Columnar phase 1104514 186092083 2008-01-22T11:21:13Z SmackBot 433328 Date/fix the maintenance tags or gen fixes using [[Project:AutoWikiBrowser|AWB]] {{Unreferenced|date=January 2008}} The '''columnar phase''' is a class of [[liquid crystal|liquid-crystalline phases]] in which molecules assemble into cylindrical structures to act as [[mesogen]]s. Originally, these kinds of liquid crystals were called discotic liquid crystals because the columnar structures are composed of flat-shaped discotic molecules stacked one-dimensionally. Since recent findings provide a number of columnar liquid crystals consisting of non-discoid mesogens, it is more common now to classify this state of matter and compounds with these properties as columnar liquid crystals. ===Classes of Columnar Phases=== Columnar liquid crystals are grouped by their structural order and the ways of packing of the columns. [[Nematic]] columnar liquid crystals have no long-range order and are less organized than other columnar liquid crystals. Other columnar phases with long-range order are classified by their two-dimensional lattices: hexagonal, tetragonal, rectangular, and oblique phases. The discotic nematic phase includes nematic liquid crystals composed of flat-shaped discotic molecules without long-range order. In this phase, molecules do not form specific columnar assemblies but only float with their short axes in parallel to the director (a unit vector which defines the liquid-crystalline alignment and order). ===Current Topics of Interest=== The first discotic liquid crystal was found in [[1977]] by the Indian researcher Sivaramakrishna Chandrasekhar. This molecule has one central [[benzene]] ring surrounded by six [[alkane|alkyl]] chains. Since then, a large number of discoid [[mesogen|mesogenic]] compounds have been discovered in which [[triphenylene]], [[porphyrin]], [[phthalocyanine]], [[coronene]], and other [[aromatic]] molecules are involved. The typical columnar liquid-crystalline molecules have a pi-electron-rich aromatic core attached by flexible alkyl chains. This structure is attracting particular attention for potential molecular electronics in which aromatic parts transport electrons or holes and alkyl chains act as insulating parts. The advantages of liquid-crystalline conductors are their anisotropy, processibility, and self-healing characteristics for structural defects. [[Category:Liquid crystals]]