ABSTRACT
The order in a crystal is usually both positional and orientational, in that the molecules are constrained both to occupy specific sites in a lattice and to point their molecular axes in specific directions. The molecules in all liquid crystal phases diffuse about much like the molecules of a liquid, but as they do so they maintain some degree of orientational order and sometimes some positional order also. In contrast to liquid crystals that always possess orientational order and sometimes have positional order, there is another phase of matter that possesses positional order but no orientational order. Liquid crystals are currently an important phase of matter both scientifically and technologically. The most common type of molecule that forms liquid crystal phases is a rodshaped molecule. The core of a typical discotic liquid crystal molecule is usually based on benzene, triphenylene, or truxene, with six or eight side chains, each resembling a typical calamitic liquid crystal molecule.
