Highly swellable sol–gels prepared by chemical modification of silanol groups prior to drying

Abstract

Sol–gel materials that swell six times their dried volume when placed in organic solvents were prepared using the bridged silsesquioxane bis(trimethoxysilyethyl)benzene through base catalysis by tetrabutyl ammonium fluoride. Prior to drying the gels, water and catalyst were rinsed from the solvated matrix and residual silanol groups were derivatized with a chlorosilane (R–Si(CH3)2Cl). The swelling behavior was completely reversible when the materials are dried at elevated temperature. Swelling is highly dependent on the processing conditions, including the choice of solvent and catalyst. There is no preferential adsorption of solute molecules to swelled sol–gels despite the diversity of chlorosilanes used to derivatize the materials.