Liquid Crystals

Definition

Liquid Crystal is a substance which flows like a liquid but has some degree of ordering in the arrangement of its molecules.

•  In crystalline state, not only do the molecules occupy specific positions but also tend to orient in a preferred direction. Thus the molecules have both positional and orientational order.

• In liquid state, the molecules neither occupy specific positions nor are oriented in any particular manner. The molecules are free to move at random and collide with one another abruptly changing their positions thus losing both positional and orientational order.

• Intermediate between the solid and the liquid state exists the liquid crystal phase, wherein the molecules are free to move but are oriented in a particular manner. The molecules have no positional order but retain some orientation order.
•  Liquid crystal phase is also called mesophase and the molecules, which can exist in
  mesophase, are called mesogens.
• Director : in liquid crystal state the molecules have no positional order but are oriented
  in a particular direction. The preferred orientation of the molecules of a liquid crystal is
  called the Director.