Selective orientation of discotic films by interface nucleation

Abstract Thin films deposited from solution by the hollow capillary writing technique exhibit macroscopic uniaxial grains with an in-plane arrangement of discotic stacks. We report a method to change the orientation of thin films from in-plane to homeotropic (discotic columns perpendicular to the substrate). It is observed that annealing of open supported films at a temperature 25 °C below the equilibrium LC/isotropic phase boundary induces homeotropic alignment, while rapid cooling leads to predominantly in-plane alignment. A model based on heterogeneous nucleation at the film/substrate interface accounts for the experimental observations.