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.　(c)　2006　Elsevier　B.V.　All　rights　reserved.