Synthesis of nanoscaled poly(styrene-co-n-butyl acrylate)/silica particles with dumbbell- and snowman-like morphologies by emulsion polymerization

Poly(styrene-co-n-butyl acrylate) (P(Sty-co-BuA)) nanoparticles having diameters in the range of 25–60 nm have been successfully synthesized via emulsion polymerization. Sodium styrene sulfonate (SSNa) was used as an ionic comonomer, sodium dodecyl sulfate as a surfactant and divinyl benzene (DVB) as a crosslinking agent. The average polymer particle diameter increased with decreasing the SSNa content in the feed, while increasing DVB concentrations increased the size polydispersity. Dumbbell- and snowman-like P(Sty-co-BuA)/silica biphasic nanoparticles with silica and polymer nodules smaller than typically 60 nm in diameter were obtained by introducing appropriate amounts of 3-(methacryloxy)propyl trimethoxysilane-functionalized silica nanoparticles as seeds in the emulsion polymerization reaction. Neither the quantity of the surfactant nor that of the coupling agent had a strong influence on the obtained morphologies. The control of the number of polymer nodules attached to the silica seed through the modulation of the quantity of silica was also limited, likely because of the low available surface area on each seed in the targeted size range. Consequently, silica–polymer biphasic particles with on average one, two or three polymer nodules at the most were obtained depending on the experimental conditions.