Mizukami Masashi, Nakagawa Yasuhiro, Kurihara Kazue
Institute of Multidisciplinary Research for Advanced Material, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan.
Langmuir. 2005 Oct 11;21(21):9402-5. doi: 10.1021/la0512190.
Recently, we have succeeded in identifying the structure of the adsorption layer of ethanol on a silica surface in cyclohexane to be a hydrogen-bonded linear aggregate (polymer), which we call a surface molecular macrocluster. In this work, we studied the effect of the miscibility of liquids on the formation of the surface molecular macroclusters for confirming that this is a surface induced phenomenon. We investigated the interaction and the structure of methanol adsorbed on a silica surface in methanol-cyclohexane binary liquids by a combination of colloidal probe atomic force microscopy, adsorption excess isotherm measurement, and FTIR spectroscopy using the attenuated total reflection (ATR) mode, and compared the results with those of the ethanol-cyclohexane and 1-propanol-cyclohexane binary liquids. The former system is immiscible at methanol concentrations of ca. 8-90 mol %, and the latter two are miscible at any composition. At 0.03 mol % methanol, which is far from the critical concentration for the phase separation, the contact of the methanol macrocluster layers formed on the silica surface brought about the attraction from a distance of 42 +/- 5 nm which was similar to that observed in ethanol-cyclohexane. At a methanol concentration of 9.0 mol %, above bulk phase separation, completely different force profiles were observed. These results demonstrated that the molecular macrocluster formation was different from the wetting induced by the bulk.
最近，我们成功确定了环己烷中乙醇在二氧化硅表面吸附层的结构为氢键连接的线性聚集体（聚合物），我们将其称为表面分子大聚集体。在这项工作中，我们研究了液体混溶性对表面分子大聚集体形成的影响，以确认这是一种表面诱导现象。我们通过胶体探针原子力显微镜、吸附过量等温线测量以及使用衰减全反射（ATR）模式的傅里叶变换红外光谱（FTIR）相结合的方法，研究了甲醇 - 环己烷二元液体中吸附在二氧化硅表面的甲醇的相互作用和结构，并将结果与乙醇 - 环己烷和1 - 丙醇 - 环己烷二元液体的结果进行了比较。前一个体系在甲醇浓度约为8 - 90 mol%时互不相溶，而后两个体系在任何组成下都互溶。在远离相分离临界浓度的0.03 mol%甲醇浓度下，二氧化硅表面形成的甲醇大聚集体层之间的接触在42 +/- 5 nm的距离处产生了吸引力，这与在乙醇 - 环己烷中观察到的情况相似。在9.0 mol%的甲醇浓度下，高于本体相分离浓度时，观察到了完全不同的力分布。这些结果表明，分子大聚集体的形成与本体诱导的润湿不同。
