About Liquid Crystals
The Liquid-crystalline State - Molecular Shape and Structure and Liquid Crystals - Thermotropic Liquid Crystals - Lyotropic Liquid Crystals - Plastic Crystals - Structures of Thermotropic Liquid Crystals - Structures of Smectic Liquid Crystals
The Liquid-crystalline State
A liquid-crystalline mesophase is a state of matter which exists between the organized solid and the amorphous liquid. Strictly, the liquid crystal or mesomorphic state is made up of a number of orientationally ordered mesophases which occur between the breakdown of translational positional ordering of the molecules in a crystal and the formation of the orientationally disordered state of a liquid.
Typically the breakdown in molecular ordering on passing from a crystal to a liquid can be achieved either by changing the temperature of the material or by dissolving the material in a liquid. Liquid crystals that are formed on heating and/or cooling processes are called thermotropic liquid crystals, and those that are formed when a material dissolves in a solvent are called lyotropic liquid crystals. Typically the liquid crystal state has come to be defined as any state of matter where the molecules are orientationally ordered, but yet are in dynamic motion. Thus, this definition also includes soft crystals, sometimes called anisotropic plastic crystals, which can be formed between the solid and the liquid crystal states.
Liquid crystals stand between the
isotropic liquid phase and the
strongly organized solid state.
Life stands between complete disorder,
which is death, and complete rigidity,
which is death again.
D.G. Dervichian
Mol. Cryst. Liq. Cryst., 40, 733, (1977)
The Liquid-crystalline State - Molecular Shape and Structure and Liquid Crystals - Thermotropic Liquid Crystals - Lyotropic Liquid Crystals - Plastic Crystals - Structures of Thermotropic Liquid Crystals - Structures of Smectic Liquid Crystals