EFFECTS OF DIMETHYLDIETHOXYSILANE ADDITION ON TETRAETHYLORTHOSILICATE SOL-GEL PROCESS

Abstract

The effect of the addition of dimethyldiethoxysilane (DDS) on the hydrolysis-condensation of tetraethylorthosilicate (TEOS) was investigated by varying the amount of DDS added to TEOS solutions (0-67% in more fraction) and the addition-time of DDS. The addition of a small amount of DDS remarkably decreased the gelation time of acid solutions of TEOS because of the rapid reaction of DDS and the suppression of the cyclic species from TEOS. A further increase in DDS content, however, made the gelation time longer, because the decrease of the average functionality and the increase of the cyclic species prevented the formation of a siloxane network. The lower degree of cross-linking and the release of cyclic species influenced the weight loss of gels in the drying process.