Thin films in wetting and spreading

Thin films differ from bulk phases both from a thermodynamic point of view, i.e. the chemical potential of a molecule in a film depends on the film thickness, and in their dynamical response, because relaxation times may become large in these confined media. Examples of slow structural relaxation in thin films of liquid crystals, and their consequences on the wetting properties of the systems are presented first. Then, we illustrate the thermodynamic specificity of thin films when evaporation is considered. The consequences on the wetting dynamics of macroscopic evaporating droplets are presented in the last part of the paper. (C) 2002 Elsevier Science B.V. All rights reserved.