Zholobenko Vladimir L, Khodakov Andrei Y, Impéror-Clerc Marianne, Durand Dominique, Grillo Isabelle
Department of Chemistry, Keele University, Staffordshire, ST5 5BG, United Kingdom.
Adv Colloid Interface Sci. 2008 Oct 1;142(1-2):67-74. doi: 10.1016/j.cis.2008.05.003. Epub 2008 Jun 4.
This work presents an overview of the data obtained for SBA-15 synthesis under the reaction conditions using synchrotron based small angle X-ray scattering and small angle neutron scattering. Three major stages in the synthesis of SBA-15 materials proceeding according to the cooperative self-assembly mechanism have been identified, and the structures of the intermediates species have been established. Our in situ time-resolved neutron scattering experiments demonstrate that only spherical micelles of the templating agent are present in the synthesis mixture during the first stage of the reaction. According to the neutron scattering and X-ray scattering data, in the second stage of the reaction the formation of hybrid organic-inorganic micelles is accompanied with the transformation from spherical to cylindrical micelles, which takes place before the precipitation of the ordered SBA-15 phase. During the third stage, these micelles aggregate into a two-dimensional hexagonal structure, confirming that the precipitation takes place as the result of self-assembly of the hybrid cylindrical micelles. As the synthesis proceeds, the voids between the cylinders are filled with the silicate species which undergo condensation reactions resulting in cross-linking and covalent bonding, leading to the formation of highly ordered SBA-15 mesostructure. This work demonstrates that valuable structural information can be obtained from X-ray and neutron scattering characterisation of complex systems containing periodic phases with d-spacing values up to 30 nm, and that both techniques are powerful means for in situ monitoring of the formation of nanostructured materials.
这项工作概述了在反应条件下使用基于同步加速器的小角X射线散射和小角中子散射获得的SBA - 15合成数据。已确定了按照协同自组装机制进行的SBA - 15材料合成中的三个主要阶段，并确定了中间物种的结构。我们的原位时间分辨中子散射实验表明，在反应的第一阶段，合成混合物中仅存在模板剂的球形胶束。根据中子散射和X射线散射数据，在反应的第二阶段，杂化有机 - 无机胶束的形成伴随着从球形胶束到圆柱形胶束的转变，这发生在有序SBA - 15相沉淀之前。在第三阶段，这些胶束聚集成二维六方结构，证实沉淀是杂化圆柱形胶束自组装的结果。随着合成的进行，圆柱之间的空隙被硅酸盐物种填充，这些物种发生缩合反应，导致交联和共价键合，从而形成高度有序的SBA - 15介观结构。这项工作表明，可以从对包含d间距值高达30 nm的周期性相的复杂系统进行X射线和中子散射表征中获得有价值的结构信息，并且这两种技术都是原位监测纳米结构材料形成的有力手段。
