Discovery of LCs
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[Discovery of liquid crystals (LC)]

Between 1850 and 1888, people from different fields like chemistry, biology observed strange behavior in some materials when the temperature is approaching the melting point. W. Heintz, a German biochemist, reported in 1850 that stearin melted from a solid to a cloudy liquid at 52<C, changed at 58<C to an opaque and at 62.5<C to a clear liquid. Others reported observing blue colors when compounds synthesized from cholesterol were cooled. Biologists observed anisotropic optical behavior in "liquid" biological materials, a behavior usually expected only in the crystal phase.

In 1888, Friedrich Reinitzer, an Austrian botanist observed that there was two melting points for a certain material while he was making esters of cholesterol for studying cholesterol in plant. This material is now known as cholesteryl benzoate. He also observed birefringence and iridescent colors between these two melting points.

However, Reinitzer did not know what shall be done about this discovery; therefore he consulted with van Zepharovich, a crystallographer in Prague. van Zepharovich suggested that Reinitzer contact Otto Lehmann, a physicist in Karlsruhe, Germany, for further discussion, because Lehmann is the first to use hot stage on a polarized optical microscope, which later became the standard equipment for liquid crystal research. Following Zepharovich’s advice, Reinitzer then contacted Lehmann concerning the two-melting-points phenomenon. Their discussion by mails finally lead to the first real investigation of liquid crystals, eventually to fundamental understandings of the nature of this new phase of matter. Lehmann and Reinitzer may thus with some justification be called the grandfathers of liquid crystal science.

After the discovery, the liquid crystal research flourished. In 1922, Georges Friedel suggested a classification scheme to name different phases of liquid crystals called nematic, smectic and cholesteric, which are still used today.
Carl Oseen in Sweden worked on elastic properties of liquid crystals and his results were used on the continuum theory by England's F.C. Frank. This theory became one of the fundamental theories in liquid crystals today.
V. Freedericksz in the 1930¨s. The transition from a homogeneous to a deformed structure at some critical value of applied field strength is named Freedericksz transition due to his pioneering work in this area.
Alfred Saupe, a German physicist, later working at Kent State University, worked together with his advisor Wilhelm Maier in Karlsruhe 1958 on his thesis ("Diplomarbeit"), a molecular theory of liquid crystals not involving permanent dipoles as Max Born's theory did. This work gave rise to the Maier-Saupe Theory, another well-known basic theory of liquid crystals.

From 1945 to 1958, everything seemed slow down in the liquid crystal field. People thought they knew everything about liquid crystals and that nothing new could be expected in this area. Even worse, they were not even included in textbooks. An entire decade of growing scientists did not have contact with liquid crystals. No one could yet imagine how large a role liquid crystals would play in technical applications today.

In 1958 Glenn Brown, an American chemist, published an article in Chemical Reviews on the liquid crystal phase and subsequently sparked an international resurgence in liquid crystal research.

Pierre-Gilles de Gennes, the laureate of Nobel Prize in Physics 1991, becomes the first and so far the only person receiving this prize in the field of liquid crystals. He was awarded "for discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers".



Further Readings and References:

Y. S. Chandrasekhar, "Liquid Crystals", Cambridge University Press (1992).

P. G. de Gennes and J. Prost, "The Physics of Liquid Crystals", Oxford University Press (1995).

J. A. Castellano, "Liquid Gold: The Story Of Liquid Crystal Displays and the Creation of an Industry", World Scientific Publishing (2005)


Last update: April, 2006
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