Kinetics of polymerization of styrene-in-water microemulsions

The kinetics of polymerization of styrene-in-water microemulsions was investigated 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] concentrations the following relationship was established: R _p∝ [styrene]^1.2 [AIBN]^0.46. These exponents are similar to those predicted by the theory of emulsion polymerization. The results also showed a rapid conversion in the initial period (interval 1) followed by a slower rate at longer times (interval 2). It was suggested that in interval 1, the main process in nucleation of the microemulsion droplets, whereas in interval 2 propagation is the more dominant factor. The rapid polymerization of microemulsions is consistent with their structure, whereby very small droplets with flexible interfaces are produced. Received: 2 March 1999 Accepted in revised form: 10 May 1999