Optical Investigations of Twist Grain Boundary Phases Exhibiting Cylindrical and Cone-Like Domain Textures

Abstract

Polarized optical microscopy observations performed on mixtures of Liquid crystals reveal developable domain textures for Twist Grain Boundary (TGB) phases. In these structures, the smectic blocks, the grain boundaries and the layers of helical structure of TGB phase are coiled in a double-twist manner. The energy considerations require that the blocks can just be folded in cones and cylinders, the only surfaces that may be unrolled without elongations. The cones need defects to build up; in particular, a disclination is necessary all along the cone axis. In the N* phase, the field of the χ-director that emanates from the center of the spherulite has the geometry of a hedgehog point defect. The disclination lines of strength k = 2 escape into third dimension with no singularity remaining and the χ-director is not materialized. However in TGBA the χ-singularities are materialized as singularities of the slabs.

Keywords:

• CC domains
• liquid crystals
• TGB
• χ-singularities

Acknowledgments

Anjuli Khandelwal wants to thank Prof. S. D. Lee for partial support to attend ILCC08.