SiO₂-Coating of Polystyrene Particles by Sol-Gel Process

Abstract

Polystyrene particles with an average diameter of 15gm were uniformly coated with a SiO₂ thin film. Prior to the coating, the surface of polystyrene was activated by oxygen-microwaveplasma treatment. After the particles were dispersed into an ethanol solution of tetraethoxysilane with a small amount of NH₃ water as a base catalyst, a 3 hoars' stirring at room temperatu re accomplished the sol-gel SiO₂ coating. XPS spectra of the particles treated with oxygen-microwave plasma indicated the introduction of polar groups such as hydroxyl and carboxyl ones on the surface. In diffuse reflectance FT-IR spectra of the particle finally obtained, two absorption peaks assigned to Si-O-Si and Si-OH stretching vibrations were observed at 1100 and 950cm^-1, respectively. EPMA and TEM analyses of the cross section of the particle clearly demonstrated that the polystyrene particles with oxygen-plasma pretreatment were homogeneously covered with a SiO₂ film having a thickness of ca. 120 nm, while the particles without pretreatment were heterogeneously covered with SiO₂ particles.