Alignment visualization using electroconvection of planar nematics

In electroconvection experiments with planarly aligned nematic liquid cryst als 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 direct or orientation. We report atomic force microscopy and x-ray measurements th at 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 an d after filling the system using the electroconvection pattern. This is a c onvenient tool for exploring new director configurations. We confirm for th e observed surface structure that when flow and surface designate different orientations, the mechanical surface treatment dominates. We have been abl e to obtain regions with radial director orientation of millimeter size. Su ch an alignment renders possible new types of electroconvection experiments . (C) 2000 American Institute of Physics. [S0034-6748(00)01007-8].