Porosity of resorcinol-formaldehyde organic and carbon aerogels exchanged and dried with supercritical organic solvents

Organic and carbon aerogels have been prepared from resorcinol-formaldehyde resin diluted with various amounts of water. Water was exchanged by acetone or ethanol, and the gels were subsequently dried with supercritical acetone or with supercritical ethanol. We showed that the nature of the solvent with which water was exchanged only had a minor impact on the porosity of the resultant aerogels. In contrast, the same solvents used as drying fluids in the supercritical state led to significant differences, but only in the case of diluted gels. When the initial dilution was low, similar results were indeed obtained with both solvents. Ethanol was shown to lead to higher shrinkages and higher bulk densities than acetone. A higher chemical degradation of the resin during the drying process was also observed when ethanol was used.