Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 5M

Year: May 2013

The three different phases of Liquid Crystals include

• Nematic Phase
• Smectic Phase
• Cholestric Phase

Nematic Phase	Smectic Phase	Cholestric Phase
Characterized by molecules that have no positional order but tend to point in the same direction (along the director).	Molecules in this phase show a degree of translational order.	Composed of molecules containing a chiral center which produces intermolecular forces that favour alignment between molecules at a slight angle to one another.
It has a thread like topological defect and the molecules maintain the general orientational order.	In the smectic state, the molecules maintain the general orientational order of nematics, but also tend to align themselves in layers or planes.	The structure can be visualized as a stack of very thin 2-D nematic-like layers with the director in each layer twisted with respect to those above and below forming a continuous helical pattern about the layer normal

Nematics have fluidity similar to that of ordinary (isotropic) liquids but they can be easily aligned by an external magnetic or electric field. Aligned nematics have the optical properties of uniaxial crystals and this makes them extremely useful in Liquid Crystal Display (LCD).