Kinetics of miniemulsion polymerization with nonionic and anionic surfactants

The kinetics of miniemulsion polymerization of vinyl acetate, in which noni onic surfactant, Brij-35 [polyoxyethylene(23) lauryl ether], and hexadecane were used, was investigated. For comparison, experiments were also carried out using an anionic surfactant (sodium lauryl sulfate). The results show that, for all experiments, both distributions for the particle size of the latices and the molecular weight of polymers were unimodal. The effects of surfactant and initiator levels on the particle number and the polymerizati on rate were studied. For the system using Brij-35, the power orders for th e dependence of particle number on surfactant and initiator concentrations were 1.33 and 0.68, respectively. The polymerization rate was proportional to the 0.38 power of surfactant level and the 0.84 power of initiator conce ntration. The hydration layer outside the monomer-swollen particles in the system of nonionic surfactant may exert a retardation effect on the entry o f oligomeric radicals into the particles. The result of GPC analysis indica tes that the surfactant concentration inversely affects the molecular weigh t. (C) 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1691-1699, 2001.