Synthesis of silica microspheroids for templates in W/O reverse emulsion

About 10 μm-sized silica microspheroids were synthesized by emulsion-gel method in W/O reverse emulsion medium. For the formation and the stabilization of W/O emulsion, hydroxypropyl cellulose (HPC) and sorbitan monooleate (Span 80) were used. Poly(ethylene oxides)-b-poly(propylene oxides)-b-poly(ethylene oxides) (PEO-PPO-PEO) triblock copolymer EO20PO70EO20 (P123) was used to control the arrangement of water droplets and obtain silica microspheroids. Depending on the type of catalysts used in the water phase containing EO20PO70EO20 (P123) polymer, the morphology of water droplets and silica particles was changed. For hydrochloric acid (HCl) catalyst, water droplets were linearly arranged and mutually linked, while for ammonium hydroxide catalyst, such phenomena were not observed. Also, the porosity and the density of silica surface were greatly changed, according to the kind of catalysts. As a result, sol-gel reaction process under the low pH condition has a strong influence on the synthesis of silica microspheroids. Their external appearance and surface shape were observed by FE-SEM, optical microscopy and BET surface area measurement.