Types of liquid crystal & their properties:

Types of liquid crystals are: Smectic or soap like liquid crystals, Nematic or thread like liquid crystals and cholesteric liquid crystals.

Smectic or soap like liquid crystals:

• Crystalline state, the orientation and periodicity- all these characteristics are retained.
• On heating the crystal lose periodicity within the plane, but retain the orientation and arrangement in equispaced planes.

Nematic or thread like liquid crystals:

• These crystals on heating lose their planer or layer structure but retain a parallel alignment. Thus they retain orientation but lose periodicity.
• Hence molecules lie parallel to each other but can move up and down or sideways or can rotate along their axes.

Cholesteric liquid crystals:

• These liquid crystals have the same arrangement of molecules as in Nematic type but their optical activity is many times higher than that of its solid crystalline variety.

Discotic phase:

• They are disc shaped rather than elongated. They form thermotropic liquid crystal phases.

Properties:

• In some substance dur to its ordered arramgement the crystalline solids do not melt directly into liquid state but passes through an intermediate change that us called liquid crystal before changing to liquid state on further application of heat.
• Liquid crystal is one of the homogeneous phases with properties distinct from either traditional state. The liquid crystals show some of the properties of solid state and some of the properties of liquid state.
• The temperature at the transition point provides enough energy to disrupt the binding between some of the molecules but the energy is not sufficient to break the stong lateral force of attraction between the long molecules.
• The arrangement of molecules can be upset by very slight changes in their surrounding that is molecules in liquid crystal rearrange themselves when a small electric field is applies and the change from an isotropic to more isotropic arrangement changes the way the crystal absorbs light.
• A small electric field can disturb the alignment of molecules while the large electric field induces turbulence in thq liquid crystal with light scattering.