Preparation of silica microcapsules by sol-gel method in W/O emulsion

Spherical silica microcapsules whose average diameter was 3.6 mu m were synthesized by the sol-gel method in W/O emulsions containing an anionic surfactant at a high water to surfactant molar ratio. Special agitational conditions are needed to prepare spherical silica microcapsules. The properties of the resulting silica microcapsules were determined by Fourier-transform infrared spectroscopy and scanning electron microscopy. As the spherical silica particles have a hollow core structure, hydrolysis and condensation of TEOS occur at the micellar periphery, and the diameter of the water droplets in the W/O emulsion at a high water to surfactant molar ratio (Wo) are micron sized.