LAUSR

We present an unusual temperature dependence of polar anchoring torque in a nematic liquid crystal contacting with a perfluoropolymer surface. Whereas the anchoring torque is conventionally expected to increase with decreasing temperature, we show that the polar anchoring torque in the present system decreases with decreasing temperature. This causes an orientational transition from planar to vertical during cooling. We explain the origin of this phenomenon as the result of thermodynamic growth and spreading of surface-localized smectic wetting sheets. We clearly show that the coverage of these wetting sheets on the surface creates a vertical state that violates the initial planar anchoring in the bulk, thereby reducing the effective polar anchoring torque.