Miniemulsion polymerization of styrene with liquid polybutadiene as the sole co-stabilizer

A low-molecular-weight liquid polybutadiene (LPB) is employed as the sole co-stabilizer in miniemulsion polymerization of styrene in present work. Results indicate that the LPB can be used as an effective co-stabilizer to retard the diffusional degradation of monomer droplets in miniemulsion system and get stable miniemulsions. When the miniemulsions were initiated, particle formation occurred predominantly by monomer droplet nucleation. Moreover, the effects of various reaction parameters on the polymerization kinetics and the nucleation mechanisms were also investigated. These parameters include the level of LPB ([LPB]) and the concentrations of SDS ([SDS]) and potassium persulfate ([KPS]). It is shown that the polymerization rate indicates little dependence on [LPB], while increases with increasing [SDS] and [KPS]. Competition between droplet nucleation and homogeneous nucleation occur in the course of polymerization, but droplet nucleation becomes more important by increasing [LPB] or decreasing [SDS]. Furthermore, the result that the particle size is rather insensitive to changes in [KPS] provides the most compelling evidence for the dominant droplet nucleation.