RAFT-Mediated Emulsion Polymerization of Styrene with Low Reactive Xanthate Agents: Microemulsion-like Behavior

Abstract

Xanthates ([1-(O-ethylxanthyl)ethyl]benzene (CTA1) and [1-(O-trifluoroethylxanthyl)ethyl]benzene (CTA2)) have the capacity to control the molecular weight distribution in emulsion polymerizations to produce very small nanoparticles below 20 nm. We form stable translucent polystyrene latexes using surfactant (sodium dodecyl sulfate, SDS) and a small amount of pentanol as cosurfactant. The high CTA concentration results in a greater retardation in rate until consumption of all the RAFT agent. With an increase in CTA1 the particle size decreases from 38 to 8 nm and the particle number concentration Nc increases from 2 × 1018 to 2 × 1020 particles/L. Although an increase in Nc should in principle lead to a faster rate of polymerization, we observe a greater retardation in rate with increasing CTA. The higher Ctr,RAFT of CTA2 results in a greater initial retardation until consumption of all the RAFT agent and particle diameters lower than 5 nm and at high concentrations of CTA2 diameters that are not measurabl...