Preparation of Dimpled Polystyrene-Silica Colloidal Nanocomposite Particles

Preparation of polymer-silica colloidal nanocomposite particles with concave shape is challenging and seldom reported. This paper presents a novel and facile method to prepare dimpled polymer-silica nanocomposite particles with a thin silica shell through the judicious combination of alcoholic dispersion polymerization and the decane evaporation method. Submicrometer-sized polystyrene-silica (PS-SiO₂) nanocomposite particles were first prepared by dispersion polymerization of styrene in methanol in the presence of a methanolic silica sol, and then dimpled PS-SiO₂ particles were prepared by heating the near-spherical PS-SiO₂ particles dispersed in methanol/water media in the presence of decane and subsequent cooling. The effects of different heat treatment parameters, such as methanol/water ratio, stirring temperature, and stirring rate on the formation of the nanocomposite particles were investigated. Optimization of the heating conditions allowed ∼100% of dimpled particles to be achieved with one dimple on each particle. Moreover, calcination of the dimpled PS-SiO₂ nanocomposite particles led to the formation of hollow dimpled particles with a thin silica shell. This method is expected to enrich the shapes of polymer-silica nanocomposite particles.