The Regulation of Emulsion Polymerization of Styrene with Anionic–Nonionic Emulsifier Mixtures

The emulsion polymerization of styrene was carried out in the presence of mixtures of a nonionic surfactant (poly(oxyethylene) hexadecyl ether; BC-20) and an anionic surfactant (sodium dodecyl sulfate; SDS or lithium perfluorooctanesulfonate; LiFOS). The polymerization rate changed with the hydrophile-lypophile balance (HLB) of the BC-n series. The polymerization rate considerably increased on the addition of SDS or LiFOS. However, the further addition of LiFOS caused a gradual depression of the polymerization rate. The polymerization rate was not dependent on the amount of styrene solubilized in the mixed emulsifier solution. The particle sizes decreased remarkably on adding SDS. The molecular weights of polystyrene in latex synthesized in mixed emulsifier solutions were larger than those in a single emulsifier solution. The molecular-weight distributions of polystyrene formed in mixed emulsifier solutions were wider than those of polystyrene formed in a single emulsifier solution. These results may be attributed to properties such as the composition and the charge density of the mixed micelles, and to the solubilized amount of styrene monomer in the mixed nonionic-anionic emulsifier solutions.