Question

Are all liquid crystal polymers? What are thermotropic and lyotropic liquid crystals? What is the difference between nematic, smectic and cholesteric liquid crystals? Are those three the only possible liquid crystal phases?

Answer 1

***No,all liquids are not crystal polymers. Liquid crystal polymers are class of aromatic polymers.They are extremely unreactive,inert and highly resistant to fire.

***Thermotropic and lyotropic liquid crystals: In thermotropic crystals,the order of its existing components can be identified ar changed by temperature.

If the temperature is very high ,then the rise in energy and increase in motion of components will induce a phase transition and therefore the crystal will become an isotropic liquid .

On the other hand ,a liquid crystalline mesophase is called lyotropic liquid crystals .It is formed by dissolving amphiphilic mesogen in a suitable solvent under appropriate condition of concentration,temperature and pressure.Example-soap and water interaction.

****Nematic, Smectic, Cholesteric :

---- Nematic--In this the crystal molecules have no specific order, during this phase the molecules do tend to point in the same direction,which is what differntiates it from a pure liquid.

-----Smectic-- It is characterized by a slight degree of translational order in the crystal molecules which is particularly absent in nematic phase.

-----Cholesteric --- It is also known as chiral nematic liquid crystals. They basically organise in layers with no positional ordering within layers but a director axis which varies with layers. The variation of the director axis tends to be periodic in nature.

****No.

Possible liquid crystals phases:

1.Nematic

2. Smectic

3. Cholesteric

4.Discotic

5. Bowlic

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