Deparment of Physics, Norwegian University of Science and Technology ,Høgskoleringen 5, 7491 Trondheim, Norway.
IMMM, UMR CNRS 6087, Université du Maine , Le Mans 72085 cedex 09, France.
ACS Appl Mater Interfaces. 2017 Jan 25;9(3):3093-3101. doi: 10.1021/acsami.6b12936. Epub 2017 Jan 11.
Surfactant templated silica thin films were self-assembled on solid substrates by dip-coating using a partially fluorinated surfactant R(EO) as the liquid crystal template. The aim was 2-fold: first we checked which composition in the phase diagram was corresponding to a 2D rectangular highly ordered crystalline phase and second we exposed the films to sc-CO to foster the removal of the surfactant. The films were characterized by in situ X-ray reflectivity (XRR) and grazing incidence small angle X-ray scattering (GISAXS) under CO pressure from 0 to 100 bar at 34 °C. GISAXS patterns reveal the formation of a 2-D rectangular structure at a molar ratio R(EO)/Si equal to 0.1. R(EO) micelles have a cylindrical shape, which have a core/shell structure ordered in a hexagonal system. The core contains the R part and the shell is a mixture of (EO) embedded in the silica matrix. We further evidence that the extraction of the template using supercritical carbon dioxide can be successfully achieved. This can be attributed to both the low solubility parameter of the surfactants and the fluorine and ethylene oxide CO-philic groups. The initial 2D rectangular structure was well preserved after depressurization of the cell and removal of the surfactant. We attribute the very high stability of the rinsed film to the large value of the wall thickness relatively to the small pore size.
表面活性剂模板二氧化硅薄膜通过使用部分氟化表面活性剂 R(EO) 作为液晶模板的浸涂在固体基底上自组装。目的有两个：首先，我们检查相图中的哪种组成对应于 2D 矩形高度有序的结晶相；其次，我们将薄膜暴露于超临界 CO 中以促进表面活性剂的去除。在 34°C 下，通过原位 X 射线反射率 (XRR) 和掠入射小角 X 射线散射 (GISAXS) 在从 0 到 100 巴的 CO 压力下对薄膜进行了表征。GISAXS 图案显示在摩尔比 R(EO)/Si 等于 0.1 时形成了 2-D 矩形结构。R(EO) 胶束具有圆柱形形状，其具有在六方系统中有序的核/壳结构。核包含 R 部分，壳是嵌入二氧化硅基质中的 (EO) 的混合物。我们进一步证明，使用超临界二氧化碳可以成功提取模板。这归因于表面活性剂的低溶解度参数以及氟和氧化亚乙基 CO 亲基团。在减压和去除表面活性剂后，初始的 2D 矩形结构得到了很好的保留。我们将冲洗后的薄膜的高稳定性归因于相对较小的孔径的较大壁厚值。
