Imprinting substrate structures onto a nematic liquid crystal.

By means of Monte Carlo simulations in the grand canonical ensemble we study the morphology of the nematic phase of a simple model liquid crystal interacting with an alternating sequence of chemically different stripes. The stripes anchor molecules such that their orientation is either parallel or perpendicular with the substrate plane. The different molecular orientations are realized through anchoring functions that cause an energetic penalty for molecules oriented in an undesired fashion. We consider combinations of monostable and degenerate anchoring fields. The nature of the nematic phase is characterized through both the local nematic order parameter and the associated local director field. We observe states of uniaxial or biaxial symmetry depending on the ratio of stripe widths and the range of fluid-substrate attraction. In some cases the specific substrate pattern causes regions of biaxial symmetry to coexist with a bulk-like regime sufficiently far away from the substrates in which the local director field indicates a (homogeneous) bent state of the nematic liquid crystal.