Surface Freezing and Molecular Miscibility of Binary Alkane-Alkane and Fluoroalkane-Alkane Liquid Mixtures
Surface Freezing and Molecular Miscibility of Binary Alkane-Alkane and Fluoroalkane-Alkane Liquid Mixtures
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二元烷烃-烷烃和氟烷烃-烷烃液体混合物的表面冷冻和分子混溶性
DOI：
10.1021/jp406431m
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发表时间：
2014
期刊：
影响因子：
3.3
通讯作者：
M. Aratono
中科院分区：
文献类型：
--
作者：
T. Takiu;M. Shimasaki;M. Tsuura;H. Sakamoto;H. Matsubara;M. Aratono
用表面张力和外反射红外光谱(ERA-FTIR)研究了液体正十七烷(C17)-正十八烷(C18)和1-全氟正十八烷(F8H10)-C18混合物的表面冻结行为。所有纯液体的表面张力-温度曲线在T_s处都有一个尖锐的断点，对应于表面液体(SL)-SF的转变。表面形成的熵非常负，表明SF层具有良好的有序结构。SF态的ERA-FTIR谱表明，C18分子在固态中密集堆积，而F8H10的碳氢(HC)部分由于截面积的不同，其碳氢(HC)部分的堆积略松于氟碳(FC)部分。在C17-C18混合物中，所有的体组分都存在SL-SF转变。表面组成的估算表明，两个组分在SL和SF状态下都是相容的。表面的超额熵在两种状态下几乎为零，因此，可以得出结论，这两种成分在表面几乎理想地混合在一起。另一方面，在F8H10-C18体系的情况下，SL层富含F8H10，与主体液体相比，表面张力低于C18。SF态的表面组成几乎为零或1，表明F8H10和C18分子实际上是不相容的，这主要是由于不同组分之间的弱相互作用。此外，SL层中的负超额熵表明F8H10分子在表面形成了磁区。
The surface freezing (SF) of liquidn-heptadecane (C17)–n-octadecane (C18) and 1-perfluorooctyl decane (F8H10)–C18mixtures were studied by surface tension and external reflection absorption FTIR (ERA-FTIR) measurements. The surface tension versus temperature curves of all pure liquids show a sharp break point atTscorresponding to a surface liquid (SL)–SF transition. The entropy of surface formation is very negative, indicating a well-ordered structure of the SF layer. The ERA-FTIR spectra in the SF state suggested that the C18molecules are densely packed in the solid state, while the packing of the hydrocarbon (HC) part of F8H10is a little looser than the fluorocarbon (FC) part because of the difference in the cross-sectional area. In the C17–C18mixture, the SL–SF transition was found at all bulk compositions. The estimation of the surface composition suggested that two components are miscible both in SL and SF states. The excess entropy of the surface is almost zero in both states, and thus, it was concluded that the two components are mixed almost ideally at the surface. In the case of the F8H10–C18system, on the other hand, the SL layer is enriched in F8H10with lower surface tension than C18compared to bulk liquid. The surface composition in the SF state is almost zero or unity, indicating that F8H10and C18molecules are practically immiscible mainly due to the weak interaction between different components. Furthermore, the negative excess entropy in the SL layer suggests domain formation of F8H10molecules at the surface.