Abstract

Liquid crystals are a state of matter in which the molecules diffuse randomly as in liquids but retain some orientational order as is typical of solids. Many thousands of organic compounds, including rigid-rod polymers and other macromolecules, exhibit liquid crystallinity, either in their pure form or when mixed with a liquid solvent. Liquid crystalline materials are studied both for the basic scientific understanding of this phase of matter and for the possibility of practical applications. To date, the most important application is the low power consuming liquid crystal display (LCD). Topics covered in the article include orientational and positional order in fluids, thermotropic liquid crystals, lyotropic liquid crystals, polymorphism, synthesis, polymer liquid crystals, liquid crystals in biological systems, and applications.