Elllects of mixtures of alkanes on the bending rigidity constant k of AOT monolayers at the planar oil-water interface

We have studied the phase diagrams of brine/oil/AOT mixtures in which the oils are mixtures of octane and tetradecane and the amount of AOT is small. In addition, the properties of the AOT monolayer at the brine/oil interface as a function of the volume fraction φ of tetradecane in the oil have been measured. The values of the interfacial tension and the phase diagram behaviour show that the Equivalent Alkane Carbon Number concept is valid in these systems, where a small change of φ induces a large change in the phase diagram. In addition we show that this concept applies to the bending elastic modulus K and probably to the saddle splay modulus.