Inadequacy of Lifshitz theory for thin liquid films

Abstract

We have studied the adsorption of cyclohexane and water on molecularly smooth mica using an angle-averaging, refractive-index-matching ellipsometric technique. The isotherms are linear for submonolayer coverages, showing the importance of entropy effects, and give finite thicknesses (\ensuremath{\approxeq}2 nm) at saturation. The similarity of the two isotherms suggests that the adsorption is governed by nonspecific interactions. There is no evidence of layering but the isotherms do not agree with the Lifshitz theory of van der Waals forces.