A new kinetic interpretation of the styrene microemulsion polymerization

The polymerization of styrene initiated by potassium peroxodisulfate was conducted at 50°C in oil‐in‐water microemulsions using sodium lauryl sulfate and 1‐pentanol as emulsifier and cosurfactant, respectively. Based on the experimental findings that both particle size and molecular weight of the polymers are almost independent of styrene conversion and the initial initiator concentration, a kinetic scheme of the microemulsion polymerization of styrene is proposed, which assumes that (1) particle nucleation occurs in monomer‐swollen micelles and almost all the radicals in the water phase enter the monomer‐swollen micelles and finally initiate polymerization therein, (2) with negligible radical termination in the water phase and (3) with negligible radical entry into the preformed polymer particles, and accordingly, (4) all chain‐stopping events in the active polymer particles are chain transfer reactions to monomer. Based on this kinetic scheme, a simple kinetic model is proposed, which can explain fairly well the progress of styrene microemulsion polymerization in the initial stage.