classification of liquid crystal ? discuss each one in detail.
Answers
Explanation:
Liquid crystals are a unique state of matter, between solid (crystalline) and liquid (isotropic) phases some compounds form a distinct, different intermediate phase, sometimes referred to as the “fourth state of matter” or “mesophase”. These compounds display properties of both solid and liquid
Liquid crystals are classified in many ways,[12][13] molecules within the mesophases (mesogens) can be calamitic (rod-like), discotic (disc-like), amphiphilic, nonamphiphilic, metal containing, non-metal containing and low molecular weight or polymeric. Liquid crystals either show thermotropic behaviour or lyotropic behaviour. Thermotropic behaviour means the compounds are liquid crystalline within a defined temperature range, below this range compounds are crystalline and above it compounds are isotropic liquids (figure 1). Thermotropic liquid crystalline compounds also require no solvent. Lyotropic liquid crystals are dependent on solvents, where solvent concentration affects aggregation and liquid crystal behaviour.
Figure 1: Rod-like (calamitic) molecules representing molecular arrangement of thermotropic liquid crystalline phase transitions.
This work is focused on calamitic, thermotropic liquid crystals. Mesophases of such liquid crystals can be divided into categories which depend on the orientation and order. The main categories are nematic (N), smectic (Sm) and cholesteric (N*) (or chiral nematic) (figure 2).
Figure 2: Molecular arrangements of different sub-phase allignments.
1.2.2 Nematic Phases
1.2.1 Smectic Phases
1.2.3 Cholesteric Phases
Figure 3: Representation of the cholesteric mesophase with the cholesteric pitch.
1.2.4 Chiral Liquid Crystals
1.3 Ionic Liquid Crystals
Liquid crystals are classified in many ways, molecules within the mesophases (mesogens) can be calamitic (rod-like), discotic (disc-like), amphiphilic, nonamphiphilic, metal containing, non-metal containing and low molecular weight or polymeric. Liquid crystals either show thermotropic behaviour or lyotropic behaviour.
All liquids show the following characteristics:
Liquids are almost incompressible. In liquids molecules are pretty close to each other. ...
Liquids have fixed volume but no fixed shape. ...
Liquids flow from higher to lower level.
Liquids have their boiling points above room temperature, under normal conditions.
Examples of Liquids
Water.
Milk.
Blood.
Urine.
Gasoline.
Mercury (an element)
Bromine (an element)
Wine.
Which type of liquid crystal is colored and changes color with temperature?
Thermochromic Liquid Crystals
Thermochromic Liquid Crystals (LCs) can be highly temperature sensitive, change to many colors, and are more expensive than leuco dyes. LCs start black below their temperature range, go through the colors of a rainbow, and back to black again above the temperature range
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