyvinyl chloride is examined. The crystallizable stereoregular sequences are syndiotactic, and formed by more than four or five monomer units. The relationship between molecular weight and polymerization temperature is determined for polyvinylbromide prepared by heterogeneous bulk polymerization and for polymethylmethacrylate prepared by heterogeneous polymerization in the presence of a preciptant. The results of this work seem to support the suggestion recently developed, that the unusual dependence of the molecular weight on the polymerization temperature, found for some polymers obtained under heterogeneous conditions, is mainly due to structural variations in the products.