Surfaces and Interfaces of Free-Standing Smectic Films

Abstract

Free-standing smectic films are unique fluid objects with an exceptionally large surface-to-volume ratio. They are excellently suited for studies of surface and interface properties of liquids. We describe surface tension measurements in the smectic and isotropic phases, with particular emphasis on anomalies near the phase transitions. A model that considers the excess surface entropy of ordered surface layers is applied to describe the experimental observations qualitatively and quantitatively. From the geometrical properties of isotropic droplets in free-standing films and from the forces acting on these droplets, interface tensions between the smectic and isotropic phases are derived. Finally, we report measurements of the gas permeation through smectic films and develop a model for the description of the film-thickness dependence of the permeation coefficient.