The document discusses liquid crystals, their definition, types, properties and applications. It defines liquid crystals as matter in a state between liquid and solid crystal, possessing properties of both. Liquid crystals are divided into thermotropic, lyotropic and metallotropic types based on the factors inducing their phase transitions. Their properties include orientational order, birefringence, and response to external fields. Common applications mentioned are LCD displays, dyes, advanced materials and drug delivery. Liquid crystal technology finds use in telecommunication switches for routing wavelength division multiplexed optical signals.

1. LIQUID CRYSTAL
AND IT’S APPLICATION

2. ROLL NO. NAME OF STUDENT
1413037 KSHITIJ PATIL
1413040 VAIBHAV RAO
1413052 RINKOO SINGH
1413057 TANVI VISHWASRAW
1413058 SOURABH WALVEKAR
1413055 SIDDESH VILAS PAWAR

3. ROLL NO NAME OF STUDENT
1413033 TEJUL PANDIT
1413034 SHUBHAM PAREEK
1413035 VISHAL PATANGRAO
1413036 RAHUL PATEL
ROLL NO. NAME OF STUDENT
1413037 KSHITIJ PATIL
1413038 TRISHALA P PAWAR
1413039 VIPUL RAJDERKAR
1413040 VAIBHAV RAO
ROLL NO. NAME OF STUDENT
1413041 BHUSHAN SABADRA
1413042 MEHUL SANYASHIV

4. ROLL NO: NAME OF STUDENT
1413043 SIDDHESH SAWANT
1413044 CHIRAG SHAH
1413045 JANAVI SHAH
1413046 NIRAV SHAH
1413047 KUNJ SHAH
1413048 YASH SHAH
1413049 MOHAMED SHAYERWALA
ROLL NO: NAME OF STUDENT
1413050 RUTVI SHETH
1413051 ROHIT SHIVTHARE
1413052 RINKOO SINGH
1413053 AKASH SUMARIA
1413054 MONISH THAKKAR
1413055 SIDDESH PAWAR
1413056 KRUNAL VANI
1413057 TANVI VISHWASRAW
1413058 SOURABH WALVEKAR
1413059 VAIBHAV YADAV
1413060 CHIRAG THAKKAR
1413061 RAKSHIT RATHOD
1413062 SAPNA THAKKAR
1413063 MANSI SHAH

5. DEFINITION
Liquid crystals (LCs) are matter in a state that has
properties between those of conventional liquid and
those of solid crystal.
For instance, a liquid crystal may flow like a
liquid, but its molecules may be oriented in a
crystal-like way

6. Also defined on..
There are many different types of liquid-crystal
phases, which can be distinguished by their
different optical properties (such as
birefringence).

7. LIQUID CRYSTAL..
A state that occurs between a solid & a liquid
Possess properties characteristics of both
liquids & crystalline solids
Also possess properties not found in either
liquids or solids
May response to external perturbations & some
changes colour with temperature

8. HISTORY
• In 1888, Austrian botanical physiologist Friedrich
Reinitzer, working at the Karl-Ferdinands-
Universitat, examined the physico-chemical properties
of various derivatives of cholesterol which now
belong to the class of materials known as cholesteric
liquid crystals.
• At 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. The phenomenon is
reversible.

9. HISTORY
Reinitzer had discovered and
described three important features
of cholesteric liquid crystals

10. 1.THERMOTROPIC PHASE
2.LYOTROPIC PHASE
3.METALLOTROPIC PHASE
THEY CAN BE DIVIDED INTO:

11. Thermotropic liquid crystals are divided as:
(Phase transition depends on temperature)
Nematic
Smectic
Cholesteric/ Chiral
Blue
Discotic
THERMOTROPIC

12. AS TEMPERATURE INCREASES...
▪ The first liquid crystal phase is the smectic A , where
there is layer-like arrangement as well as translational
and rotational motion of the molecules.
▪ A further increase in temperature leads to the nematic
phase, where the molecules rapidly diffuse out of the
initial lattice structure and from the layer-like
arrangement as well.
▪ At the highest temperatures, the material becomes an
isotropic liquid where the motion of the molecules
changes yet again

13. 1: NEMATIC
▪ Simplest form is a nematic liquid crystal
i.e. long-range orientational order but no
positional order
▪ The preferred direction is known as director

14. NEMATIC
• Despite the high degree of orientational order,
nematic phase as a whole is in disorder i.e. NO
MACROSCOPIC ORDER (orientation within a group is
similar but not from one group to another)
• Structure of nematic phase can be altered in a
number of ways. E.g. electric or magnetic field or
treatment of surfaces of the sample container
• Thus, possible to have microscopic order &
macroscopic order

15. 2: SMECTIC PHASES
• The smectic phases, which are found at lower
temperatures than the nematic, form well-defined layers
that can slide over one another in a manner similar to
that of soap.
• The word "smectic" originates from the Latin word
"smecticus", meaning cleaning, or having soap like
properties.
• The smectics are thus positionally ordered along one
direction.
• In the Smectic A phase, the molecules are oriented
along the layer normal, while in the Smectic C phase
they are tilted away from the layer normal.

16. SMECTIC PHASES
• SMECTIC phase occurs at temperature below nematic or
cholesteric
• Molecules align themselves approx. parallel & tend to
arrange in layers
• Not all positional order is destroyed when a crystal
melts to form a smectic liquid crystal
• Chiral smectic C liquid crystals are useful in LCDS

17. 3:CHIRAL PHASES
▪ THE CHIRAL NEMATIC PHASE EXHIBITS CHIRALITY
(HANDEDNESS). THIS PHASE IS OFTEN CALLED THE
CHOLESTERIC PHASE BECAUSE IT WAS FIRST OBSERVED FOR
CHOLESTEROL DERIVATIVES
▪ ONLY CHIRAL MOLECULES (I.E., THOSE THAT HAVE NO
INTERNAL PLANES OF SYMMETRY) CAN GIVE RISE TO SUCH
A PHASE. THIS PHASE EXHIBITS A TWISTING OF THE
MOLECULES PERPENDICULAR TO THE DIRECTOR, WITH THE
MOLECULAR AXIS PARALLEL TO THE DIRECTOR.

18. CHIRAL PHASES
- In cholesteric phase, there is orientational order
& no positional order, but, director is in helical
order.
▪ The structure of cholesteric depends on the pitch,
the distance over which the director makes one
complete turn
– one pitch - several hundred nanometers
▪ Pitch is affected by:-
– temperature
– pressure
– electric & magnetic fields

19. 4:BLUE PHASES
▪ Blue phases are liquid crystal phases that appear
in the temperature range between a chiral nematic
phase and an isotropic liquid phase.
▪ Blue phases have a regular three-dimensional cubic
structure of defects with lattice periods of
several hundred nanometers, and thus they exhibit
selective Bragg reflections in the wavelength range
of visible light corresponding to the cubic
lattice.

20. 4:BLUE PHASES
• Although blue phases are of interest for fast light
modulators or tunable photonic crystals, they exist in
a very narrow temperature range, usually less than a
few kelvin.
• Recently the stabilization of blue phases over a
temperature range of more than 60 K including room
temperature (260–326 K) has been demonstrated
• Blue phases stabilized at room temperature allow
electro-optical switching with response times of the
order of 10−4 s.

21. liquid crystals are divided as:
2.LYOTROPIC LIQUID CRYSTAL

22. LYOTROPIC LIQUID CRYSTAL
• A lyotropic liquid crystal consists of two or more
components that exhibit liquid-crystalline properties
in certain concentration ranges.
• In the lyotropic phases, solvent molecules fill the
space around the compounds to provide fluidity to the
system.
• In contrast to thermotropic liquid crystals, these
lyotropics have another degree of freedom of
concentration that enables them to induce a variety of
different phases.

23. LYOTROPIC LIQUID CRYSTAL
• A compound that has two immiscible hydrophilic and
hydrophobic parts within the same molecule is called an
amphiphilic molecule.
• Many amphiphilic molecules show lyotropic liquid-
crystalline phase sequences depending on the volume
balances between the hydrophilic part and hydrophobic
part.
• These structures are formed through the micro-phase
segregation of two incompatible components on a nanometer
scale.
• Soap is an everyday example of a lyotropic liquid
crystal.

24. LYOTROPIC LIQUID CRYSTAL
• A liquid crystalline material is called lyotropic if
phases having long-ranged orientational order are induced
by the addition of a solvent.
• Historically the term was used to describe materials
composed of amphiphilic molecules.
• Such molecules comprise a water-loving 'hydrophilic'
head-group (which may be ionic or non-ionic) attached to
a water-hating 'hydrophobic' group.

25. LYOTROPIC LIQUID CRYSTAL
• In principle, increasing the amphiphile concentration
beyond the point where lamellar phases are formed would
lead to the formation of the inverse topology lyotropic
phases, namely the inverse cubic phases, the inverse
hexagonal phase (HII) and the inverse micellar cubic
phase.
• In practice inverse topology phases are more readily
formed by amphiphiles that have at least two hyrocarbon
chains attached to a headgroup.
• The most abundant phospholipids that are found in cell
membranes of mammalian cells are examples of amphiphiles
that readily form inverse topology lyotropic phases.

26. liquid crystals are divided as:
3.METALLOTROPIC LIQUID CRYSTAL

27. METALLOTROPIC LIQUID CRYSTAL
• Liquid crystal phases can also be based on low-melting
inorganic phases like ZnCl2 that have a structure formed
of linked tetrahedra and easily form glasses.
• The addition of long chain soap-like molecules leads to a
series of new phases that show a variety of liquid
crystalline behavior both as a function of the inorganic-
organic composition ratio and of temperature. This class
of materials has been named metallotropic.

28. METALLOTROPIC LIQUID CRYSTAL
Liquid crystals consist of anisotropic molecular units,
and most are organic molecules.
Materials incorporating metals into anisotropic molecules,
described as metallomesogens, have been prepared.
Achieving liquid-crystalline behaviour in inorganic fluids
should be possible if the anisotropic structure can be
retained or designed into the molten phase.

29. PROPERTIES OF LIQUID CRYSTAL
▪ Liquid crystal can flow like a liquid, due to
loss of positional order
▪ Liquid crystal is optically birefringent, due to
its orientation order
▪ Transition from crystalline solids to liquid
crystals caused by a change of temperature –
gives rise to thermotropic liquid crystals
– substances that are most likely to form a liquid
crystal phase at a certain temperature are
molecules that are elongated & have some degree
of rigidity.

30. PROPERTIES OF LIQUID CRYSTAL
▪ Liquid crystal phases are generally
cloudy in appearance, which means that
they scatter light in much the same
way as colloids such as milk.
▪ This light scattering is a
consequence of fluctuating regions of
non-uniformity as small groups of
molecules form and disperse.

31. PROPERTIES OF LIQUID CRYSTAL
• The anisotropy of liquid crystals causes them to
exhibit birefringence. That is, light that enters
the crystal is broken up into two oppositely-polarized
rays that travel at different velocities.
• Observation of a birefringent materal between crossed
polarizing filters reveals striking patterns
and color effects.

32. PROPERTIES OF LIQUID CRYSTAL
Liquid crystals, like all other kinds of matter, are subject to
thermal expansion. expansion.
As the temperature rises, the average spacing between
the aligned molecules of a nematic phase increases, thus causing
the e-ray to be increasingly retarded with respect to the o-ray.
Inexpensive thermometers can be made by printing a succession of
suitably formulated LC mixtures on a paper or plastic strip
which is held in contact with the surface whose temperature is
to be

33. TYPICAL CHEMICAL STRUCTURES
▪ cholesterol ester
▪ phenyl benzoates
▪ surfactants such as polyethylene-oxides,
alkali soaps, ammonium salts, lecithin
▪ paraffin's
▪ glycolipids
▪ cellulose derivatives

34. OPTICAL RESPONSE
•Applied voltage changes tilt angle
of nematic layers
•Tilt Angle changes light
transmission

35. •Abrupt tilt angle change with 270o
twist
•On/Off response faster
•210o used for grayscale

36. •Nematic exists over larger
range than either separate
solution does
Temperature Range

37. ORDER PARAMETER
The description of liquid crystals involves an
analysis of order.
A second rank symmetric traceless tensor order
parameter is used to describe the orientational
order of a nematic liquid crystal, although a
scalar order parameter is usually sufficient to
describe uniaxial nematic liquid crystals.

38. TYPICAL CHEMICAL STRUCTURES
▪ cholesterol ester
▪ phenyl benzoates
▪ surfactants such as polyethylene-oxides,
alkali soaps, ammonium salts, lecithin
▪ paraffin's
▪ glycolipids
▪ cellulose derivatives

39. TYPICAL APPLICATIONS...
Many more....
MAKING IT HAPPEN
• LCD displays
• dyes (cholesterics)
• advanced materials (Kevlar)
• membranes
• temperature measurement (by
changing colors)
• solvents for GC, NMR,
reactions, etc.
• Drug delivery

40. LCD LAYERS...
• A liquid-crystal
display (LCD) is
a flat panel
display,
electronic visual
display, or video
display that uses
the light
modulating
properties of
liquid crystals.
• Liquid crystals
do not emit light
directly.

41. TWISTED NEMATIC LCD...
A super-twisted
nematic display
(STN) is a type
of monochrome
passive-matrix
liquid crystal
display (LCD).

42. Application of Liquid Crystal Technology to
Telecommunication Devices
A dense wavelength division
multiplexed (DWDM) optical network,
as with any information network,
requires switches to perform routing of
the signals. DWDM networks pass
several information channels along the
same optical waveguide (optical fiber):
each channel corresponds to a different
wavelength of light with the
wavelengths typically separated by less
than a nanometer. Consequently
DWDM networks require switches that
are wavelength selective with very high
resolution

43. © 2014 E.X.T.C SOMAIYA COLLEGE OF ENGINEERING