Liquid crystals are a state of matter with properties between liquids and solids, first examined by Friedrich Reinitzer in 1888. They are classified into thermotropic and lyotropic types, with phases including nematic and smectic, and can be influenced by temperature, pressure, and electric fields. The nematic phase is predominantly used in LCD technology and other applications such as thermometers and protective gear.

1. Liquid crystals (LCs)
are a state of matter that
have properties
between those of a
conventional liquid and
those of a solid crystal.

2. Yerra Bharath
G V S R Pavan Kumar

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.

5. C
molecule
Chemical structure of Cholesteryl benzoate molecule

6. vs.vs.
AnisotropicAnisotropic
Liquids and gases
(uniform properties in all
directions).
Liquid Crystals
have orientational order

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

10. Classification
Based on breaking order of the solid
state
1. Thermotropic liquid
crystals
2. Lyotropic liquid crystals

11. Thermotropic phases are
those that occur in a certain
temperature range.
Types
1. Nematic
2. Cholesteric (Chiral
Nematic)
3. Smectic

12. There are 2 basic phases
Nematic & Smectic
Anisotropic substances
may go through one or several
Liquid Crystal Phases

13. Nematic phase

14. Smectic phases

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)

23. Computer Monitor
Light Shutters
Small Displays

25. LiquidCrystal Displays (LCDs)
Liquid crystal thermometers Helmetsand Bullet-proof vests:
Battery testing strips (used by DuraCell)