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A4 Liquid Crystals (LCs)
Liquid crystals or LCs are fluids that have physical properties* that depend on the orientation of their molecules on some fixed axis in the material (*electrical, optical, elasticity).
The molecules LCs are often rod-shaped and polar and they generally point in the same direction. They remain pointing in one direction when the LC flows.
- Thermotropic LC materials are pure substances that show LC behaviour over a range of temperatures.
- Lyotropic LC are solutions that show LC state over a certain range of concentrations.
- Nematic LC phase is characterised by rod-shaped molecules (like straws or dry spaghetti) which are randomly distributed but, on average, align themselves in one direction.
Figure 4.1 Liquid crystals
Figure 4.1 shows three examples:
- Thermotropic: like dry, uncooked spaghetti. All tightly packed, aligned.
- Nematic: Loosely packed spaghetti, random, same direction.
- Random: Like a lot of spaghetti dropped on a table. No crystallinity, all directions.