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

The polar anchoring strength coefficient W and polar pretilt angle θ₀ 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∝θ₀² over the range 0^∘≤θ₀35^∘. The results provide a confirmation of the dual easy axis model, wherein the liquid crystal director adopts an equilibrium orientation θ₀ at the substrate that is determined by competition between a pair of preferred orientation directions.