Why are Liquid Crystals so Interesting?

Liquid Crystals

Liquid crystals are used in many displays. They are important because of the richness of structures and transitions. Liquid crystals are relatively large regions of molecules which point in the same direction, and so have a structure analogous to ordinary crystals. Lehmann first referred to them as flowing crystals and later used the term “liquid crystals”.

Liquid crystals are best known for their use in displays in which an electric field darkens parts of the display to produce numbers letters or patterns by rotating some of the molecules away from the direction of their neighbors. The liquid crystals obtained by two methods called thermotropics and lyotropics.

The process of liquid crystalline solutions and melts reveals some interesting facts. The most important observation is that fibers and injection molded specimens are highly oriented. Molecular orientation in the solid state comes directly from flow induced orientation since no further drawing of the specimens occurs. Because of the direct correlation of flow history to structure property relations and understanding of the rheological properties of these systems is essential.

Liquid crystals can be composed both of polar and apolar molecules. An important fact in connection with polar substances is that in uniaxial phases there is no polar ordering of the molecules. In addition, liquid crystals are anisotropic materials, hence their linear optical properties are determined by a symmetrical dielectric tensor rather than a scalar refractive index.