Liquid crystals have properties between liquids and crystalline solids. They are made up of long, rod-shaped organic molecules that are arranged parallel to each other but can flow like liquids. There are three main types of liquid crystals - nematic have molecules arranged parallel but able to slide, smectic have molecules in parallel layers that can slide, and cholesteric form spiral structures as the layers slide. Liquid crystals have numerous applications, including digital displays where changing the crystal arrangement causes opacity and transparency, monitoring body temperature where color changes correspond to temperature, and LCD displays which use their light modulating properties.

1. Liquid Crystal
Types and Applications

2. Liquid Crystal
• Some organic molecules do not melt to give liquid directly
• They pass through intermediate state known as ‘liquid crystal state’
• These substance have long rod-shaped molecules
• E.g. p-oxyanisole
• Liquid crystal have structure between liquid and crystalline solid.
• As Liquid molecules can move randomly and solid crystal have ordered and fixed
arrangement while liquid crystals are arranged parallel to each other and they
can flow.
• Hence, liquid crystals have fluidity of liquid and optical property of solid

3. Types of liquid crystals
• Nematic liquid crystal: They
have molecules parallel to each
other like soda straw but they
are free to slide or roll
individually
• Smectic liquid crystal: The
molecules in this type are also
arranged parallel but these are
arranged in layers. The layers can
slide on each other.
• Cholesteric liquid crystal: Like
nemetic they also have
molecules parallel but arranged
in layers. Due to sliding of layers
it form spiral structure.

4. Applications • Digital Number display:
When liquid crystal is kept
between electrodes the
change in arrangement of
crystal make it opaque …
transparency return when
current is removed
• Monitoring body
temperature: Cholesteric
liquid crystal diffract light
differently. As temperature
changes colour of reflected
light changes
correspondingly.
• Liquid-crystal display (LCD):
It is a flat panel display,
electronic visual display, or
video display that uses the
light modulating properties
of liquid crystals

5. Reference
• Essentials of Physical Chemistry by Arun Bahl , BS Bahl and GD Tuli