単脂環アルコールで処理したシリカゲルの表面特性

抄録

The silica gels were treated with the hexane solutions of several kinds of alicyclic alcohols at the critical point of n-hexane in an autoclave. After completion of reaction the vapor of both unreacted alcohol and water was vented out of autoclave to avoid the contact of these vapors with the treated silica gels. These gels showed the hydrophobic and lyophilic nature, since they were preferentially dispersed into oil phase when dispersed into the mixture of disperse media which are immiscible with each other like oil and water. All of these properties, such as the numbers of surface group obtained from their carbon contents, the relationship between their argon surface areas and numbers of surface group and the relationship between the inner surface area composed of the unreacted silanol in the micropores covered by a surface group and the molecular cross sectional areas of alcohols used, showed the same trends as reported previously. Furthermore the characteristic absorption due to surface groups observed in the infrared absorption spectra of the treated silica gels indicated that the surface groups were composed of alcoxy group of alcohols used. The ratio of characteristic absorption coefficient due to the surface group and that at 800cm^-1 due to skeltal vibration of the treated silica gel, _??_Si-O-Si_??_ follows the Lambert-Beer's law against the ratio of molar concentration of carbon and that of silica in KBr disc. Since the molar extinction coefficient of absorption due to the surface group showed a constant value against the number of surface groups, the surface group of silica gels treated with alicyclic alcohol was not the physisorbed nor chemisorbed alcohol, but chemically bonded as an alcoxy group to Si on SiO₂.