有机氯硅烷修饰的介孔SBA-15及其疏水性

Study on Mesoporous SBA-15 Modified by Organochlorosilane and Its Hydrophobicity

在非极性溶剂(甲苯)中,用三甲基氯硅烷和苯基二甲基氯硅烷对全硅介孔分子筛SBA-15进行了表面修饰。利用傅里叶变换红外光谱(FT IR)、X射线粉末衍射(XRD)和低温N2吸附-脱附等手段对样品进行了结构分析;并通过测定样品在水或正己烷饱和蒸汽中的吸附量,研究了它们的疏水性。结果表明,表面改性后的SBA-15仍保持完好的介孔结构,由于有机官能团接枝在SBA-15的内表面,占据了孔道内部空间,使其比表面积、孔容和孔径都减小。样品的疏水性与有机硅烷试剂的分子结构有关,不同硅烷试剂会引起分子筛表面极性不同。脂肪族的三甲基氯硅烷(TMCS)分子较芳香族的苯基二甲基氯硅烷分子小,空间位阻较小,较易降低样品的表面极性,降低了吸附水的可能性,表现出较好的疏水性。

The surface of pure silica mesoporous molecular sieve（SBA-15） was modified by trimethylchlorosilane（TMCS） and phenyldimethyldichlorosilane（PDMCS） in apolar solvent（toluene）.The samples were characterized by IR,XRD and N2 adsorption-desorption.Experimental results showed that the original mesoporous structure of samples remained intact after modification.The IR spectra demonstrated that the organic groups had successfully grafted onto the surface of SBA-15,but the grafted samples showed a lower BET surface area and pore volume and smaller pore size.The hydrophobicity of modified samples was measured through comparison of the adsorption capacity for the vapour of water or n-hexane.The degree of hydrophobicity is related to the structure of silylating agents.The different functional silanes were proved to show different effect on surface polarity.The post-grafting silylation with aliphatic silane（TMCS） reduced the surface polarity better than that with aromatic silane（PDMCS） which was possibly caused by less steric hindrance.The enhancement of surface hydrophobicity was obtained more effectively from the silylation with samller silane molecules on SBA-15.