Flow properties, chiral nematics

The flow properties of other liquid crystals, such as chiral nematics (i.e.. cholesterics). smectics C, and hexagonal phases, are even more poorly understood. 

The most important multicolour display technology in current use involves liquid crystal displays (LCDs), which overtook CRTs in popularity around the mid-2000s. Liquid crystals (LCs), commonly referred to as the fourth state of matter, are materials that are intermediate in character between the crystalline solid and liquid states.Unlike normal isotropic liquids in which the molecules essentially adopt a randomised orientation, liquid crystals show some time-averaged positional orientation of the molecules. In this sense, they resemble solid crystalline materials, although they retain most of the properties of liquids, notably the ability to flow. They are formed most commonly from molecules with rod-like geometry, which are referred to as calamitic. These molecules may orientate in various ways to form different types of LC phases [mesophases). There are three main mesophase types smectic, nematic and chiral nematic. In the smectic mesophase, as illustrated in Figure 11.1(a), the molecules are arranged in raft-like layers with their molecular axes parallel. These layers can pass over each other as the material flows. In the... 

In this context, literature [90] states that at room temperature, acetoxypropyl cellulose exhibits both chiral nematic phases—the lyotropic and the termotropic one. When subjected to specific conditions of shear flow, the cellulose derivative cholesteric liquid crystal suffers transformations, such as cholesteric helix and cholesteric-to-nematic transition. The films prepared from anisotropic solutions of termotropic acetoxypropyl cellulose in an isotropic solvent exhibit anisotropic mechanical properties, generated by the molecular orientation of the solution under shear stress. Thus, liquid crystalline solutions give rise to films with anisotropic mechanical properties the films are brittle when stretched parallel to the shear direction and ductile when stretched perpendicular to it. 

M ribbons, chromonics 996 Mach-Zehnder interferometer 132 macrocyeles, hydrocarbon cores 719 f macrocyclic complexes, metallomesogens 926 macroscopic flow, chiral nematics 379 macroscopic polarization, ferroelectrics 541 ff macroscopic properties... 

Dependences of properties of chiral nematic phases on achiral variables such as pressure, temperature, electric and magnetic fields, flow and others are not considered in this Datareview. For this information we refer to [1,2]. Also optical, electro-optical, and magneto-optical properties like optical rotation, CD, and selective reflection, in the region where the wavelength is or is not in the length-scale... 

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