Chiral Symmetry Breaking in Liquid Crystals: Appearance of Ferroelectricity and Antiferroelectricity

Yoichi Takanishi

doi:10.3390/sym12111900

Abstract

The study of chiral symmetry breaking in liquid crystals and the consequent emergence of ferroelectric and antiferroelectric phases is described. Furthermore, we show that the frustration between two phases induces a variety of structural phases called subphases and that resonant X-ray scattering is a powerful tool for the structural analysis of these complicated subphases. Finally, we discuss the future prospects for clarifying the origin of such successive phase transition.

Highlights

Liquid Crystals (LCs) are stationary state meso-phases appearing between crystals and isotropic liquids, and have intermediate properties between them, i.e., fluidity and complete disorder as liquids and three-dimensional long-rage anisotropic ordering as crystals
We mainly treat the Liquid CrystalsLiquid Crystals (LCs) of rod-like molecules, in which the phase transition occurs by a thermal process
Chirality has an important factor for many scientific fields, such as biology, chemistry, and physics

Summary

Introduction

Liquid Crystals (LCs) are stationary state meso-phases appearing between crystals and isotropic liquids, and have intermediate properties between them, i.e., fluidity and complete disorder as liquids and three-dimensional long-rage anisotropic ordering as crystals. SmC* is not a real ferroelectric phase in the case of the bulk state By confining this LC into thin sandwich cells, which are composed of two clean glass plates and have a gap less than the helical pitch, and aligning the helical axis parallel to the substrate surface (called “planar alignment”) as shown, helix is suppressed (unwound) by the surface effect. In such a condition, the molecular tilting plane is parallel to the surface, so that the spontaneous polarization exists along the surface normal direction In such a thin cell whose substrate is coated with optically transparent electrodes such as ITO (Indium-Thin-Oxide), molecules are tilted in two states (A or B) by molecular tilt angle ± θ with respect to the layer normal. The indirect ferreoelectricity appears due to the surface effect, and this state is called surface-stabilized ferroelectric liquid crystals (SSFLCs) [4]

Discovery of Antiferroelectricity in Liquid Crystals

Brief Summary