Efficient preparation and formation mechanism of polymer/SiO2 nanocomposite particles in miniemulsions

Poly(styrene- co -methyl methacrylate) (poly(St- co -MMA))/SiO 2 nanocomposite particles (NCPs) were prepared through miniemulsion polymerization by using polyoxyethylene (20) sorbitan monolaurate (commercial name: Tween-20) as the sole surfactant. The number fraction of poly(St- co -MMA)/SiO 2 NCPs in the as-synthesized emulsion could exceed 90% in some well-designed systems, indicative of high efficiency of poly(St- co -MMA)/SiO 2 NCP formation. Each poly(St- co -MMA)/SiO 2 NCP contained many SiO 2 NPs, thus exhibiting a high composite efficiency between the poly(St- co -MMA) and SiO 2 NPs. The mechanistic investigation indicated that the enhanced efficiency of the poly(St- co -MMA)/SiO 2 NCP formation is due to the improved homogeneity in the distribution of SiO 2 among the monomer droplets and the effectively suppressed nucleation of plain monomer droplets through controlled coalescence of the monomer droplets with the latex particles.