On the hydrodynamics of a solvent-saturated lipid bilayer. I. Model of repulsion.

In two consecutive papers we study the stability of black lipid films against thermally induced hydrodynamic fluctuations. In the present part we develop a semiphenomenological theory of steric repulsion in these films. The model employs the statistical mechanical formulation of the van der Waals theory of simple liquid–vapor interfaces; it is based on the picture that upon diminishing the film thickness the adjacent interfacial layers start overlapping in the film center raising the degree of orientation of the hydrocarbon segments there. This causes a mutual repulsion of the two film surfaces. The general order parameter profile is found to depend on two parameters which can be determined from film compression measurements. [ABSTRACT FROM AUTHOR]