Preparation of monodisperse polystyrene nanoparticles with tunable sizes based on soap-free emulsion polymerization technology

Herein, a one-step procedure for the preparation of monodispersed nanoparticles was achieved, with tunable size in range of around 30~300 nm based on soap-free emulsion polymerization using sodium p-styrene sulfonate as ionic comonomer. The polymerization reaction kinetics (i.e., monomer conversion, particle number, and particle size distribution) were investigated in detail. The experimental results indicated that the particle number increased in low ionic comonomer NaSS concentrations (< 10 wt%). The particle number reached maximum value at 10 wt% NaSS concentration, and minimum particle size nanoparticles (22.3 nm) were obtained. The particle size increased when NaSS concentration exceeded 10 wt%. The particle size distribution of latex gradually narrowed as the polymerization reaction was carried out due to the eversible particle coagulation process and competitive growth kinetics of a particle growth period. This method is conventional and practical for the production of nanoparticles.