小角x射线散射方法研究甲基改性氧化硅干凝胶的孔结构

以正硅酸乙酯［Si(OC2H5)4，TEOS］为前驱体制备SiO2悬浮液，分别以甲基三乙氧基硅烷［CH3Si(OC2H5)3，MTES］和二甲基二乙氧基硅烷［(CH3)2Si(OC2H5)2，DDS］为前驱体制备硅氧烷聚合物溶液，通过混合法得到两种不同的甲基改性氧化硅凝胶-测量了凝胶的散射强度，计算了凝胶的孔径分布、平均孔径DSAXS、界面层厚度E等参数，结合氮气吸附实验，分析了凝胶的孔结构-发现SiO2一次簇团被MTES聚合物或DDS聚合物连接为二次簇团时产生微孔，同时甲基随聚合物连接于凝胶骨架上形成与 关键词： 小角x射线散射 甲基改性氧化硅 干凝胶 孔结构

Pore structures of methyl-modified silica xerogels by small angle x-ray scattering

Two kinds of methyl-modified silica xerogels were prepared by mixing SiO2 colloidal suspension deriving from basic-catalyzed hydrolysis of TEOS (tetraethoxysilane) and siloxane polymer solution prepared from acid-catalyzed hydrolysis of MTES (methyltriethoxysilane) or DDS (dimethyldiethoxysilane). The xerogels were tested at the small angle x-ray scattering (SAXS) station of Beijing Synchrotron Radiation Facility. The distribution of pore size, the average size of pores DSAXS, and the thickness of interface layer E were calculated. With the aid of nitrogen adsorption measurement, the pore structure was analyzed. Some micropores were found to be produced in methyl-modified SiO2 xerogels while second-aggregates were constructed through connecting first-aggregates with siloxane polymer of MTES or of DDS. At the same time, methyl groups were attached to the bone of SiO2 clusters and become an interface layer between bone and pore. The interface layer have effects on both pore size and the adsorption of nitrogen in methyl-modified xerogels. Through transmission electron microscope we confirmed that the pore structures of the xerogels were affected strongly by the two different siloxane polymers. SAXS is a powerful technique to study pore structure of xerogel system.