Structures: Liquid crystals

Liquid crystal systems continue to reveal new and unique manifestations of varying symmetry, dimensionality, and order in different phases. These phases serve as testing grounds for scientific concepts and predictions from theoretical considerations. This article provides an overview of the liquid crystal phases and phase transitions that have engendered significant scientific interest and investigations over the past two decades. In addition to the conventional nematic phase, general descriptions of the twist-bend, ferroelectric nematic, biaxial nematic, and blue phases are presented. Calamitic phases formed by mesogens having a molecular dipole and a chiral center, mesophases (B1-B7) arising from a bent shape of the molecular core, and discotic phases of oblate-core molecules are described.