Emulsifier-Free, Organotellurium-Mediated Living Radical Emulsion Polymerization of Styrene: Polymerization Loci

The effect of polymerization temperature in emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) on the control/livingness and particle size distribution was investigated at 50, 60, and 70 °C. The size distribution of obtained particles was significantly affected by the polymerization temperature, that is, nanometer-sized particles at 50 °C, submicrometer-sized ones at 70 °C and both particles at 60 °C were obtained. At 60 °C the molecular weight distribution of the nanometer-sized particles was narrower than that of the submicrometer-sized ones. M w/M n at 70 °C was much high (4.6), on the other hand, it was 1.5 at 50 °C and a middle value (2.0) at 60 °C. When the polymerization temperature was changed from 50 to 60 °C during the emulsion TERP, the particle size distribution and control of molecular weight distribution were, respectively, similar to those at 50 °C. From these results, it is concluded that the particle formation by self-assembly nucleation in the early stage of the emulsion TERP is important for the formation of the monomodal nanometer-sized PS particles with good control/livingness.