On the fine emulsion polymerization of styrene with non-ionic emulsifier

The fine emulsion polymerizations of styrene initiated by a redox system am monium peroxodisulfate/sodium thiosulfite stabilized by a non-ionic emulsif ier were kinetically investigated. The dependence of the rate of polymeriza tion on conversion or the emulsifier concentration was described by a curve with maximum at medium conversion. The maximum rate of polymerization is p roportional to the - 0.45(th) and 1.5(th) power of initiator and emulsifier concentration, the number of particles to the 0.32(nd) and 1.3(rd) power o f initiator and emulsifier concentration and the molecular weight to the 0. 62(th) and -0.97(th) power of initiator and emulsifier concentration, respe ctively. The results show a strong decrease in turbidity at around 20% conv ersion when emulsion turns into translucent latex. Deviation from the micel lar nucleation model was attributed to the solubility of emulsifier in mono mer, high level of nonmicellar aggregates, thick interfacial layer and tran sfer emulsion to microemulsion. The strong decrease of molecular weight wit h increasing emulsifier concentration is attributed to chain transfer event s promoted by the high level of emulsifier at the reaction loci.