Kinetic simulations of RAFT-mediated microemulsion polymerizations of styrene

Microemulsion polymerizations mediated by reversible addition-fragmentation chain transfer (RAFT) has the potential to produce small polymer particles with controlled molecular weight and molecular weight distributions. This work describes the kinetic simulations using the Smith-Ewart equations to examine the effect of RAFT agent concentration, number of initial droplets and partition coefficient on the rate of polymerization, rate of nucleation and average number of radicals per particle. The simulations showed that exit and reentry of the R radicals from the RAFT agent leaving group dominated the kinetics of microemulsions. The high rate of exit allowed all the droplets to be nucleated under 1% conversion for the high reactive RAFT agents. These simulations further suggest that true compartmentalization only starts upon consumption of the RAFT agent. Retardation and inhibition in the rate of polymerization can be explained through exit and reentry of the R radicals, and one does not require the additional mechanisms of either 'slow fragmentation' or 'intermediate radical termination' (IRT).