A NEW KINETIC INTERPRETATION OF THE STYRENE MICROEMULSION POLYMERIZATION

The polymerization of styrene initiated by potassium peroxodisulfate w as conducted at 50 degrees C in oil-in-water microemulsions using sodi um lauryl sulfate and l-pentanol as emulsifier and cosurfactant, respe ctively. Based on the experimental findings that both particle size an d molecular weight of the polymers are almost independent of styrene c onversion and the initial initiator concentration, a kinetic scheme of the microemulsion polymerization of styrene is proposed, which assume s that (1) particle nucleation occurs in monomer-swollen micelles and almost all the radicals in the water phase enter the monomer-swollen m icelles and finally initiate polymerization therein, (2) with negligib le radical termination in the water phase and (3) with negligible radi cal entry into the preformed polymer particles, and accordingly, (4) a ll chain-stopping events in the active polymer particles are chain tra nsfer reactions to monomer. Based on this kinetic scheme, a simple kin etic model is proposed, which can explain fairly well the progress of styrene microemulsion polymerization in the initial stage.