The two key names in the story of the discovery of liquid crystals were Freidrich Reinitzer - the first to observe the dual melting point, and George Gray, the first to synthesize a practical liquid crystal.
Both of these individuals would acknowledge enormous intellectual and practical debts to immediate colleagues who helped and inspired them in there lab work. They would also both recognise the importance of a broader network of key individuals who made related discoveries which allowed them to succeed. These are just four of the key figures:
Reinitzer made the initial discovery or observations which brought liquid crystals to scientific attention. However, it is unreasonable to pretend that he had an explanation for the phenomenon - he didn’t.
In fact, Reinitzer had no explanation of what he’d seen. However Reinitzer was in correspondence with Lehmann during 1888 and Lehmann made several breakthroughs. It was Lehmann who did most of the work with polarized light.
Lehman was also the first to propose that the behaviour of liquid crystals was probably related to their shape, and was the first to propose that a new state of matter had been discovered. He first called it crystalline liquid - only later changing his mind and calling it ‘liquid crystal’.
Cholesteryl benzoate is just one amongst hundreds of thousands of liquid crystals. One important break though followed the work of Friedel in 1992. He recognised that there were three main types of organsation of the molecules which form liquid crystals, the three types of organisation are often called phases, or mesophases:
- nematic -(after the Greek work nematos - meaning thread-like). In this phase the molecules are aligned in one general direction but have little other organisation. A good analogy is to think of a tin of long pins. If you shake them, then after a while they all begin to align in the same direction. They can all move, and move around each other - but they show a broad common alignment.
- cholesteric - This is similar to the nematic organisation. However, it’s as if the direction the pins are facing changes gradually within the space they occupy. Another way to imagine it is as if there is a gradual twist in their arrangement..
- smectic - (which means ‘soap like’) You could imagine this phase in terms of the pins again. But now the pins are additionally arranged in layers, one above the other. It’s as if the pins were still being shaken and organised as in the nematic phase - but pins in these phases are then laid out upon separate shelves one above the other.
Actually, there are several more types of smectic organisation.
Schadt and Helfrich
Modern liquid crystal displays are based on the ‘twisted nematic’ effect and this was invented by Schadt and Helfrich in 1971. This also provides the background to more advanced displays.