Miniemulsion Polymerization of Styrene Initiated by Tween-surfinit

The sterically-stabilized miniemulsion polymerization of styrene initiated by peroxide-containing Tweens (Twper, surfinit) was investigated. The conversion curves for miniemulsion emulsion polymerization are concave downward throughout the polymerization and the observed limiting conversions are much below 100% conversion. The polymerization rate vs conversion curve is described by a curve with two rate intervals and rate maximum located at low conversion. The consumption of peroxide groups in Tween (Twper), including their immobilization and accumulation into micelles, leads to the dead-end polymerization. The maximal polymerization rate increases with increasing the emulsifier and peroxide concentrations. The particle size decreases and the number of particles increases with increasing the concentration of emulsifier, Twper and reducing agent. The increased stability of the polymer dispersions is attributed to the chemically bound moieties of Twper to the particle surface. The values of the ratio of the final number of polymer particles to the initial number of monomer droplets (N p /N d) favor the mixed mode of particle nucleation.