Lyotropic


Lyotropic

A material is called lyotropic if it forms liquid crystal phases because of the addition of a solvent. Historically the term was used to describe materials composed of amphiphilic molecules. Such molecules comprise a water-loving 'hydrophilic' head-group (which may be ionic or non-ionic) attached to a water-hating 'hydrophobic' group. 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.

The term lyotropic has also been applied to the liquid crystalline phases that are formed by certain polymeric materials, particularly those consisting of rigid rod-like macromolecules, when they are mixed with appropriate solvents. Examples are suspensions of rod-like viruses as the Tobacco Mosaic Virus as well as man-made colloidal suspensions of non-spherical colloidal particles. Other examples include DNA and Kevlar, which dissolves in sulfuric acid to give a lyotropic phase. It is noted that in these cases the solvent acts to lower the melting point of the materials thereby enabling the liquid crystalline phases to be accessible. These liquid crystalline phases are closer in architecture to thermotropic liquid crystalline phases than to the conventional lyotropic phases. In contrast to the behaviour of amphiphilic molecules, the lyotropic behaviour of the rod-like molecules does not involve self-assembly.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • lyotropic — /luy euh trop ik, troh pik/, adj. Physical Chem. noting any series of ions, salts, or radicals arranged in descending order relative to the magnitude of their effect on a given solvent. [1920 25; lyo (see LYOPHILIC) + TROPIC] * * * …   Universalium

  • lyotropic — adjective describing a liquid crystal that exhibits phase transitions as a function of concentration …   Wiktionary

  • lyotropic — SYN: lyophilic. [lyo + G. trope, a turning] * * * lyo·tro·pic .lī ə trō pik, träp ik adj of, relating to, or being a liquid crystal that is prepared by mixing two substances of which one (as water) is polar in nature and that may assume a series… …   Medical dictionary

  • lyotropic — ly·o·trop·ic …   English syllables

  • lyotropic — |līə|träpik adjective Etymology: lyo + tropic : relating to or dependent on the forces existing between components in a solution and not on their properties as individuals …   Useful english dictionary

  • lyotropic series — n HOFMEISTER SERIES * * * Hofmeister s …   Medical dictionary

  • lyotropic liquid crystals —  Lyotropic Liquid Crystals  Лиотропные жидкие кристаллы   Смесь двух или более компонентов, одним из которых является дифильная(ые) молекула(ы), а другим – вода или полярный растворитель, или их смесь. Дифильные молекулы, как правило, плохо… …   Толковый англо-русский словарь по нанотехнологии. - М.

  • Lyotropic liquid crystal — A liquid crystalline material is called lyotropic if phases having long ranged orientational order are induced by the addition of a solvent. Historically the term was used to describe materials composed of amphiphilic molecules. Such molecules… …   Wikipedia

  • lyotropic series — liotropinė eilė statusas T sritis chemija apibrėžtis Jonų eilė, sudaryta pagal jų poveikį tirpikliui. atitikmenys: angl. lyotropic series rus. лиотропный ряд …   Chemijos terminų aiškinamasis žodynas

  • lyotropic series — A listing of anions and cations in order of their effect on protein solubility (tendency to cause salting out). Essentially a competition between the protein and the ion for water molecules for hydration …   Dictionary of molecular biology