Who Discovered Liquid Crystals?

An Austrian botanist, Friedrich Reinitzer, working at the University of Graz, discovered this class of materials in 1888. He was working with esters of cholesterol, natural substances in plants and animals. He observed that these materials exhibit a "double melting" transition that was reversible and repeatable on heating or cooling. As the substance was heated, the crystalline solid melts to form first an optically opaque liquid that transforms to a clear liquid at a distinct temperature. A molecular model of the cholesterol molecule is shown below.

 

Reinitzer sent samples of these substances to a German Physicist, Otto Lehmann, to have crystallographic studies performed. Lehmann intuitively deduced from his data that the liquids' optical properties were due to elongated molecules that were oriented parallel to each other with their long axes. At the time, the molecular structure of cholesterol was not known yet. Systematic work to find the connection between the molecular structure of a chemical compound and the occurence of liquid crystalline behavior was started by a Chemist, Daniel Vorlander, sometime after 1900, at the University of Halle.

 

How many different liquid crystalline compounds are there?

In hindsight, a number of scientists have dealt with liquid crystalline substances but did not notice the phenomena. Over the decade after Reinitzer's discovery, about 15 compounds became known to behave like liquid crystals (LC). By 1935, about 1100 liquid crystalline substances were synthesized. Today, more than 50,000 compounds and mixtures are known to possess liquid crystalline properties.

 

Years	Number of LCs synthesized
1890s	15
1930s	1100
1990s	>50,000

 

The explosion in the discovery of liquid crystalline phases began in the 1970s with the invention of Liquid Crystal Displays (LCDs).