Optical Activity and Ferroelectricity in Liquid Crystals

Some liquid-crystalline phases of optically active materials are themselves optically active and have dissymmetric structures. The cholesteric phase and smectics C*, I*, and F* have a helical order of their molecules. Plane-polarized light is rotated by the helix, and when the pitch of the helix is comparable to the wavelength of visible light, these phases will reflect irridescent light of a single color. The smectics phases can exhibit ferroelectricity and have been utilized recently in fast-switching light valves. A relation between the microscopic property of molecular configuration and the macroscopic properties of ferroelectricity and the rotation of plane-polarized light is developed.