Mixed adsorption layers at the aqueous CnTAB solution/hexane vapour interface

Surface active molecules, which are amphiphilic in aqueous solutions, have different properties at water/air and water/oil interfaces. However, their behaviour at water/oil vapour interfaces is still unknown and requires further investigations. The adsorption behaviour of the members of the homologous series CnTAB at their aqueous solution/hexane vapour interface is studied using the drop profile analysis method. The data thus obtained are compared with results obtained earlier for the solution/air and solution/liquid hexane interfaces. The competitive adsorption of the components from both phases onto the interface is shown to take place, resulting in a significant enhancement of the CnTAB adsorption as compared with that at the solution/air interface. The theoretical model of the mixed adsorption monolayer developed earlier, which assumes the intermolecular interaction within the adsorption layer, is shown to be capable for the quantitative description of the observed phenomenon.