Chromonic review

Abstract

Chromonic systems are lyotropic liquid crystal phases formed by soluble aromatic compounds. They occur as the result of the face-to-face aggregation of the molecules into columns. There are two principal chromonic phases; the N phase which consists of a nematic array of columns and at higher concentrations, the M phase, in which the columns lie in a hexagonal array. Chromonic phases are formed by a range of multi-ring aromatic compounds including drugs, dyes and nucleic acids. They have characteristic multi-peritectic phase diagrams and distinctive optical textures.The exploitation of the unique properties of chromonic systems has scarcely started. Recent promising studies show that the combination of self-ordering, ease of alignment, sensitivity to changing conditions and additives, coupled with their optical properties and electro-optical properties, makes possible a range of sophisticated devices, including polarizers, optical compensators, light-harvesting devices and micro-patterned materials—and the fact that they are water-based, suggests a future role in biosensors for medical diagnosis.