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, ν̄Hi-νOi, 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 ν̄Hi-νOi values at the phase transition point.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry