Influence of the Work of Adhesion on the Dynamic Wetting of Chemically Heterogeneous Surfaces

The velocity dependence of the dynamic contact angle for a glycerol-water mixture wetting two different chemically heterogeneous surfaces (mixed thiols on gold and partially methylated titania, 16 samples in all) was studied. The molecular kinetic theory (MKT) of wetting was used to interpret the dynamic contact angle data. The equilibrium displacement frequency (K-0) was predominantly determined by the viscous contribution from the bulk liquid, with a minor contribution from the surface. The mean distance between surface sites (lambda) decreased with increasing work of adhesion. The contact line friction coefficient zeta(0) was found to vary exponentially with the work of adhesion, enabling the unit flow volume of the liquid to be obtained.