Effects of dimethyldiethoxysilane addition on the sol–gel process of tetraethylorthosilicate

The effects of dimethyldiethoxysilane (DDS) addition on the sol–gel process of tetraethylorthosilicate (TEOS) were investigated by varying the addition-time of DDS to acid-catalyzed TEOS solutions in different water contents. At a low water content, the solution is transparent until gelation takes place, while at a high water content, phase separation occurs and leads to hydrophobic particles which, according to scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) and thermogravimetric (TG) analysis, show different morphology and thermal behavior. The reaction between TEOS and DDS in different water contents and the structure of final polymers are discussed.