Kinetics of polymerization of styrene-in-water microemulsions

The kinetics of polymerization of styrene-in-water microemulsions was inves tigated using dilatometry. From plots of percentage conversion versus time, the rate of polymerization, R-p, was determined. From log-log plots of R-p versus styrene and initiator [2,2'-azobis(isobutyronitrile), AIBN] concent rations the following relationship was established: R-p proportional to [st yrene](1.2)[AIBN](0.46). These exponents are similar to those predicted by the theory of emulsion polymerization. The results also showed a rapid conv ersion in the initial period (interval 1) followed by a slower rate at long er times (interval 2). It was suggested that in interval 1, the main proces s in nucleation of the microemulsion droplets, whereas in interval 2 propag ation is the more dominant factor. The rapid polymerization of microemulsio ns is consistent with their structure, whereby very small droplets with fle xible interfaces are produced.