Defects and Textures in Liquid Crystals

Defects and textures in liquid crystals are important and play crucial role in the identification of mesophase types and their properties, and in the construction and operation of display devices. Defects are local symmetry breakings in an ordered medium, while textures are an optical appearance of the specimens. They have long association with topology (arrangement of molecules). Initially this arose through Frank’s introduction of the term disinclination (now disclination) for the characteristic lines or threads. Defects appear under the polarizing microscope as ellipses, parabolas, hyperbolas, lines and points, and colorful structural singularities.  The understanding about their unique properties is essential to understand many phenomena such as phase transitions, rheology and properties, disordered systems, frustrated media, convective instabilities, shape of biological systems, etc. The present chapter 6 is devoted to the description of various aspects of defects and textures occurring in liquid crystals over the past three decades.