Hollow particles synthesized by water-soluble and oil-soluble initiators and the mechanism of incorporating an oil-soluble initiator

Abstract

Monodisperse polystyrene particles were first synthesized by soap-free emulsion polymerization to enhance the monodispersity of hollow particles. Thereafter, the polystyrene particles were immersed in an aqueous solution of 2,2′-azobis(2-methylbutyronitrile) (V-59) to allow the particles to absorb V-59 while maintaining their monodispersity. Thermogravimetric measurements using p-styrenesulfonic acid sodium salt revealed that this absorption occurred not through electrostatic interactions but through hydrophobic ones. Subsequently, the TEOS sol-gel reaction was performed on the polystyrene particle surface to create a silica shell with the help of N-vinyl acetoamide. Finally, the synthesized particles were heated to induce the decomposition reaction of V-59 (which emits nitrogen gas) in the particles, thereby creating a hollow structure as the gas stayed in the particle. These procedures enabled the synthesis of monodisperse hollow particles.