Structural and textural evolution of dimethyl-modified silica xerogels

A series of dimethyl-modified silica xerogels with different dimethyl contents were prepared by one-step hydrolysis and co-condensation from tetraethyloxysilane (TEOS) and dimethyldiethoxysilane (DEOS) containing precursor. The structural and textural evolution was traced by FT-IR spectroscopy, nitrogen absorption, scanning electron microscopy (SEM), transmittance electrical microscope (TEM), UV-Vis spectroscopy and thermogravimetric analysis (TGA). The addition of dimethyl groups can greatly reduce the pore size distribution of the resulted sample, while the 30% DEOS-70% TEOS sample is the most textural compact and therefore the most optical transparent. FT-IR and TGA results show that the samples are less hydroxygen containing owing to the hydrophobicity of the dimethyl groups.