Liquid Crystals - Types, Properties and Applications

Liquid Crystals are substances that exhibit properties between those of conventional liquids and solid crystals.
They flow like a liquid but have some degree of ordered structure.
They are most well-known for their use in liquid crystal displays (LCDs).

Types of Liquid Crystals:

Thermotropic:
- Change their phase in response to temperature.
- Nematic Phase: Molecules are oriented in the same direction but not arranged in a well-defined pattern. They have the least order and flow easily.
- Smectic Phase: Molecules are arranged in layers and can slide past each other within the layer but maintain a degree of order.
- Cholesteric (Chiral Nematic) Phase: Molecules are arranged in layers with each layer having a slightly different orientation, leading to a helical structure.
Lyotrop:
- Formed by mixing two or more substances, typically involving a solvent.
- Their phase behavior is dependent on the concentration of the components.
- Common in biological systems (e.g., cell membranes composed of lipid bilayers).

Anisotropy: Liquid crystal exhibit different properties in different directions (e.g., optical and electrical properties).
Display Technology: Used in LCD screens, where electric fields manipulate the orientation of the crystals to control light passage.
Sensors: Liquid crystals respond to changes in temperature, pressure, and chemical environment, useful in various sensing applications.