Control of Flexibility, Pore Structure and Hydrophobicity of Tetraethylorthosilicate/Methyltriethoxysilane Aerogels by Hybridization.

The flexibility, pore structures and hydrophobicity could be controlled by changing TEOS/MTEOS ratio. A methyl functional group of MTEOS causes the difficulty of hydrolysis and condensation reactions, so that strong basic catalyst needs to be added for the gelation of MTEOS. Therefore, increasing of MTEOS ratio forms larger pore sizes and large primary particles with about one micrometer. MTEOS-based aerogels show the lowest specific area due to macropores with more than one thousand nanometers, although they are very flexible to elongate two times as long as their original sample length. For TEOS/MTEOS hybrid aerogels with 0.4-0.6 of TEOS ratio, they have the large specific surface area and pore volume, a little flexibility and hydrophobicity due to the remaining alkyl functional groups. This research presents the possibility of controlling flexibility, pore structures, hydrophobicity through hybridization of alkoxide and silane. It suggests a way of overcoming weaknesses of silica aerogels like brittleness and hydrophilicity.