Multilayer Formation of the Fluoroalkanol -〓-Hydrogenated Fluorocarbon Mixture at theHexane/Water Interface Studied by Interfacial Tensiometry and X-ray Reflection
Multilayer Formation of the Fluoroalkanol -〓-Hydrogenated Fluorocarbon Mixture at theHexane/Water Interface Studied by Interfacial Tensiometry and X-ray Reflection
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通过界面张力测定和X射线反射研究氟烷醇-氢化氟碳混合物在己烷/水界面处的多层形成
DOI：
10.1021/jp309589f
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
M. Aratono
中科院分区：
文献类型：
--
作者：
T. Takiue;T. Tottori;K. Tatsuta;H. Matsubara;K. Nitta;H. Tanida;T. Uruga;M. Aratono
从吸附膜中分子间相互作用和分子混溶性的角度研究了己烷/水界面上氟碳化合物的新型多层形成。采用两种混合体系：1H，1H，2H，2H-全氟十二烷醇（FC12OH）–1H-全氟癸烷（HFC10）（系统A）和1-二十烷醇（C20OH）–HFC10（系统B）。在大气压、298.15K下测量己烷溶液和水之间的界面张力γ作为混合物中HFC10的总浓度和组成X2的函数。 X 射线反射率 (XR) 测量是在 SPring-8 的 BL37XU 上进行的，作为散射矢量 Qz 的函数。在这两个系统中，除纯HFC10系统外，γ vsm曲线在低浓度下都有一个断裂，这对应于系统A的气态-冷凝单层转变和系统B的膨胀-冷凝单层转变。两个系统之间的显着差异是，系统A的有限本体组成范围（0.45≤X2≤0.9）内的曲线在接近溶解度极限的高浓度下显示出另一个断裂。该断点以上的总界面密度约为 7-11 μmol m-2，表明自发分子堆积形成多层。凝聚单分子层中的吸附相图表明，HFC10 的膜组成在系统 B 中为负值，但在系统 A 中当 X2≥ 0.45 以上时肯定为正值。这清楚地表明，在凝聚单分子层中，HFC10 分子与 FC12OH 互溶，但与 C20OH 不互溶。因此，HFC10 与 FC12OH 在稠合单层中的混合可能会诱导多层形成。系统 A 的凝聚单层中由菲涅耳反射率 R/RFvsQzplot 归一化的 X 射线反射率通过具有均匀电子密度和厚度的单板模型进行拟合。电子密度分布几乎与纯FC12OH体系相同。另一方面，多层中的图与具有不同电子密度和厚度的两板模型吻合良好。电子密度分布表明，多层结构由两层组成，其中一层的电子密度略高于本体己烷相，下层的电子密度与凝聚的FC12OH单层几乎相同。
Novel multilayer formation of fluorocarbon compounds at the hexane/water interface was investigated from the viewpoint of intermolecular interaction and miscibility of molecules in the adsorbed film. The two kinds of mixed systems were employed: 1H,1H,2H,2H-perfluorododecanol (FC12OH)–1H-perfluorodecane (HFC10) (System A) and 1-icosanol (C20OH)–HFC10 (System B). The interfacial tension γ between the hexane solution and water was measured as a function of total concentrationmand the composition of HFC10 in the mixtureX2at 298.15 K under atmospheric pressure. X-ray reflectivity (XR) measurement was performed at BL37XU in SPring-8 as a function of scattering vectorQz. In both systems, the γ vsmcurves except for the pure HFC10 system have a break at low concentrations, which corresponds to the gaseous–condensed monolayer transition for System A and the expanded–condensed monolayer for System B. The remarkable difference between the two systems was that the curves in a limited bulk composition range (0.45 ≤X2≤ 0.9) of System A show another break at high concentrations close to the solubility limit. The total interfacial density above this break point was around 7–11 μmol m–2, suggesting the spontaneous molecular piling to form a multilayer. The phase diagrams of adsorption in the condensed monolayer indicated that the film composition of HFC10 is negative in System B but definitely positive aboveX2≥ 0.45 in System A. This clearly shows that HFC10 molecules are miscible with FC12OH but immiscible with C20OH in the condensed monolayer. Thus, it is likely that the mixing of HFC10 with FC12OH in the condensed monolayer induces multilayer formation. The X-ray reflectivity normalized by Fresnel reflectivityR/RFvsQzplot in the condensed monolayer of System A was fitted by a one-slab model with uniform electron density and thickness. The electron density profile was almost the same as that of the pure FC12OH system. The plot in the multilayer, on the other hand, was fitted well by the two-slab model with different electron densities and thicknesses. The electron density profile showed that the multilayer consists of two layers, one of which has slightly higher electron density than the bulk hexane phase and piles on the lower layer with almost the same electron density as the condensed FC12OH monolayer.