Download Scientific I 2003

Liquid Crystals
The Fourth State of Matter?
Dr. Vance Williams
Department of Chemistry
Simon Fraser University
Liquid Crystals: Some Applications
Liquid Crystals: Not An Oxymoron
Most crystals are solids that are ordered in 3
dimensions.
Most liquids are completely disordered.
Some liquids are ordered in 1 or 2 dimensions
(and therefore are “crystalline”).
Liquid Crystals
Smectic
Nematic
Columnar
Liquid Crystals: History
The first liquid crystal was discovered
in 1888 when Friedrich Reinitzer
noticed that a compound he was
studying exhibited two melting points;
one at 145 °C and a second at 178 °C.
1857-1927
Cholesteric Liquid Crystals
cholesterol
H
H
H
HO
H
O
H
O
H
cholesteryl benzoate
Thermochromism
Mood Rings and Thermometers
molecules
form a helix...
T
…this helix gets tighter as the temperature increases
LCDs and Polarized Light
Polarized Light
Polarized Light
Polarized Light
Inserting an
organized,
“birefringent”
material between
the polarizers
allows some light to
be transmitted.
Phases Under a Microscope
All imaged
viewed through
cross-polarized
light.
Welding Masks
Solar cell
Welding Masks
Solar cell
“Smart” Windows
“Smart” Windows
Pressure Sensors
Pressure Sensors
Natural Liquid Crystals:
DNA
Vance Williams
Department of Chemistry
Simon Fraser University
[email protected]
www.sfu.ca/chemistry/faculty/Williams/VEW1.htm
www.sfu.ca/chemistry