Styrene polymerization in ternary microemulsions: effects of water-soluble and oil-soluble initiators

The polymerization of styrene in ternary microemulsions stabilized by the cationic surfactant tetradecyltrimethylammonium bromide was studied as a function of concentrations of water-soluble (potassium persulfate, KPS) and oil-soluble (AIBN) initiators. At a particular molar ratio of the initiators, similar maximum rates of polymerization can be achieved from using both types of the initiators. In addition, both initiated systems produced microlatexes with similar hydrodynamic radius, number of polymer particles, molecular weight of polystyrene and number of polymer chain per latex particle. But the dependencies of these latex parameters on concentrations of KPS and AIBN may not be the same. The polymerization mechanism appears to be similar, irrespective of using KPS or AIBN. It is discussed in terms of effective radicals produced for the polymerization. While the different dependencies of some latex parameters on concentrations of the initiators are attributed to the different efficiencies of the initiators in producing effective radicals.