Emulsion polymerization of styrene using conventional, polymerizable, and polymeric surfactants. A comparative study

The emulsion polymerization of styrene is investigated, employing analogous conventional, polymerizable, and polymeric cationic surfactants (''polysoaps''). The polymerization and the properties of the latexes depend sensitively on the emulsifier and on the charge of the initiator. There is no visible correlation between the properties of the final latexes and the properties of the emulsifiers such as surface activity, solubilization capacity, or the ability to stabilize the initial monomer emulsion. When a cationic initiator is employed, all emulsifiers lead to stable monodisperse latexes, except for polysoaps with low hydrophobe content. The polymerizable, as well as the polymeric emulsifiers, yield latex solutions with very high surface tensions, different from the use of the standard surfactant. In contrast, the use of an anionic initiator can pose difficulties. The polymerizable emulsifier is efficiently fixed to the latex by copolymerization, being mostly consumed in the early stage of the reaction. Also, small amounts of the polysoaps are grafted onto the latexes during the reaction.