RAFT/MADIX miniemulsion polymerization of vinyl acetate: influence of oil soluble initiators, temperature, and type of chain transfer agent in nanodroplets

Abstract

The influence of hydrophobic initiators, temperature, type of chain transfer agent, and average particle diameter (Dp) of miniemulsions over the control of the RAFT/MADIX polymerization of vinyl acetate (VAc) was analyzed. The kinetic profiles demonstrated that polymerization displayed living controlled characteristics below 60% conversion but also showed a drop in the polymerization rate. The R group in the RAFT agent was critical: better control was observed when the R group was methyl ethoxycarbonyl than when it was cyanoisopropyl. As a part of the results, poly(vinyl acetate) (PVAc) with a number average molecular weight (Mn_GPC) of 105,000 g/mol and 75% conversion was obtained. The dispersity, Ð = 1.8, was close to previous reports, confirming the difficulty in the control of the RAFT polymerization of this less-active monomer. Dynamic light scattering analyses revealed variations in particle diameter and in the particle size distribution, particularly when an induction period was observed.