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原位引入有机组分对氧化硅体系改性是合成有机-无机杂化硅材料的重要方法.利用原位的~(29)Si液体核磁,研究了甲醇为溶剂、氨水催化条件下的四乙氧基硅烷(TEOS)和二甲基二乙氧基硅烷(DDS)原位共水解的动力学过程.通过改变反应体系中氨和水的浓度,拟合出单体及中间产物浓度随时间的变化曲线,得到了TEOS和DDS各自的水解速率常数以及相应各反应物的反应级数.与单前驱体水解一致的是,在双前驱体系中TEOS和DDS自身的反应级数仍保持一级,但是氨和水的反应级数都有不同程度的增大.与单前驱体水解速率方程相比,混合体系中TEOS的水解速率常数增大.同时,DDS在双前驱体中比单前驱体中的水解速率常数有很大程度的减少.水解动力学表明,TEOS和DDS在双前驱体体系中显示出更平行的水解速率.利用固体~(29)Si MAS NMR,XPS及小角X射线散射(SAXS)手段对双前驱体体系研究得到的信息显示,碱催化条件下原位的TEOS水解中间物与DDS中间产物的原位共缩聚程度很弱.
In-situ incorporation of organic components into silica system is an important method for the synthesis of organic-inorganic hybrid silicon materials.Using in-situ (29) Si liquid nuclear magnetic resonance spectroscopy, the effects of methanol as solvent, (TEOS) and dimethyldiethoxysilane (DDS) in situ co-hydrolysis kinetic process by changing the concentration of ammonia and water in the reaction system to fit the monomer and intermediate concentration over time The hydrolysis rate constants of TEOS and DDS and the reaction orders of the corresponding reactants were obtained.Compared with the single-precursor hydrolysis, the reaction order of TEOS and DDS remained one order in the dual-precursor system, However, the reaction order of ammonia and water all increased to some extent.Compared with the single-precursor hydrolysis rate equation, the hydrolysis rate constant of TEOS increased in the mixed system.At the same time, The hydrolysis rate constants of the two precursors are greatly reduced.The kinetics of hydrolysis shows that TEOS and DDS show more parallel hydrolysis rate in the dual-precursor system.Using the solid-state (29) Si MAS NMR, XPS and small-angle X-ray scattering SAXS) means of dual precursor system obtained The information shows that the degree of in-situ co-condensation of the in situ TEOS hydrolyzate intermediate and DDS intermediate under base catalysis is weak.