History of Liquid Crystals

Abstract

The mesomorphic states such as liquid crystalline, discotic or carbonaceous, plastic, paracrystalline and viscous crystalline mesophases were classified and discussed on the light of the characteristics of the states. Historical developments of liquid crystals were reviewed briefly from their discovery to technical applications like a display technology, covering scientific, medical and technological researches and applications : Mesogenic compounds were used as solvents for NMR, ESR and optical spectroscopies such as IR and UV, and chemical reactions such as degradation, Claisen rearrangement, photoreaction, polymerization, hydrolysis, oxidation or reduction, carbonization and photoelectrochemical reaction, and also in gas-liquid chromatography. Technical application included many types of displays such as digital, signal, advertising, analog, color displays, image converter and large-area screens. Liquid crystals were used in coherence optics and for medical applications such as diagnoses of vascular diseases and cancer, localizing the placenta, pharmacological tests and skin grafting. The first period from the middle of the 19th century until 1922 comprised the discovery of liquid crystals and work of predominantly descriptive character, followed with the first theoretical work and the foundation of systematology of the phase. The second was known with the development of quantitative theory and the investigation of the effects of outer forces and fields on liquid crystals, beginning from 1922 to 1945. Severe interruption and even complete collapse of international communication continued until the end of the war. During the last period from 1945 technical application and scientific research made a strong revival which lasts until today, achieved successfully the combination of material (liquid crystals), energy and systems (electronics).