Shaping thin nematic films with competing boundary conditions.

Free interfaces of liquid crystals tend to minimise both capillarity and anchoring forces. Here we study nematic films in planar and radial geometries with antagonistic anchoring boundary conditions and one deformable interface. Assuming a perturbation ansatz we study possible couplings of the director configuration with the shape of free interfaces. In the long-wavelength limit independent of the surface tension, we find analytically the threshold thickness when the flat film becomes unstable. Next we quantify the bifurcation of a circular ring towards structures with m-fold rotational symmetry, induced by elastic anisotropy of the nematic director in the bulk. We believe that our simplified approach can give additional insight into elastic and capillary phenomena of materials with inherent liquid crystalline order and free interfaces.