Polar Anchoring Strength of a Tilted Nematic: Confirmation of the Dual Easy Axis Model

The polar anchoring strength coefficient $W$ and polar pretilt angle ${\theta }_0$ were measured simultaneously for the liquid crystal pentylcyanobiphenyl at a rubbed polyimide alignment layer that is ordinarily used for vertical alignment. It was found that $W\propto {\theta }_0^2$ over the range $0°\le {\theta }_0\lesssim 35°$. The results provide a confirmation of the dual easy axis model, wherein the liquid crystal director adopts an equilibrium orientation ${\theta }_0$ at the substrate that is determined by competition between a pair of preferred orientation directions. DOI: http://dx.doi.org/10.1103/PhysRevLett.94.057802 © 2005 The American Physical Society