A liquid crystal
is a molecular crystal with properties that are both solid- and liquid-like. Liquid
crystals are composed predominantly of rod-like or disc-like molecules, that can exhibit
one or more different, ordered fluid phases as well as the isotropic
fluid; the translational order is wholly or partially destroyed but a considerable
degree of orientational order is retained on passing from the crystalline to the liquid
phase in a mesomorphic transition
- Transition to a nematic phase.
A mesomorphic transition that occurs when a molecular crystal is heated to form a nematic phase in which the
mean direction of the molecules is parallel or antiparallel to an axis known as the
- Transition to a cholesteric phase.
A mesomorphic transition that occurs when a molecular crystal is heated to form a cholesteric phase in which
there is simply a spiralling of the local orientational order perpendicular to the
long axes of the molecules.
- Transition to a smectic state.
A mesomorphic transition that occurs when a molecular crystal is heated to yield a smectic state in which there is a one-dimensional density wave which produces very soft/disordered
PAC, 1994, 66, 577
(Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations
on page 584
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook