SOLID-ON-SOLID MODEL APPLIED TO SURFACE PRESSURE OF BINARY SURFACTANTMIXTURES SPREAD AT THE AIR-WATER-INTERFACE

A theoretical approach is presented to relate the equilibrium surface pressure (ESP) of binary mixtures of water-insoluble surfactants to th e equilibrium surface pressures of the pure components. The approach i s based on the application of a two-dimensional (2D) solid-on-solid mo del for an exact computation of the surface pressure. The Hamiltonians describing the energetic cost for the creation of ''mixed'' interface s are constructed considering configurations with one random walk. The performed numerical computations use a single parameter for an evalua tion of the interfacial intermolecular interactions between like and u nlike molecules. The predictions of the 2D solid-on-solid model in the case of non-ideal mixing are compared with experimental results for E SP of two-component phospholipid-alkanoic acid surfactant mixtures.