Defects, Surface Anchoring, and Three-Dimensional Director Fields in the Lamellar Structure of Cholesteric Liquid Crystals as Studied by Fluorescence Confocal Polarizing Microscopy

Abstract

We study three-dimensional director patterns and defects in cholesteric liquid crystals using fluorescence confocal polarizing microscopy for nondestructive three-dimensional imaging. We establish the detailed director fields of dislocations, their kinks, as well as the disclination nodes and oily streaks. Weak surface anchoring of the director at the bounding plates causes attraction, while strong anchoring causes repulsion between the edge dislocation and a boundary. We use a coarse-grained models of cholesteric elasticity and surface anchoring potential to explain the experimental results. We study dynamics of defects, and glide and climb of dislocations. We also consider the Peierls-Nabarro mechanisms hindering glide of dislocations across the cholesteric layers. The static and dynamic properties of defects in cholesteric lamellae can be used as a model for understanding similar phenomena in other lamellar systems, such as diblock copolymers and SmA liquid crystals.