Published online by Cambridge University Press: 01 February 2011
Transparent organic-inorganic hybrid aerogels and aerogel-like xerogels have been prepared from methyltrimethoxysilane (MTMS) respectively by supercritical drying (SCD) and ambient pressure drying (APD). The new aerogels and xerogels significantly deform without collapsing on uniaxial compression and almost fully relax when unloaded. This elastic behavior, termed as “gspring-back”, allows APD without noticeable shrinkage and cracking. The flexible network composed of lower cross-linking density (up to three bonds per every silicon atom) compared to silica gels (up to four bonds) and repulsion between hydrophobic methyl groups bonded to every silicon atom largely contributes to the pronounced deformability and relaxing, respectively. Lower surface silanol group density also plays a crucial role for the “gspring-back” behavior.