A phase transition of the adsorbed layer: High pressure effect on fatty alcohol adsorption at an oil–water interface

Measurement of the interfacial tension of fatty alcohol solutions permits determination of the amount of amphiphile adsorbed. This amount varies with both pressure and concentration. At some critical value, the interfacial solution splits into two phases. In the dilute phase, the adsorbed molecules are solvated by the oil whereas in the condensed phase there is no solvent interspersed between the aliphatic chains. A thermodynamical analysis of this two-dimensional phase transition is given assuming the interfacial solution to be regular.