Today's KNOWLEDGE Share
Liquid Crystal Polymers
LIQUID CRYSTALS: DISCOVERY
The origin of liquid crystal study is typically traced back to Austrian chemist and botanist Friedrich Reinitzer. In 1888, he observed and later wrote about the strange behavior of a solid after exposing it to changing temperatures. Using solid cholesteryl benzoate,Reinitzer noticed that at one temperature the solid became a hazy liquid,yet at a higher temperature, the hazy liquid became clear. When cooling the clear liquid, again Reinitzer saw the liquid pass through two different color forms before returning to the original white solid with which he began . Reinitzer had observed two different melting points for the same material – a phenomenon which should not exist. Perplexed by his discovery, Reinitzer forwarded the solid white material along with his findings to Otto Lehmann, a physicist working out of Aachen in what is now present day Germany.
Lehmann was better equipped to study the material than Reinitzer and expanded upon Reinitzer’s work. Lehmann placed the material which he had received from Reinitzer on a microscope equipped with a heat stage and observed the material while heating it . Lehmann observed the first (intermediate) hazy liquid as the white solid melted just as Reinitzer had. He described seeing crystallites multiple small crystalline formations with irregular borders. Lehmann realized that this first intermediate fluid appeared to be crystalline in nature and that it must in fact be a new state of matter.
After further studying and refining his ideas, Lehmann named his discovery a liquid crystal . Lehmann’s (and Reinitzer’s) observation received significant attention at the time, particularly after Lehmann published his findings in 1900. Indeed, by the early twentieth century nearly 200 other compounds were found to show liquid crystal behavior. However, after this initial attention, no practicable application for this new discovery was forthcoming, and interest in this new area of science soon waned. While Reinitzer and Lehmann are routinely given note as the originators of liquid crystal science, they were also likely aware of earlier work by fellow German Wilhelm Heintz. This highly published and productive chemist had done significant work on fatty acids. By 1850, Heintz had noted that certain natural fats had two different melting points. His observations were nearly identical to Reinitzer’s and Lehmann’s: As Heintz raised the temperature of the fat substance he was analyzing, the substance first became cloudy, then fully opaque. Finally, the substance turned completely clear with continued heating .
Just as Reinitzer’s and Lehmann’s official discovery in time garnered no real appreciation, so was the case with Heintz’s observation on two melting points for a single substance. This observation of two melting points, however, would later become fundamental to identifying a liquid crystal.
source: Zeus Industrial Products, Inc.
