Sunday, June 20, 2010

Unit 1- Class 1- Liquid Crystals (What are liquid crystals?)

What are liquid crystals? 
There are three common states of matter, solid, liquid and gas- are different because the molecules in each state have a different degree of order.

Crystalline solids:
  1. Possess rigid arrangement of molecules
  2. Stay in a fixed position and orientation with small amount of variation from molecular vibrations
  3. There are large forces holding the molecules in place
  4. Solids are difficult to deform
Liquid phase:
  1. Molecules lack both position or orientation
  2. They are free to move in a random fashion
  3. Liquid phase has less order than the solid phase
  4. The intermolecular forces are only strong enough to keep the liquid molecules fairly close together
  5. Liquids can be easily deformed


Liquid crystals
A liquid crystal is a fluid like a liquid, but is anisotropic in its optical and electromagnetic characteristics like a solid. When the liquid crystal is formed from the isotropic state some amount of positional or orientation order is gained. It is this order that accounts for the anisotropies of the substance.

Thus liquid crystal may be described as the distinct states of matter in which the degrees of molecular ordering lie intermediate between the ordered crystalline state and the completely disordered isotropic liquid.

In a liquid crystal the molecules possess orientation order, i.e., the molecules tend remain oriented in a particular direction. The direction of preferred orientation in a liquid crystal is called the director. In a liquid crystal phase they spend more time along the director than in any other direction

No comments:

Post a Comment

Followers

Blog Archive