The role of repulsive hydration forces on the stability of aqueous black films. Application to vesicle fusion

Abstract

A model of an aqueous black film is proposed for investigating the influence of repulsive hydration forces on the film's dynamic stability. Attractive forces (van der Waals) and repulsive forces (electrical and hydration) are treated as body forces in the equation of motion. The hydration repulsion is due to the work needed to remove water molecules from hydrophilic surfaces at small film thicknesses and is described by an exponentially decaying interaction potential. A linear stability analysis is performed for a symmetrical black film. The two modes of vibration (bending and squeezing) of the film are stabilized by the repulsive hydration interaction. Parameters drawn from force measurements between interacting lipid bilayers are used to obtain values of marginal and dominant wavelengths. The theoretical predictions are discussed within the framework of vesicle–vesicle interaction and fusion.