Acrylonitrile polymerization in aqueous suspension

Polymerization of acrylonitrile in dilute aqueous solution initiated by the chloratesulfite redox was studied kinetically and with the aid of the electron microscope. Polymerization rate depended on the [ClO ] [H2SO3] product, the monomer content and the sodium lauryl sulfate concentration. The rate was depressed by agitation and by salts; it was accelerated by Fe++ and by Cu++ and was only moderately dependent on temperature. Particles of polymer separated from the start as spheroids less than 200 A. across and grew rather uniformly to 2000 to 3000 A. After a short time no new particles formed unless more initiator was added. Rate of polymerization per particle was reasonably constant. Salts and agitation led to aggregation of particles and polymerization rate was reduced. Sodium lauryl sulfate and Methocel had the opposite effect. The system bears a general resemblance to typical emulsion polymerization, and thus treatments based on homogeneous kinetics appear to be inadequate.