Acrylonitrile copolymerization with a NaClO3/Na2SO3 catalyst. Part I. Effect of 2‐methyl‐5‐vinylpyridine

Batch copolymers, made by polymerizing acrylonitrile, vinyl acetate, and 2‐methyl‐5‐vinylpyridine (MVP) with a chlorate‐sulfite redox catalyst, are fractionated with respect to MVP content when they are fractionated with respect to molecular weight or polymer grain size. Polymer fractions of lowest molecular weight or smallest grain size contain the most MVP. A mechanism is proposed to explain these facts. To test the proposed mechanism, both ultraviolet and electron microscopes are used to study polymer formed during the early stages of batch polymerization. The effects of adding MVP, and of total monomer concentration, on the particles formed are determined. Interpretations of the microscopical observations are compared with the chemical interpretation. When MVP is present, the initial particles formed are more soluble, form colloidal particles less readily, and stabilize the colloidal particles, if formed, due to the charges on the polymer Initial particles with highest MVP content form polymer of lowest molecular weight and aggregate into the smallest polymer grains.