Lehmann started a systematic study, first of cholesteryl benzoate, and then of related compounds which exhibited the double-melting phenomenon.

The research was continued by Lehmann, who realized that he had encountered a new phenomenon and was in a position to investigate it: In his postdoctoral years he had acquired expertise in crystallography and microscopy. Д«y that time, Reinitzer had discovered and described three important features of cholesteric liquid crystals (the name coined by Otto Lehmann in 1904): the existence of two melting points, the reflection of circularly polarized light, and the ability to rotate the polarization direction of light.ДЄfter his accidental discovery, Reinitzer did not pursue studying liquid crystals further. Reinitzer presented his results, with credits to Lehmann and von Zepharovich, at a meeting of the Vienna Chemical Society on May 3, 1888. The exchange of letters with Lehmann ended on April 24, with many questions unanswered. Reinitzer's Viennese colleague von Zepharovich also indicated that the intermediate 'fluid' was crystalline. Lehmann examined the intermediate cloudy fluid, and reported seeing crystallites. Seeking help from a physicist, on March 14, 1888, he wrote to Otto Lehmann, at that time a Privatdozent in Aachen. At 145.5В вЊ (293.9В вЏ) it melts into a cloudy liquid, and at 178.5В вЊ (353.3В вЏ) it melts again and the cloudy liquid becomes clear. He found that cholesteryl benzoate does not melt in the same manner as other compounds, but has two melting points. Reinitzer perceived that color changes in a derivative cholesteryl benzoate were not the most peculiar feature.Д¬hemical structure of cholesteryl benzoate molecule Previously, other researchers had observed distinct color effects when cooling cholesterol derivatives just above the freezing point, but had not associated it with a new phenomenon. In 1888, Austrian botanical physiologist Friedrich Reinitzer, working at the Karl-Ferdinands-UniversitГ¤t, examined the physico-chemical properties of various derivatives of cholesterol which now belong to the class of materials known as cholesteric liquid crystals.

8.1 Electric and magnetic field effects.

8 External influences on liquid crystals.

7 Theoretical treatment of liquid crystals.

3.1.3 Chiral phases or twisted nematics.

2 Design of liquid crystalline materials.

Other well-known examples of liquid crystals are solutions of soap and various related detergents, as well as the tobacco mosaic virus, and some clays. For example, many proteins and cell membranes are liquid crystals. Lyotropic liquid-crystalline phases are abundant in living systems but can also be found in the mineral world. Widespread liquid-crystal displays (LCD) use liquid crystals. Metallotropic LCs are composed of both organic and inorganic molecules their liquid-crystal transition depends not only on temperature and concentration, but also on the inorganic-organic composition ratio.Д®xamples of liquid crystals can be found both in the natural world and in technological applications. Lyotropic LCs exhibit phase transitions as a function of both temperature and concentration of the liquid-crystal molecules in a solvent (typically water). Thermotropic LCs exhibit a phase transition into the liquid-crystal phase as temperature is changed.

Thermotropic and lyotropic liquid crystals consist mostly of organic molecules, although a few minerals are also known. Liquid crystals can be divided into thermotropic, lyotropic and metallotropic phases. LC materials may not always be in a liquid-crystal state of matter (just as water may turn into ice or water vapor). Within a domain, however, the molecules are well ordered. The contrasting areas in the textures correspond to domains where the liquid-crystal molecules are oriented in different directions. There are many different types of liquid-crystal phases, which can be distinguished by their different optical properties (such as textures). For instance, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. Liquid crystal (LC) is a state of matter that has properties between those of conventional liquids and those of solid crystals.

Liquid notes re compose