Application of Silica Aerogel Carrier via Supercritical Drying for Fragrance Controlled-release

Silica aerogel with different hydrophilicities were prepared from tetramethoxysilane, Methymethoxysilane, tetramethoxysilane-propyltrimethoxysilane, or tetramethoxysilane-phenyltrimethoxysilane mixtures via supercritical drying process (labelled as TMOS-AG Me-TMOS-AG, Pr-TMOS-AG, or Ph-TMOS-AG, respectively). Three fragrances, including geraniol, ethyl vanillin, and menthol, were loaded to TMOS-AG. The thermal analysis confirmed all loading fragrances are stable until over 200 °C. And among all fragrances, geraniol presented the maximum loading contents ( L m ). Concentration dependences indicated the geraniol was mono layer absorbed. Py-GC/MS of geraniol in TMOS-AG under both N 2 and mimic air atmosphere (90% N 2 and 10% O 2 ) confirmed that loaded geraniol could be thermally controlled-released beginning at 200 °C. As N 2 absorption confirmed, even absorption/desorption equilibrium constant ( k ) was determined mainly by hydrophilicity of silica aerogels, and the maximum loading contents ( L m ) were influenced more by the pore size. Due to mono layered absorption, bigger pores usually give less specific areas and less absorbing sites for geraniol, and then present lower L m .