The emulsion polymerization process has been discussed in a number of publications.1-9 The primary role of surfactants in emulsion polymerization is to lower the interfacial tension, which allows the emulsification of reactive vinyl monomers and the formation of stable colloidal dispersions of nano-size polymer particles. Conventional surfactants aid in the emulsification of monomers inside the micelles, stabilize the polymer particles during nucleation and growth and promote the stability of the resulting latex.
Surfactants have a strong effect in reducing the surface tension between the water and the air, as well as the interfacial tension between the water and otherwise immiscible liquids such as vinyl monomers. The practical fact that commercial emulsion polymerizations can be run smoothly and quite rapidly with many water-insoluble monomers is due to the presence of surfactants. Normally, surfactants are used in concentrations well above their critical micelle concentration (CMC).