Abstract: Miniemulsion copolymerization of styrene/butyl acrylate was investigated by redox initiator(NH₄)₂S₂O₈/NaHSO₃ at lower temperature and contrasted it to convention emulsion polymerization. Monomer droplet of the former is several ten times of microns(5~20 μm), and that the latter is in the range of submicron(100~400 nm). The change of particle size and distribution in polymerization process were determined in miniemulsion polymerization process. It is fuond that the particle size decreased with increasing of surfactant, cosurfactant, initiator concentration, but the distribution became wider. In addition, it is bigger than convention emulsion polymerization. The changes rule of particle number and the surfactant-covering ratio were calculated. The effects of initiator and emulsifier on polymerization process and the difference of nucleation mechanism between miniemulsion and conventional emulsion were discussed.

Key words: Miniemulsion copolymerization, Particle size distribution, Nucleation mechanism, Redox initiator