Living free-radical emulsion polymerization of methyl methacrylate (MMA) using a surface active iniferter (suriniferter): Polymerization parameters and molecular structure of the latex

A novel surfactant active RAFT agent as a suriniferter, composed of dithiobenzoyl main structure and benzoic hydrophobic/carboxylate hydrophilic moiety, was synthesized and applied to living radical emulsion polymerization of methyl methacrylate (MMA) initiated by UV irradiation in the absence of added surfactant and additional initiator at various temperatures. Stable spherical PMMA beads were successfully obtained using the suriniferter, maintaining the living radical polymerization characteristics, which shows a linear increase in molecular weight with respect to the conversion. The PDI varies from 1.21 to 1.43 and the final particle sizes vary from 407 to 304 nm with increase in polymerization temperature from 60 to 80degreesC. It is found that the polymerization is greatly retarded due to an increasing agitation speed. In addition, the increased agitation speed results in reduction of molecular weight and particle size without alternating the stability of the PNMA colloids. The triad tacticity of PMMA prepared with various concentration of suriniferter at several temperatures shows higher syndiotacticity in the range of 55.5 similar to 57.9% compared to commercial PMMA, inducing significantly high glass transition temperature. Thus, it is believed that the suriniferter used in living free radical emulsion polymerization modifies the stereoregularity of the PMMA.