C. Papenfuss and W. Muschik
Theory of two-dimensional liquid crystals - Influence of curvature, liquid-crystalline ordering and electromagnetic fields
Thin Solid Films 284-285, 1996, 484-488

The balance equations for surface densities in two-dimensional liquid crystals are presented. In order to obtain a closed system of differential equations out of them, constitutive equations are needed. These constitutive equations are restricted by the second law of thermodynamics. From these restrictions the surface stress tensor is calculated. It is shown that the normal stresses do not vanish. They have an influence in capillary rise experiments for measuring the surface tension.