Dependence of drying technique on surface area and pore size for polyethylene glycol/tetramethoxysilicate hybrid gels

The effect of drying technique on the surface area and pore size of ethylene glycol/polyethylene glycol (PEG)/ tetramethoxysilicate hybrid gels is presented. Various molecular weight polyethylene glycols were added to acid-catalyzed solutions of tetramethoxysilane (TMOS) in methanol. The two drying techniques investigated were supercritical CO2 drying and conventional evaporation. Nitrogen adsorption was used to determine the surface area and pore radius. As the molecular weight of the polyethylene glycol increased, the pore size,of the gel increased, and the surface area decreased. For gels with no polymer additive, both the surface area and pore size of the gels is dependent on the drying method. However, when the various polymers were added, this difference became insignificant, indicating that the polymer assists in opening the pore structure and prevention of syneresis. (C) 2003 Elsevier Science B.V. All rights reserved.