Abstract: The particle formation mechanism of monodispersed particles in MMA/BA emulsifier free emulsion polymerization was investigated with Coulter LS230 laser particle size analyzer. The nucleation mechanism of the system is homogeneous nucleation by theoretical and experimental analyses. Athree stage mechanism of the particle formation mechanism of emulsifier-free emulsion polymerization is proposed. Stage 1 is a homogeneous nucleation coagulation stage. The particle number density, N, increases rapidly in this stage, but the particle size changes less. Stage 2 is a nucleation=-coagulation-propagation-aggregation stage. When N begins to decrease rapidly, it marks the end of stage 1 and beginning of stage 2. Stage 3 is a propagation-aggregation stage. When the particle nucleation process ends, it marks the beginning of stage 3. Particle size increases remarkably through propagation and aggregation. Ntends to level off gradually. The precedent aggregation of smaller particles during the propagation leads to produce monodispersed particles.

Key words: Emulsifier-free emulsion polymerization, Nucleation mechanism, Monodispersed particles, Three-stage mechanism of particle formation