DIVERGENCE OF THE POINT TENSION AT WETTING

The line tension, tau (free energy associated with the line of contact ) is expected to have interesting singular behaviour at the wetting tr ansition, as has already been inferred from mean field theory and scal ing arguments. In order to investigate this behaviour, we consider an exactly soluble two-dimensional Ising model with appropriate wetting b oundary conditions and investigate suitable definitions of tau, now a point tension, associated with the junction of an interface tilted wit h average angle theta(c) and another lying along the substrate. Size-d ependent fluctuations in the point of contact indicate that tau be def ined through a convolution sum. Hence tau almost-equal-to ln (1/theta( c)) as theta(c) down 0 (wetting transition), which can be understood a s a consequence of the entropic repulsion of the tilted part of the in terface against the substrate, This logarithmic divergence is consiste nt with the recent scaling hypothesis of Indekeu and Robledo.