Thermally initiated emulsion polymerization of styrene

The thermal polymerization of styrene in emulsion was studied by determination of the number of particles, the rate of polymerization, and the average molecular weight of the polymer formed as a function of the emulsifier concentration. For the number of particles the relation N ∼ [E]1,4 was found, whereas the rate of polymerization showed a dependence of vbr ∼ [E]0,7, only up to an emulsifier content of 0,2 mol. dm−3, but remained constant at higher concentrations. A transfer of low molecular weight radical species from the organic to the aqueous phase is discussed as a prerequisite of polymerization in the latex particles. The deviations from the Smith‐Ewart theory are explained by the low rate of radical formation, which does not provide a constant radical concentration per particle.