Orientation in Liquid Crystal Solutions

Liquid crystals (LCs) possess properties of the matter between that of a crystalline and an isotropic liquid. Many of the mechanical properties of liquid, such as high 

The word nematic comes from the Greek word vripa (nema), which means thread. This term originates from the thread-like topological defects observed in nematics, which are formally called disclinations. Nematics also exhibit so-called hedgehog topological defects. 

Nematics have fluidity similar to that of ordinary (isotropic) liquids but they can be easily aligned by an external magnetic or electric field. Aligned nanatics have the optical properties of a uniaxial crystal and this makes them extranely useful in liquid crystal displays (LCDs). 

FIGURE 1.10 Structure of the nematic liquid crystal of the alkylbicyclohexyl type. 

The principal advantage of the methods of orientation in nematic solvents, compared to the technique in a poly(ethylene) matrix, is the facile and prompt preparation of samples as well as thdr stability on storage. Moreover, the use of cuvettes with fixed thickness of the layer makes it possible to compensate for the inherent absorption bands of the liquid crystal, except for those at 2800 to 3000 cm . The manipulation, however, is not always successful, since there is the possibility for both the solution and pure nematic to have different degrees of orientation. The latter would, eventually, result in the residual absorption, observed in the reduced spectra and caused by solvent molecules. 

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