The interfacial tension γ of the hexane solution of a mixture of 1,1,2,2-tetrahydroheptadecafluorodecanol (FC10OH) and 1,1,2,2-tetrahydrohenicosafluorododecanol (FC12OH) against water was measured as a function of the total molality m and composition of FC12OH X2 at 298.15 K under atmospheric pressure. The γ vs m curve has one or two distinct break points depending on X2. By plotting the γ and m values at the break points and drawing the interfacial pressure π vs mean area per adsorbed molecule A curves, it was suggested that the triple point of adsorbed film, at which the three kinds of states (gaseous, expanded, and condensed states) coexist simultaneously, exists at a middle composition. The phase diagrams of adsorption (PDA) were constructed and the excess Gibbs energy of adsorption gH,E was calculated to examine the miscibility of FC10OH and FC12OH molecules in the adsorbed film. It was found that these alcohols mix almost ideally both in the gaseous and expanded states and nonideally in the condensed state. Furthermore, the mixing of FC10OH and FC12OH in the condensed film, was accompanied by a positive gH,E value. This suggests that the difference in the magnitude of mutual interaction between the same species affects appreciably the miscibility of molecules in the condensed state where the adsorbed molecules are assumed to be closely packed and arranged regularly.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry