Controlling the shape and alignment of mesopores by confinement in colloidal crystals: designer pathways to silica monoliths with hierarchical porosity.
Controlling the shape and alignment of mesopores by confinement in colloidal crystals: designer pathways to silica monoliths with hierarchical porosity.
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DOI：
10.1021/la062969s
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发表时间：
2007-01
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影响因子：
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通讯作者：
Fan Li;Zhiyong Wang;Nicholas S. Ergang;C. Fyfe;A. Stein
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文献类型：
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作者：
Fan Li;Zhiyong Wang;Nicholas S. Ergang;C. Fyfe;A. Stein
通过双模板法合成了含有周期性大孔和具有良好控制结构的中孔的分级结构二氧化硅的单片。胶体晶体模板与聚（甲基丙烯酸甲酯）球的紧密堆积阵列产生规则的，高度互连的大孔直径为几百纳米，和模板与非离子表面活性剂产生中孔（2.5-5.1 nm孔径）的大孔壁。根据表面活性剂、助表面活性剂和加工条件的选择，可以在二氧化硅骨架内实现几种不同的介观结构。在胶体晶体模板的三维（3D）限制中，用表面活性剂Brij 56（C16 H33（OCH 2CH 2）nOH（n约10）和十二烷作为助表面活性剂产生蠕虫状通道、立方（Pm 3 n）或二维（2D）六边形（P6 mm）介观结构。在2D六边形结构中，通道垂直于聚合物球体取向，从而通过二氧化硅壁连接相邻的大孔。当使用聚合物表面活性剂Pluronic P123（EO20 PO 70 EO20）时，该取向与平行于胶乳球的通道排列形成对比。的高分辨率的3D透射电子显微镜，扫描电子显微镜，小角X射线散射，和氮吸附测量的基础上，详细描述的整料的结构和纹理特性的合成参数的函数。通过考虑介观结构相对于胶乳模板中的间隙空间、界面相互作用、熵效应和结构挫折的相对尺寸来解释这些二氧化硅-表面活性剂系统在3D限制中的介观结构的控制。
Monolithic pieces of hierarchically structured silica, containing both periodic macropores and mesopores with well-controlled architecture, are synthesized by dual templating methods. Colloidal crystal templating with close-packed arrays of poly(methyl methacrylate) spheres yields regular, highly interconnected macropores a few hundred nanometers in diameter, and templating with nonionic surfactants produces mesoporosity (2.5-5.1 nm pore diameters) in the macropore walls. Several distinct mesostructures can be achieved within the silica skeleton, depending on the choice of surfactant, co-surfactant, and processing conditions. In the three-dimensional (3D) confinement of the colloidal crystal template, wormlike channels, cubic (Pm3n), or two-dimensional (2D) hexagonal (P6mm) mesostructures are produced with the surfactant Brij 56 (C16H33(OCH2CH2)nOH (n approximately 10) and dodecane as cosurfactant. In the 2D hexagonal structure, channels are oriented perpendicular to the polymer spheres, thereby connecting adjacent macropores through the silica walls. This orientation contrasts with channel alignment parallel to latex spheres when the polymeric surfactant Pluronic P123 (EO20PO70EO20) is used. On the basis of high-resolution 3D transmission electron microscopy, scanning electron microscopy, small-angle X-ray scattering, and nitrogen sorption measurements, structural and textural properties of the monoliths are described in detail as a function of the synthesis parameters. The control over the mesoarchitecture of these silica-surfactant systems in 3D confinement is explained by considering the relative dimensions of the mesostructures with respect to the interstitial space in the latex template, interfacial interactions, entropic effects, and structural frustration.