Surface freezing and molecular miscibility of binary alkane-alkane and fluoroalkane-alkane liquid mixtures

Takanori Takiue, Mayuko Shimasaki, Miyako Tsuura, Hiroyasu Sakamoto, Hiroki Matsubara, Makoto Aratono

研究成果: Contribution to journalArticle査読

5 被引用数 (Scopus)

抄録

The surface freezing (SF) of liquid n-heptadecane (C17)-n- octadecane (C18) and 1-perfluorooctyl decane (F8H 10)-C18 mixtures 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 at Ts corresponding 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 C 18 molecules are densely packed in the solid state, while the packing of the hydrocarbon (HC) part of F8H10 is a little looser than the fluorocarbon (FC) part because of the difference in the cross-sectional area. In the C17-C18 mixture, 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-C18 system, on the other hand, the SL layer is enriched in F8H10 with lower surface tension than C18 compared to bulk liquid. The surface composition in the SF state is almost zero or unity, indicating that F8H10 and C18 molecules 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 F8H10 molecules at the surface.

本文言語英語
ページ(範囲)1519-1526
ページ数8
ジャーナルJournal of Physical Chemistry B
118
6
DOI
出版ステータス出版済み - 2 13 2014

All Science Journal Classification (ASJC) codes

  • 物理化学および理論化学
  • 表面、皮膜および薄膜
  • 材料化学

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