Liquid Crystals

Liquid crystals are a state of matter that exhibit properties between those of conventional liquids and those of solid crystals.
They have the fluidity of a liquid, but also show a degree of ordered structure – the molecules in a liquid crystal might flow and move around, yet they also maintain a certain alignment with each other.

Structures of Liquid Crystals

In liquid crystals, the molecules are anisotropic, which means they have a different behaviour in one direction compared to another. This causes them to align in specific ways.
There are two main types of liquid crystal phases, namely nematic and smectic, distinguished by their different degrees of ordering of the molecules.
A nematic phase is the simplest form of liquid crystal, wherein the molecules have positional disorder, but have uniform alignment in a particular direction.
In a smectic phase, the molecules also show a certain degree of positional order, either in layers or in more complex structures.

Liquid crystals are used widely in liquid crystal displays (LCDs), which are lightweight, compact, and use less power than other display technologies.
In an LCD, the orientation of the liquid crystal molecules is controlled by an electric field, which allows them to manipulate light to create images.
The ability of liquid crystals to respond to changes in temperature and electric fields makes them suitable for use in a variety of other applications as well - in thermometers, sensors and in optical imaging due to their birefringence properties.

Liquid crystal polymers are a type of aromatic polyester where the polymer chains have a high degree of orientational order due to the rod-like nature of the molecules.
They possess superior properties such as high strength, high stiffness, good dimensional stability, and excellent heat resistance, making them suitable for use in specialised applications like electronics and aerospace.
However, these polymers are typically more difficult and expensive to process than common plastics, which can limit their widespread use.