The adsorption of 1H,1H,10H,10H-perfluorodecane-1,10-diol (FC₁₀diol) at the hexane/water interface was investigated by the measurement of temperature dependence of interfacial tension and the thermodynamic data analysis in order to know the effect of two hydroxyl groups at both ends of the hydrophobic chain and the rigidity of the hydrophobic chain on the adsorption of fluorocarbon alcohol at the interface. The curves of interfacial tension versus temperature and concentration show break points corresponding to the phase transitions in the adsorbed FC₁₀diol film. The interfacial pressure versus mean area per adsorbed molecule curve shows three kinds of states connected by two discontinuous changes. The area value after the first phase transition is very close to the calculated cross-sectional area of the FC₁₀diol molecule along its major axis, and thus the FC₁₀diol molecules form a condensed monolayer with molecular orientation parallel to the interface. Another noticeable point is that the value after the second phase transition point decreases furthermore to 0.12 nm², which is much smaller than the cross-sectional area of the fluorocarbon chain, 0.28 nm², with increasing interfacial pressure. This suggests that FC₁₀diol molecules pile spontaneously and successively form a multilayer above the second phase transition. Furthermore, the partial molar entropy and energy change of adsorption in the expanded and condensed states were evaluated and compared to those of 1H,1H,2H,2H-perfluorodecanol (TFC₁₀OH), which orients almost perpendicular to the interface. In addition to the contact of two hydroxyl groups with hexane in the bulk solution, the results are explained by the dependence of partial molar entropy and energy at the interface on the following factors resulting from the parallel orientation of FC₁₀diol at the interface; (a) hydrogen bonding of two hydroxyl groups with water molecules, (b) hydrogen bonding between two hydroxyl groups facing each other, and (c) the fluorocarbon chain−water contact. The adsorbed FC₁₀diol film is stabilized by factors a and b, which overwhelm the energetic disadvantage caused by factor c. Furthermore, the entropy change of adsorption Δs in the multilayer is compared to the Δs_cal calculated on the assumption that the condensed monolayer piles to form the multilayer. It was suggested that FC₁₀diol molecules are not so densely packed in the multilayer compared to the first condensed monolayer and therefore the multilayer is not simply formed by the piling of condensed monolayers.

中文翻译：

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1H，1H，10H，10H-全氟癸烷-1,10-二醇在己烷/水界面的分子取向和多层形成 温度对氟代链烷二醇吸附的影响

通过测量界面张力的温度依赖性和热力学数据分析，研究了1H，1H，10H，10H-全氟癸烷-1,10-二醇（FC ₁₀二醇）在己烷/水界面的吸附。疏水链两端的两个羟基和疏水链的刚度对氟碳醇在界面上的吸附的影响。界面张力与温度和浓度的关系曲线显示了对应于吸附的FC _10中的相变的断点二醇膜。界面压力与每个吸附分子的平均面积的关系曲线显示了通过两种不连续变化而联系在一起的三种状态。第一次相变后的面积值非常接近FC ₁₀二醇分子沿其长轴的计算截面积，因此FC ₁₀二醇分子形成分子方向平行于界面的缩合单分子层。另一个值得注意的点是，随着界面压力的增加，第二相变点之后的值进一步减小至0.12 nm ²，该值大大小于碳氟化合物链的横截面积0.28 nm ²。这表明FC ₁₀二醇分子自发地堆积并在第二相变上方连续形成多层。此外，评估了在膨胀和冷凝状态下的部分摩尔摩尔熵和吸附能变化，并将其与几乎垂直于界面取向的1H，1H，2H，2H-全氟癸醇（TFC ₁₀ OH）进行比较。除了本体溶液中两个羟基与己烷的接触之外，结果还通过界面上的部分摩尔熵和能量与FC ₁₀平行取向产生的以下因素的相关性来解释界面处的二醇；（a）两个羟基与水分子的氢键结合；（b）彼此面对的两个羟基之间的氢键结合；（c）碳氟链与水的接触。吸附的FC ₁₀二醇薄膜通过因子a和b稳定，这克服了因子c导致的能量不足。此外，吸附Δ熵变小号在多层是相对于Δ小号_CAL，前提是将冷凝单层桩以形成多层计算。提出与第一缩合单层相比，FC ₁₀二醇分子在多层中的密度不是很高，因此不能简单地通过堆叠缩合单层来形成多层。