Lyotropic

A material is called lyotropic if it forms liquid crystal phases upon the addition of a solvent. Historically the term was used to describe materials composed of amphiphilic molecules. Such molecules consist of an ionic or non-ionic hydrophilic head-group which is attracted to water, and attached to a hydrophobic group which is repelled by water. Typical hydrophobic groups are saturated or unsaturated hydrocarbon chains. Examples of amphiphilic compounds are the salts of fatty acids; phospholipids. Many simple amphiphiles are used as detergents. Lyotropic liquid crystal phases in these materials are formed by a process of self-assembly that is driven by the hydrophobic effect.