Abstract:

Narrowly distributed and size controllable cationic polystyrene(PS) nanoemulsions were prepared through modified microemulsion polymerization with a cationic gemini surfactant as emulsifier without using any cosurfactants. The main feature of the modified microemulsion polymerization is that most of the styrene in the form of preemulsion is postadded gradually into the initiated microemulsion, and the cationic gemini surfactant with high emulsifying property is employed to decrease particle size. The results show that a small amount of trimethylallylammonium chloride used as comonomer can reduce Z-average particle size and size distribution. Emulsifier content, initiator content and reaction temperature can affect particle size and size distribution of obtained colloid particles. The best experimental conditions for preparing the cationic polystyrene nanoparticles with small particle size as well as narrow size distribution are emulsifier content(the mass ratio versus styrene(St) at 5%~10%, initiator content at 1.0%~1.5%, reaction temperature at 70~75 ℃. The linear relationship between the Z-average particle size and St feeding amount demonstrates that Z-average particle size can be controlled by varying the St feeding amount. The result of effects of the polymerization process on the particle size and size distribution of nanoparticles shows that the modified microemulsion polymerization process(semi-continuous and preemulsification) possesses great superiority in preparing narrowly distributed polymer nanoparticles.

Key words: Microemulsion polymerization, Cationic, Nanoparticles, Size controllable, Particle size distribution