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Determination of Acid-Base Properties of Silicas by Inverse Gas Chromatography : Variation with Surface Treatment

The specific component of the free energy of adsorption, G A , of untreated crystalline and fused silica, and four types of silane coupling agents-treated fused silicas, were estimated by the inverse gas chromatography (IGC) method, using the adsorption of several polar and nonpolar probes on their surfaces at various measuring temperatures. The acid-base properties of the untreated and surface-treated silicas were quantified by their KA and KD parameters, reflecting the ability of the surface to act as an electron acceptor and donor, respectively. Acidic components were detected on the untreated crystalline and fused silica surfaces, but the surface properties of the fused silicas surface-treated with -glycidoxy propyl trimethoxy silane (GMS) and -amino propyl triethoxy silane (AES) were slightly basic, and those of the fused silicas surface-treated with -methacryloxy propyl trimethoxy silane (MTMS) and -mercapto propyl trimethoxy silane (MCMS) were amphoteric. [doi:10.2320/matertrans.MER2007076]