Fabrication of Hollow Polystyrene Nanospheres in Microemulsion Polymerization Using Triblock Copolymers

Abstract

A ternary microemulsion polymerization was successfully used to prepare nanosized hollow polystyrene (PS) microlatexes with triblock copolymers of poly(oxyethyene)-poly(oxypropylene)-poly(oxyethylene)- [(EO)x(PO)y(EO)x]. Micelle formation using triblock copolymers is a useful nanoreactor in order to make polymer nanoparticles in oil/water (o/w) microemulsions. Poly(methyl methacrylate)/cross-linked polystyrene core/shell nanospheres have been fabricated by o/w microemulsion. PS hollow nanospheres were obtained using the polymer core etching technique. Water-soluble and oil-soluble initiators were used for the polymerization at 70 °C with moderate stirring and via modified buret feeding. After extraction of the surfactant matrix, the polymer particles contract considerably without the change of their spherical shape. The hollow sphere morphology and hollow image of the polymer particles were confirmed by field emission scanning electron microscope and transmission electron microscope. PS hollow spheres were fabricated with diameters in the range of ca. 15-30 nm, and the shell thickness was ca. 2-5 nm. The size of the hollow nanoparticle is dependent on the surfactant concentration and the weight ratio of [surfactant]/[monomer].