TABLE OF CONTENTS In 1888, Friedrich Reinitzer, an Austrian botanist, was investigating the melting transition of an organic compound related to cholesterol, when he saw something very curious (Reinitzer 1888). The solid melted into a cloudy liquid at 145.5 C, but then "melted" again into a clear liquid at 178.5 C! Reinitzer described his observation in a letter to Otto Lehman, a German physicist, who confirmed it using a polarizing microscope to which he had attached a hot stage (Lehmann 1890). Lehmann found other substances with similar behavior, and he and Reinitzer recognized that the cloudy liquid, which was also birefringent, was a new state of matter that Lehmann eventually called a liquid crystal. Liquid crystals were so beautiful to look at in a polarizing microscope, and so intriguing in their properties, that although for 100 years they had no practical uses, they were studied intently by several determined scientists, who learned many of their secrets. Since the 1960s, the knowledge they extracted has become very profitable: Liquid crystals are now used in almost all lap-top computers and in many other applications.
Liquid crystals derive both their beauty and their usefulness from their ordered, yet liquid, state. At rest, they possess at least some orientational order at rest, but lack the full three-dimensional positional order of solid crystals. Orientational order implies that the molecules tend to point in the same direction, while positional order implies that the molecules' centers of mass tend to lie on lattice points. Spherically symmetric molecules,...
