Abstract
Polymerization of methyl methacrylate initiated by ceric ammonium nitrate in combination with isobutyl alcohol has been investigated in aqueous nitric acid. The effects of conversion, isobutyl alcohol, Ce(IV) and monomer concentrations, as well as temperature on polymer molecular weight have been studied. Molecular weight distributions obtained by size exclusion chromatography showed several shoulders and a high dispersity index which seemed to be related to the fact that the polymer precipitated continuously during the reaction. Average molecular weights increased initially as conversion increased, while an increase in the isobutyl alcohol and Ce(IV) concentrations up to a certain value caused the molecular weight to decrease. The average molecular weights increased with increasing monomer concentration, but decreased with a rise in temperature. These effects are in agreement with a reaction mechanism involving the oxidation of isobutyl alcohol by Ce(IV) via complex formation, decomposition of the complex giving rise to a primary radical, initiation, propagation, and bimolecular termination of the polymeric radicals and oxidative termination of the primary radical by Ce(IV).