Effects of reaction parameters on the preparation of thick silica gel films by an interfacial polymerization. 1. Effects of pH and type of catalyst

Abstract

The polymerization of different silicon precursors at the interface of two immiscible liquids (“organic” and “inorganic” phase) led to the formation of thick (up to 40 μm) and crack-free silica gel films. The pH of the “inorganic” phase and the type of catalyst strongly governed the rate of film formation along with the gel film properties. The preparation of thick and crack-free gel films within 24 hours of reaction time was possible for both acid-catalyzed and base-catalyzed systems in the vicinity of pH=2 and 11, respectively. The use of acetic acid as an catalyst led to gel films with a weight eight times higher than those prepared using HCl and HNO₃ catalysts. The weight of formic acid-catalyzed gel films was four times higher, and the weight of citric acid-catalyzed gel films was twice as high as the mineral acid-catalyzed gel films, respectively.