A new route to aerogels: Monolithic silica cryogels

We have explored several different gel syntheses and drying procedures for producing silica cryogels with similar properties to those of silica aerogels, particularly in terms of monolithicity, density, porosity and surface area. These materials could be a suitable alternative to silica aerogels and ambigels. Some successful preparation methods are presented and properties of the corresponding cryogels are discussed, including comparison of these materials to supercritically dried products and an assessment of the effects of the experimental variables in the preparation process on the properties of the resultant cryogels. Two routes for the preparation of cryogels are highlighted, one of which is especially attractive as it has the advantage (compared to the known syntheses of APD aerogels) of not requiring any solvent exchange step. (C) 2011 Elsevier B.V. All rights reserved.