Thermodynamic Study on Phase Transition in Adsorbed Film of Fluoroalkanol at the Hexane/Water Interface. 6. Pressure Effect on the Phase Transition in the Adsorbed Film of Alkanol and Fluoroalkanol Mixture

Takanori Takiue, Takayuki Toyomasu, Norihiro Ikeda, Makoto Aratono

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The phase transition in the adsorbed film of 1-icosanol (C20OH) and 1,1,2,2-tetrahydroheptadecafluorodecanol (FC10OH) mixture at the hexane/water interface was studied by measuring the pressure dependence of interfacial tension at a specific composition of FC10OH X2 = 0.280 and 298.15 K and evaluating the volume change of adsorption. By drawing the interfacial pressure π vs mean area per adsorbed molecule A curve, it was clarified that three types of first-order phase transitions (gaseous-expanded, expanded-FC10OH condensed, and FC10-OH condensed-C20OH condensed) take place in the adsorbed film. The phase transition from the FC10OH condensed to the C20OH condensed state was accompanied by a decrease of the volume change associated with adsorption Δν. By evaluating the partial molar volume change of adsorption, ν̄HiOi, and comparing its pressure dependence between the FC10OH condensed and C20OH condensed states, it was suggested that the pressure dependence of the partial molar volume is in the order of ∂νO2/∂p > ∂νO1/∂p > ∂ν̄H2/∂p ≈ ∂ν̄H2/∂p. Furthermore, it was found that the transition pressure πeq of the FC10OH condensed-C20OH condensed transition (second transition) increases and the corresponding one of the expanded-FC10OH condensed transition (first transition) decreases with increasing pressure. This difference was explained by means of the ν̄HiOi values at the phase transition point.

Original languageEnglish
Pages (from-to)6547-6553
Number of pages7
JournalJournal of Physical Chemistry B
Issue number31
Publication statusPublished - Aug 5 1999


All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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