Functional Groups of Organochlorosilanes Influenced Microporous Structure in Organosiloxane Microcapsules Synthesized Using a Water-in-Oil Emulsion Template

Studies on functional groups in organosilyl chlorides have focused on their contribution to the resulting structure and morphology of porous hollow polyorganosiloxane microspheres. The silane coupling agents employed included trifunctional (octylsilyl, methylsilyl, and phenylsilyl trichlorides) and bifunctional (dimethyldisilyl dichloride) silanes. These organosilanes participated in sol-gel reactions (hydrolysis and polycondensation) to produce hollow microspheres at the interfaces of aqueous droplets in a water-in-oil emulsion. Phenylsilyl groups contributed to forming smaller spherical hollow particles via an emulsification effect, while dimethyldisilyl groups deformed the hollow shape. Trifunctional methylsilyl groups allowed the formation of a microporous structure with a large surface area (approximately 400 m(2)/g), where bulky organic groups (octyl and phenyl) buried the micropores to reduce the specific surface area. These bulky groups were removed via oxidative decomposition to transform microporous polymethylsiloxane. Hence, trifunctional methylsilyl groups were key for tailoring microporous hollow spherical organosilica particles via emulsion templated syntheses.