EFFECTS OF SURFACTANT CONCENTRATION ON POLYMERIZATIONS OF METHYL-METHACRYLATE AND STYRENE IN EMULSIONS AND MICROEMULSIONS

Two ternary systems which can be changed continuously from turbid emulsions to transparent microemulsions have been chosen for polymerization study of methyl methacrylate (MMA) and styrene. The effects of surfactant concentration, either tetradecyltrimethylammonium bromide (TTAB) or octadecyltrimethylammonium chloride (OTAC), on the rate of polymerization (R(p)), number of latex particles (N-d) and molecular weights of the polymers (M(w)) have been investigated. The rate of emulsion polymerization of MMA was found to be faster than that of the microemulsion polymerization. But it was reverse for the styrene systems. Weak dependency of R(p) on the surfactant concentration was observed for the emulsion polymerization of MMA (R(p) proportional to [OTAC](0.13)). However, the dependency was stronger for its microemulsion polymerization (R(p) proportional to [OTAC](0.56)). Similarly, the dependency of Nd on the OTAC concentration was also different between emulsion and microemulsion polymerization of MMA. This is in contrast with the styrene polymerization, which showed only a single dependency for both emulsion and microemulsion systems (R(p) proportional to [TTAB](0.52) and N-d proportional to [TTAB](2.2)). Possible mechanisms related to micellar as well as homogeneous nucleations are discussed to account for the similarities and the differences between the polymerization of MMA and styrene.