Steady motion of the three phase contact line in model Langmuir-Blodgett systems

Abstract

The forced steady motion of the three phase contact line in model Langmuir-Blodgett systems is studied. Different “Y”-multilayers served to vary the dynamic behaviour of the contact perimeter at constant viscosity, density and surface tension of the subsolution. The specific velocity dependences of the receding contact angleϕ r and dynamic capillary heightL c stress the significance of the three phase contact line properties in the kinetics of wetting in the whole steady velocity range. The presentation of the experimental results in the Blake and Haynes theoretical scale confirms this conclusion. The deviation from the theoretical trend observed with arachidic acid system at high velocities is related to the bulk drag force which becomes significant under these conditions. A model considering the drag force location in a receding meniscus at high withdrawal velocities is proposed, in which the Blake/Haynes relation is taken as a boundary condition of the bulk hydrodynamic problem. The latter is assumed to be similar to the problem of film entrainment by a moving solid wall. The experimental data show good agreement with the equation obtained on the basis of the proposed model.