Alignment visualization using electroconvection of planar nematics

In electroconvection experiments with planarly aligned nematic liquid crystals the director orientation is, conventionally, fixed through a mechanical treatment (rubbing) of the polymer-coated electrodes. Without rubbing, on the other hand, the flow direction during sample filling imposes the director orientation. We report atomic force microscopy and x-ray measurements that show an anisotropy in the polymer surface structure on several scales as a result of the rubbing. In particular we observe a fish-bone structure on a 10 nm scale. We visualize the orientation of the director both during and after filling the system using the electroconvection pattern. This is a convenient tool for exploring new director configurations. We confirm for the observed surface structure that when flow and surface designate different orientations, the mechanical surface treatment dominates. We have been able to obtain regions with radial director orientation of millimeter size. Such an alignment renders possible new types of electroconvection experiments.