Historical Development of Polymer Liquid Crystals

The liquid crystalline state was first observed by an Austrian botanist, Friedrich Reintzer, in 1888, when he noted that cholesteryl esters formed opaque liquids on 

Liquid crystals can be divided into two main classes those similar to the cho-lestrayl derivatives, whose liquid crystalline phases are formed when the pure compound is heated, arc called thermotropicy and those where the hquid crystalline phase forms when the molecules are mixed with a solvent are referred to as lyotropic. The thermotropic class also includes enantiotropic types, whae the liquid crystalline phases can be seen on both the heating and the cooling cycles, and monotropic types, where the mesophase is stable only on supercooling from the isotropic melt. 

Continued investigations led to the identification of three main types of mesophase a smectic state smegma in Greek, meaning soap), a nematic state nema in Greek, meaning thread), and a cholesteric state observed in systrans containing molecules with a chiral craitCT. 

A Selection of Small Molecule Mesogens and the Associated Liquid Crystalline Behavior 

Note Phases are shown as k = eiystal phase N = nematie phase N = chiral nematic phase i = isotropic phase. The temperature of the transition from one to another is represented by the number between the phases on heating. That is, k to N at 106°C and N to i at 117°C. 

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