The World of Liquid Crystal
Department of Chemistry
Yonsei University
Moon-Gun Choi
1.1
Discovery of Liquid Crystals
 The end of the 19th century
Austrian botanist Friedrich Reinitzer
 to study the role of cholesterol in plants
1.2
Discovery of Liquid Crystals
 Otto Lehmann, examined the cloudy ‘in-between phase’
“mesophase”
1.3
Identifying a Liquid Crystal
 Polarizing Optical Microscope
 DSC(Differential Scanning Calorimeter)
0
50
100
150
200
250
1.4
Why Liquid Crystals Form?
Uneven distribution of electrons in the molecule
 Intermolecular forces
 Strong enough to cause the molecule line up in the
same overall direction but not strong enough to hold
them firmly in one place
(over a certain range of temperatures)
1.5
Why Liquid Crystals Form?
 The Fourth State of Matter
1.6
Types of Liquid Crystals
1.7
Liquid Crystal Display Industry
1.8
The Chemistry of Liquid Crystals
 Understand which factors of the molecular structure
give rise to LC behavior.
 Tailor the molecules they made to give them the
properties required for useful applications.
 Align parallel to an electric field
 Liquid crystal phase over a large temperature range
 High chemical stability
1.9
The Liquid Crystals that Revolutionized the Display Industry
1.10
The Polymer Dispersed Liquid Crystal(PDLC) Display
(SMART WINDOW)
1.11
Discotic Liquid Crystal Materials and Molecular Wires
1.12
Types of Columnar LC Phases
1.13
Schematic Representation of Five Discotic Phases
1.14
Various phases of calamatics and discotics molecules
1.15
Lyotropic Liquid Crystal
LC behavior depends
upon the concentration
in solution
>
1.16
Thermotropic Liquid Crystal
LC behavior depends upon the temperature
1.17
Properties of Metallomesogen
 Various 3-D Structure
 Ferroelectric Property
 NLO Property
 Paramagnetic Property
by forming stable radical
1.18
Publications on Metallomesogen
1.19
Examples of Metallomesogen
1.20
Examples of Metallomesogen
H 2n+ 1 C n O
H 2n+ 1 C n O
COCl
CO
CO
2
Fe
+
OH
2
COCl
H 2n+ 1 C n O
NEt 3
CH 2 Cl 2
OC n H 2n+ 1
CO
H 2n+ 1 C n O
H 2n+ 1 C n O
2
CO
2
O 2C
OC n H 2n+ 1
Fe
CO
2
O 2C
Crystal
Bicontinuous
cubic (bcc)
Columnar
Isotropic liquid
OC n H 2n+ 1
O 2C
o
Temperature( C )
H 2n+ 1 C n O
4 a ~ g (a :n = 6 , b :n = 8 , c :n = 1 0 , d :n = 1 2 , e :n = 1 4 , f:n = 1 6 , g :n = 1 8 )
Fe
1.21
Applications of Liquid Crystals
1.22
Applications of LC Display Device
1.23
Ferroelectric, Antiferroelectric LC
 Ferroelectric
 permanent dipole moment in the
absence of an external electric
filed.
 Ferroelectricity of smectic C*
 switch very quickly (μs vs ms)
 Antiferroelectric
 tilt direction alternates between
layers
1.24
Liquid Crystal Polymers
1.25
Soaps and Detergents as an Example of LC
1.26
Liquid Crystals in Nature
1.27
Semi-flexible Main-Chain Polymer
1.28
Side-Group LC Polymers for Optical Memories
1.29
Liquid Crystals and Life
1.30
Liquid Crystals and Life
1.31