The role of polymerizable surfactants in emulsion polymerization.

摘要

The role of the reactive surfactant sodium dodecyl allyl sulfosuccinate (TREM LF-40) in emulsion polymerization was investigated. Interfacial tension measurements as well as solution homopolymerization studies were conducted to determine its properties.; The polymerization of TREM LF-40 was found to be enhanced in a copolymerization system. In particular, the copolymerization of TREM LF-40 and vinyl acetate was preferred as compared to the copolymerization of TREM LF-40 with styrene, butyl acrylate, or methyl acrylate. The emulsion polymerization of vinyl acetate with TREM LF-40 was studied through a comparison of results obtained using the hydrogenated derivative of the polymerizable surfactant. Opposite behavior was found for the two surfactants; the TREM LF-40 showed a decrease in the polymerization rate with increasing concentration, unusual in emulsion polymerization, while for its hydrogenated derivative the rate increased with increasing surfactant, as expected in emulsion polymerization. Particle size analysis revealed a decreasing particle size with increasing surfactant concentration for both series of reactions. These contrasting results suggested that TREM LF-40 does not act only as a surfactant.; Polymerizations in the aqueous phase and reactions at the particle/water interface were found to influence the polymerization mechanism as well as the loci of the polymerizable surfactant in the resulting latex. Competitive growth experiments using TREM LF-40 and its nonpolymerizable derivative were conducted to separate the effects of aqueous phase and particle surface. Particle size analysis of the seeded and unseeded polymerizations coupled with kinetic results suggested that the reactions at the particle/water interface are the controlling factors compared to polymerization in the aqueous phase. Through a mathematical model developed for the process, the chain transfer to TREM LF-40 at the particle surface was found to be a predominant factor for explaining the kinetic results. The copolymerization of vinyl acetate with TREM LF-40 at the particle surface was also shown to slow the overall polymerization rate. By considering copolymerization in the aqueous phase, at the particle surface, and chain transfer to TREM LF-40 at the particle surface, the model was found to provide a good prediction of the experimental results.