This document discusses liquid crystals, their phases and applications. It provides a history of liquid crystals, describing their discovery and classification into different phases like nematic, smectic and cholesteric based on molecular orientation. Common applications discussed include LCD displays, thermometers, imaging and protective gear. LCDs work by changing the polarization of light using liquid crystals between polarized filters. Future applications may include smart windows and 3D displays. In summary, the document covers the key topics of liquid crystal phases, LCD construction and various applications of liquid crystals.

1. Liquid crystals and their Applications
Submitted to: Dr. Shahzad A. S. Chattha
Supervisor: Madam Aqdas Noreen
Submitted by: Muhammad Minhas Azeem
Roll No.7616
Dept. of Applied Chemistry&Biochemistry
Government College University Faisalabad.

2. Contents
1. Liquid crystals
2. History
3. crystal and liquid crystal
4. Phases of liquid crystals
4.1 Nematic Phases
4.2. Smectic Phases
4.3. Cholesteric Phases
4.4. Columnar Phases
5. Construction of LCDs
6. Advantages of LCD
7. Applications
8. References

3. 1. Liquid crystals
There are different types of material in natuer.These types of mater is also called state of
matter.The nature of matreial depends upon types of attrection present between the molecules
and mobility of atom and molecules.Main state of matter is three types:
(i) solid state
(ii) liquid state
(iii) gaseous state
In solid stae , attraction between atoms and molecules is high. Molecles are close to each other
inter moleclar forces between the atom or molecules is high.So molecules of solids have fix
orientition in space which keep the molecule fix shape.So these properties soilds have high
melting and boiling point.In liquid state of matter, attractive forces between the molecules is
weak as compared to the soild but strong as compair to gass.The molecules of liquids have more
empty spaces as compair to the soild , attractive is weak the molecules move aroud with each
each other but molecules remain close to each other so fluid donot have fix shape and adapted
the shape of container that hold it.While in the cause of gass attractive forces among the
molecules is weak.The molecules are faraway from each other.The molecules have large empty
spaces so the atoms or molecules of atoms are compressable.The gass molecules have high
empaty spaces molecules of gases move randomly so the molecules of gass will expand and fill
the container.
Three states of matters have several intermediaete states , gel is a example of intermediat state.It
is like a solid and like a liquid.the liquid crystal is also anoter example of intermediate state
which have both solid and liquid phase . Liquid crystal have solid like propertis but flow like
liquid.The liquid crysatals are first observe in cholesteryl benzoate.It is first liquid crystal.
It is state between solid and liquid crystal. It have some specific properties of a liquidity,
droplets properties as well as some crystalline properties. The liquid crystals is a material that
show properties of liquid and some time soild it is substanc that like liquid and like a solid.It is
slipary in nature like a soap.This liquid crystals are find in soap dish.

4. In a liquid, all type of molecules flow around anyway . Solid, the molecules have strong
attrective forces among them.They are attrack with each so they have regular pattern and they are
arrange in specific shape.
2. History
In 1888, the Austrian chemist Friedrich Reinitzer was perform experiments to discover correct
formula and molecular weight of cholesterol. He was working on melting point. It show
veriation in melting point, He observed two melting points (178.5o
C and 145.5o
C). When the
temperature of solution reach at 145.5 o
C solution become milkey when the teperature increase
upto 178.5 o
C.The solution become transparent. He thought that changes between two teperature
is due to some impuritis but when he purify the solution he foud that this changes remain still so
he thought that obtaining of clear liquid is property of solution.
Otto Lehmann a German physicist,. He found that change the clour was new state of matter.it is
intermediate state.This new state was named "liquid crystal,"it was intermediate properties of
solid and liquid state of matter, distribute important properties of both.
In the 1960s, a French theoretical physicist, Pierre-Gilles de Gennes, He had worked on liquid
crystal and got nobel prize in Physics 1991.
3. Crystals and liquid crystal
The solid crystals and liquid crystals are different to each other due to properties.The
liquid crystals are oriented with three dimension stucture in the space.These three dimension
stucture indicate that crystals are optically active and rotate the plane polarize light.Liquid
crystals show twisted stucture while solid crystals donot show twist stucture.In liquid crystals
two different phases solid and liquid phase are mix with specific proportion but in soid
crystalphases donot have. Liquid crystals are active molecules in liquid crystals molecules of
crystala sre thin, long like a french fries. Even if the molecules' position share randomly,
their possition can be orientation with a regular pattern-then they show regular and order stucture
of liquid crystal.

5. Fig:Liquid crystals
The liquid crystal molecules do change the polarization of light. A polarizing filter works by
absorbing a particular component of the electric field. The liquid crystal molecules don't absorb
anything However, if they're arranged in the proper way, they can "twist" the light--that is,
rotate the plane in which it is polarized. if polarized light goes through the molecules, it comes
out polarized in a different direction. the light is sent through that first polarizer before it enters
the liquid crystal.
4. Liquid Crystal Phases
Ordinary liquid have same physical propeties such as electrical and megnetic properties.
Genrally in the fluid molecules in the liquid have unequal axes. This unsymetric behavior effect
rotation and orientation of light.

6. 4.1Nematic
One of the most familiar liquid phase phases is the nematic. The word nematic drived from
the Greek word, ‘nema’’ which means "thread". In nematic phase molecules havesame
direction in space but change the order.
Fig: Nematic phase
Medium size organisc molecules are use to make crystal which are enlarge as a cigar.When
temperatures is incrase , the molecules will be align immediately, as shown in the figure,at high
temperature molecules are arrenge this sequence , they are ordered oriented ,so they form
nematic liquid crystals.
The nematic phase is most important phase because they have lot off application for developing
liquid crystals.In nematic crystal phase molecules are arranged paralell to one an other other. In
this figure molecules are arrenge in rod shape linkage of crystal molecules. It have two or more
ring fixed by a central linkage group.
Typical shape of a liquid crystal molecule

7. 4.2 Smectic Phases
"Smectic" is a Greek word which means soap.This is just like a slipary soap which is present in
the lower side of soap dish. In the smectic state,the molecules are arrenge in layers or planes they
show general stuctural order in nematics.
Some compound are develop many types of smectic phase . The most common phases have
been recognize here.
 smectic-A in smectic-A there is paralell position of director and smectic plane. The
orientation of molecules is disturb in the plane.
 smectic-B in mesophase orientation of molecules are just like a smectic A ,the molecules
are arranged in layer which foem hexagonal stucture ..
 Smectic-c mesophase molecules are oriented as same order A,B but in smectic-c smetic
phase is measure by rotation of angle.
Fig: sematic phase
Director of sematic phase have chiral centar which rotate plane polarize light . chiral centar is
indicate by C*.Mesophase have different orientation and direction in the space.these layers of
mesophase is not parallel or perpendicular with each other.These one layers rotate from layer. To
next layer.the diagram of each later is shown in fig. otation of layer is represent by green
arrow.the rotation of layers form helix stucture..

8. 4.3.Cholesteric Phases:
It is type of liquid crystal .It has chiral centar and helical in stucture.This types of liquid is also
known as chiral numatic liquid crystal. They arrange in sheet with no region arrenging within
layers, but a director axis which changes with layers. The changes of the director axis regularly
in nature. This regular changes is called pitch,it is repersent as p. The pitch changes with
temperature and it is also be disturb by the boundary conditions when the chiral nematic liquid
crystal is embaded between two substrate planes..
Examples of cholesteric phases are hydroxypropyl cellulose and cholesteryl benzoate.
.
Fig. Cholesteric Phases

9. 4.4 Columnar Phases
Arrengement of crystal in column phase is structually different from above phases.The
liquid crystals are arrenge in disk shape stuctures which join to form the column so this
arrengement is complex in nature. The columns are arrenge new mesophase. The new mesophase
is two dimensional stucture
5.Construction of a liquid crystal display
LCD consist of many small rod shape molecules .These rod shape molecules are liquid
crystals.these molecules have liquid like characters.These liquid crystals have ability to curve
and rotate the light in different direction.

10. Fig.Construction of LCD
There are three function which make LCD.the first function is source of back light.secound
function is polarization of light source and third function is liquid crystals which change the
polarize light
To genrate the clour in LCDs colour filter is use.clour filter have primary clour such as green
,red ,blue.these colour genrate million of clour scheme.these filter is plase in face of pixal.In TFT
different capacitor and transistor is use which control the pixal of display.it has flat panel.
6.Advantages of LCDs
 Brightness. Liquid crytstal Prepared very clear bright images due to high peak resolution.it
shows very bright and clourfull picture.
 Emissions .It produce considerably lower electric, magnetic and electromegnetic feilds than
CRTs.
 Geometric distortion. Geometric curvature at native resolutions.minor distortion can occur
for other resolutions.
 Power consumption:Lcd take take less electricty .it mostly take 12 volt.it consume less than
1/3 the power of comparable CRT.It produce less heat.
 Physical aspects:LCD is thick sharp bright clour take up about 40% less desk space.
 Screen shape:Completely flat screen
 Shapness: due to native resolution highly sharp immage is produse.Color are resolution of
image is sharp.no colour bands is produce.
7.Applications:
7.1. The liquid crystal thermomete
A liquid crystal thermomete change the colour by changing the temperature.
The liquid crystal s show change .These crystals change colors from black, red, yellow, green, and
blue. The curent temperature is find.the liquid crystals change into green..if green clour is not appear
then temp becom interndiate.

11. 7.2 Optical imaging
This technique is ue for tratment of diseases,diagnosis and treatment of medical office .in these
techinque rays are passed through demage area such as tumour and facture,camera is attach to
the computre which show image on computer. ultraviolet, and infrared rays are use for detection
of diseases and image appears on secrean.
7.3 Helmets and bullet proof vests
Polymer liquid crystal is high,strong .fiexable,dense material.It is use in industry level.it is use to
make the high strength fiber.Kevlar use this material to make helmets and bullet-proof vests.this
material is light in weight but have high srength and resistance.
Ordinary polymers have no capasity to compeat the material such as steel.It is observed that long
chain polymerse have strong and high capasity then ordinary polmerce.
7.4 Battery testing strips(used by Dura Cell)
It is important property of liquid crystals,it indicates the amount of charging store in the
batter.When the electric current passing through medium it genrate heat.due to excess of heat
orientation of layer take place which change the the layers orientation to produce a colour
change.

12. 7.5 Slugs and snails(nature)
 In nature liquid crystal is also present. Slugs and snails are produce liquid crystals in the soil
.Soil particles acts as solid while mucus which secrat snails act as liquid phase it is important
application of liquid crystal.they provide moisture and wetting to the soil.they secreat mucus
which align the soil particles in specific pattren .
 Liquid crystal present in biological cell membrane.
7.6 Future Application
 Smart window
 3D display
 Synthesize biological membrane
 Computer LCD
 Use in cell phone
 LCD’s watch
The world lagest LCD is103 fit,Beijing.

13. 8. References:
1: P.G de Gennes, Port.j , 2010 “The Physics of Liquid Crystals”, ref 5.
2: M. J. Stephen, Excellent review of basic properties
3: J. P. Straley “Physics of liquid crystals”, Ref. [2].
4: D. Fincham, rotational motion of linear molecules, 1984 , 47–48.
5: http://www.slideshare.net/Nawarajintermediate/liquid-crystal-and-its-application#
6: Stegemeyer H, Blumel T, Hiltrop K, Onusseit H and Porsch F, Liq. Cryst. 1986,1-28.
7: Tanimoto K and Crooker P,1985, Phys. Rev. A 32 1893-5.
8: Tsvetkov V, Acta Physicicochim (USSR) , 1942 (16- 132).
9: van der Meer B Wand Vertogen G, Phys. Lett, 1976. 59A( 279-81).
10: Wright D C and Mermin N D, Phys. Rev, 1985. A 31 3498-500.
11:Thoen J. 1988 Phys. Rev. A 37 1754-9
12 Tsvetkov V 1942 Acta Physicicochim (USSR) 16 132
13 Tanimoto K and Crooker P P 1984 Phys. Rev. A 29 1566-7 13 Tanimoto K, Crooker P P
and Koch G C 1985 Phys. Rev. A 32 1893-5