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Columnar Mesomorphic Order in Thermotropic Liquid Crystals

The first examples of thermotropic mesomorphism with discotic molecules were observed by S. Chandrasekhar in the hexa-alkanoyloxy benzenes. Since then, the columnar mesomorphic order has been deeply investigated thanks to the synthesis of many types of disk-shaped molecules. In such mesophases, the molecules are packed one upon another to form columns. These latter then organize according to a two-dimensional lattice. These last years, appeared a variety of compounds with quite different molecular architectures, exhibiting also columnar mesophases. Some significant results of the most recent systems are presented. They concern pseudo-polymeric chains of metal soaps and polycatenar molecules. These typical examples of new columnar structures are described with emphasis given on the relationships between the columnar structure and the molecular architecture, along with the specific interactions responsible for the establishment of this type of supramolecular organization.