Methyltrimethoxysilane based monolithic silica aerogels via ambient pressure drying

We have developed a novel route to monolithic silica aerogels via ambient pressure drying by the acid-base sol-gel polymerization of methyltrimethoxysilane (MTMS) precursor. An extent of silica polymerization in the alcogels plays a crucial role in obtaining the monolithic aerogels which could be optimized by a proper control over the MeOH/MTMS molar ratio (S) during the sol-gel synthesis. The alcogel undergoes the distinct "spring-back effect" at the critical stage of the drying and thereby preserving the highly porous silica network without collapse. The process yields silica aerogels exhibiting very low bulk density and high specific surface area of 0.062 g/cm(3) and 520 m(2)/g, respectively. The average pore diameter and the cumulative pore volume varied from 4.5 to 12.1 nm and 0.58 to 1.58 cc/g, respectively. In addition, the aerogels are superhydrophobic with contact angle as high as 152 degrees. We anticipate that the new route of the monolithic silica aerogel production will greatly expand the commercial exploitation of these materials. (c) 2006 Elsevier Inc. All rights reserved.