PREPARATION OF TRANSPARENT METHYL-MODIFIED SILICA-GEL

The hydrolysis and polymerization of methyltriethoxysilane (MTES) in the absence of solvents have been investigated. It was found that the resultant ethanol favored the formation of crystalline precipitates, (CH3SiO3/2)(8). Transparent CH3SiO3/2-SiO2 gels were prepared by a two-step method. MTES and tetraethoxysilane (TEOS) were partially hydrolyzed and some of the resultant ethanol was evaporated. Then, the water for the further hydrolysis reaction was added. After keeping the samples in closed vessels at 50 degrees C for 30 min, the gels were formed under open conditions. The infrared spectra of the gels thus obtained indicated that they become hydrophobic with the introduction of the methyl groups. The difference in the polymerization behaviors of methyltriethoxysilane and tetraethoxysilane is discussed.