Phase transition of the adsorbed film of 1,1,2,2-tetrahydroperfluorododecanol at the hexane/water interface

The interfacial tension of the hexane solution of 1,1,2,2-tetrahydroperfluorododecanol (FC₁₂OH) against water was measured as a function of temperature and concentration under atmospheric pressure. The break point indicating a phase transition of the adsorbed film was seen on the interfacial tension vs temperature and concentration curves. The thermodynamic quantity changes associated with the adsorption were evaluated by applying thermodynamic relations; they were observed to change discontinuously at the transition point. By comparing this behavior with that of tetradecanol and octadecanol, the adsorbed film of FC₁₂OH was concluded to be transformed from a gaseous to a condensed state.