4. History
In 1888, Austrian botanical
physiologist Friedrich Reinitzer,
examined that Cholesteryl benzoate
had two distinct melting points.
145.5 °C (293.9 °F) it melts into a
cloudy liquid, and at 178.5 °C
(353.3 °F) ) it melts again and the
cloudy liquid becomes clear.
7. Liquid crystals are highly
anisotropic fluids that exists
between the solid and
liquid phases.
This dual physical
properties is referred to as
mesomorpism.
8. Characteristics of liquid crystals
1. Positional order
2. Orientational order
3. Bond orientational order
9. The orientation of Liquid Crystals can be affected
by…
Pressure
Temperature
Electrical Field
S. Palmer, LCTec Displays, Inc. 2005
15. The chiral nematic phase) (left, also called the
Cholesteric phase, and the smectic C* phase (right).
16. The molecules in nematic
structure maintain a parallel or
nearly parallel arrangement to
each other along the molecular
axes. They move in three
directions and can rotate about
one axis hence the structure is
one dimensional.
17. Cholesteric (Chiral Nematic)
It is modification of nematic
liquid crystal because many
compounds of this are
derivatives of cholesterol
18. p refers to the
chiral pitch, is
the distance it
takes for the
director to rotate
one full turn in
the helix.
19. Smectic
The molecules in this phase show
a degree of translational order
which was not present in the
nematic.
Nearly 8 to 9 smetic phases are
labeled by alphabets.
20. Lyotropic liquid crystals
Structure of lyotropic liquid crystal
The red heads of surfactant molecules are in contact with
waterwhereas the tails are immersed in oil (blue): bilayer
(left) and micelle (right)
21. A lyotropic liquid crystal exhibit liquid-
crystalline properties in certain
concentration ranges.
Many amphiphilic molecules show
lyotropic liquid-crystalline phase
Examples:
1. Sodium laurate in water
2. Dhosphatidly Choline in water.
22. The Nematic phase is most commonlyThe Nematic phase is most commonly
used in Liquid Crystal Displaysused in Liquid Crystal Displays
(LCD)(LCD)