Intermolecular forces in monolayers at air/water interfaces

Abstract

Two-dimensional second virial coefficients for dilute lipid monolayers at air-water interfaces have been calculated from published isotherms. A reasonable fit to these coefficients is obtained by using Salem's estimates of the pair potentials for parallel straight hydrocarbon chains lying flat on the water surface. Chain coiling or flexing on close approach of two molecules seems to be small. Attempts to improve the fit with multibody corrections from the effect of the bulk water phase on the chain pair potentials using the form suggested by Sinanoglu and Pitzer were not helpful.