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mohammad.kool@hotmail.com
01/15/16
 1888-1899
◦ 1888, Austrian Botanist
Freidrich Reinitzer
discovers liquid
crystals.
01/15/16
Milky liquid at 145oC
Clear ...
01/15/16
Solid
Liquid crystal
“fourth state of matter”
Liquid
Gas
01/15/16
Liquid Crystal – a stable phase of matter
characterized by anisotropic properties
without the existence of a 3-di...
01/15/16
vs.
Anisotropic
Liquids and gases
(uniform properties in all
directions).
Liquid Crystals
have orientational order
 A fluid phase in which a liquid crystal flows and will take the shape of
its container. It differs from liquid that ther...
 A phase that exists between solid and liquid
 Discovered in 19th century when studying a cholesterol
derivative
 Assuming that the direction
of preferred orientation in a
liquid crystal (LC) is ↑, this
direction can be
represented by...
Typical Representation of a LC Molecule
Mesogens
Note: these molecules possess
very strong dipole moment
The liquid crystal molecules prefer to align parallel to
each other because of the strong intermolecular
attraction (π-π i...
01/15/16
Nematic, Smectic & Cholesteric
Anisotropic substances may go through one or several
Liquid Crystal Phases
 Molecules in this
phase are long and
rod-like in shape.
They are free to
move in space.
 This phase can be
reached at lower
temperatures than the
nematic phase.
 Molecules align
themselves in layers.
(They ar...
 Molecules with intermolecular forces that favor alignment
between molecules at a slight angle to one another
 The direc...
 If an electric field is
applied to a liquid
crystal the
molecules will align
in the same
direction as the
field.
Criteria for a Molecule being
Liquid Crystalline
• The molecule must be elongated in shape-
length should be significantly...
A side chain R, two or more
aromatic rings A and A’, connected
by linkage groups X and Y, and at
the other end connected t...
01/15/16
N-(4- Methoxybenzylidene)-4-butylaniline (MBBA)
molecule
01/15/16
 Temperature sensors
 Medical use
 Electrical devices
 Solar cells
 Chromatographic separations
 Displays
 Liquid C...
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Liquid crystals

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Liquid crystals

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Liquid crystals

  1. 1. mohammad.kool@hotmail.com 01/15/16
  2. 2.  1888-1899 ◦ 1888, Austrian Botanist Freidrich Reinitzer discovers liquid crystals. 01/15/16 Milky liquid at 145oC Clear liquid at 179 ° C
  3. 3. 01/15/16 Solid Liquid crystal “fourth state of matter” Liquid Gas
  4. 4. 01/15/16 Liquid Crystal – a stable phase of matter characterized by anisotropic properties without the existence of a 3-dimensional crystal lattice – generally lying between the solid and isotropic (“liquid”) phase.
  5. 5. 01/15/16 vs. Anisotropic Liquids and gases (uniform properties in all directions). Liquid Crystals have orientational order
  6. 6.  A fluid phase in which a liquid crystal flows and will take the shape of its container. It differs from liquid that there are still some orientation order possessed by the molecules
  7. 7.  A phase that exists between solid and liquid  Discovered in 19th century when studying a cholesterol derivative
  8. 8.  Assuming that the direction of preferred orientation in a liquid crystal (LC) is ↑, this direction can be represented by an arrow, called the director of the LC.  Each molecule is orientated at some angle to the director.
  9. 9. Typical Representation of a LC Molecule Mesogens Note: these molecules possess very strong dipole moment
  10. 10. The liquid crystal molecules prefer to align parallel to each other because of the strong intermolecular attraction (π-π interaction)
  11. 11. 01/15/16 Nematic, Smectic & Cholesteric Anisotropic substances may go through one or several Liquid Crystal Phases
  12. 12.  Molecules in this phase are long and rod-like in shape. They are free to move in space.
  13. 13.  This phase can be reached at lower temperatures than the nematic phase.  Molecules align themselves in layers. (They are restricted to their plane.)  More order and higher viscosity
  14. 14.  Molecules with intermolecular forces that favor alignment between molecules at a slight angle to one another  The director is not fixed in space as in a nematic phase, it rotates throughout the sample
  15. 15.  If an electric field is applied to a liquid crystal the molecules will align in the same direction as the field.
  16. 16. Criteria for a Molecule being Liquid Crystalline • The molecule must be elongated in shape- length should be significantly greater than its width • Molecule must have some rigidity in its central region • The ends of the molecule are somewhat flexible
  17. 17. A side chain R, two or more aromatic rings A and A’, connected by linkage groups X and Y, and at the other end connected to a terminal group R’. 01/15/16
  18. 18. 01/15/16 N-(4- Methoxybenzylidene)-4-butylaniline (MBBA) molecule
  19. 19. 01/15/16
  20. 20.  Temperature sensors  Medical use  Electrical devices  Solar cells  Chromatographic separations  Displays  Liquid Crystal Thermometers  Optical Imaging

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