Smirnova, IrinaIrinaSmirnovaArlt, WolfgangWolfgangArlt2022-05-242022-05-242004-05-09Supercritical Fluids as Solvents and Reaction Media: 381-427 (2004-06-11)http://hdl.handle.net/11420/12699This chapter examines the synthesis of silica aerogels and their application as a drug delivery system. The common two-step procedure was modified by the addition of supercritical carbon dioxide (CO2) during the second step. CO2 is commonly used in aerogel production for sol­vent extraction, but its influence on the gelation process itself has not yet been reported. It has been found that the addition of supercritical CO2 during the sol-gel process enhances gel formation. The enhancement factor depends on the aerogel target density and varies from 5 to 100. The CO2 concentration in the liquid phase generally reaches 30 wt% at the gel point. It was evident that the amount of CO2 required-realizing such a rapid gela­tion process-strongly depends on the experimental conditions. The reaction en­hancement takes place only if CO2 is combined with both the catalysts used in the common two-step process; and if one or both catalysts are not used, CO2 addition leads to the rapid precipitation of colloidal particles.enChemieBook Part10.1016/B978-044451574-2/50016-XOther