Characteristics of Liquid Crystal Phases

Lyotropic liquid crystal phases were discussed in detail in Section 4.10.2 and will not be considered further here. 

All thermotropic liquid crystal phases are characterized by long-range orientational order of the mesogens. However, the extent of translational order 

in a crystal there is no divergence of the amplitude of fluctuations about the average lattice positions, and there is long-range translational order. 

Because of the orientational order of the molecules, liquid crystal phases are anisotropic. This is reflected in the anisotropic response of liquid crystals to fields, specifically electric, magnetic or mechanical fields. All of these are important to the functioning of devices based on liquid crystals. 

The anisometry of mesogenic molecules leads to anisotropic polarization in electric fields. If an electric field, E, is applied to a molecule, a dipole moment is induced. The dipole tends to orient in the direction of the field. The average dipole moment per unit volume defines the polarization, P, which is proportional to the electric field  

---

Probably, the single most important characteristic of liquid-crystal phases is that as fluids they are anisotropic " this means that their physical properties are likewise anisotropic, and it is this feature which is the basis for the widespread application of the materials and also, in many cases, of their characterization. 

---