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The image shows a rotation of the director about 180° in a cholesteric phase. The corresponding distance is the half-pitch, p/2. A cholesteric liquid-crystal display (ChLCD) is a display containing a liquid crystal with a helical structure and which is therefore chiral. Cholesteric liquid crystals are also known as chiral nematic liquid ...
However, some liquid crystals are biaxial nematic, meaning that in addition to orienting their long axis, they also orient along a secondary axis. [29] Nematic crystals have fluidity similar to that of ordinary (isotropic) liquids but they can be easily aligned by an external magnetic or electric field.
The distortion free energy density in a nematic liquid crystal is a measure of the increase in the Helmholtz free energy per unit volume due to deviations in the orientational ordering away from a uniformly aligned nematic director configuration. The total free energy density for a nematic is therefore given by:
It is a liquid crystal material forming cholesteric liquid crystals with helical structure. It can be used with cholesteryl nonanoate and cholesteryl oleyl carbonate in some thermochromic liquid crystals. It is used in some hair colors, make-ups, and some other cosmetic preparations. [1]
A blue phase mode LCD is a liquid crystal display (LCD) technology that uses highly twisted cholesteric phases in a blue phase.It was first proposed in 2007 to obtain a better display of moving images with, for example, frame rates of 100–120 Hz to improve the temporal response of LCDs. [1]
The molecular design approach of Martin Schadt and his team has led to the discovery, patenting and production of the following commercially important liquid crystal classes: alkyl cyano Schiff'bases and esters (1971), [2] phenyl-pyrimidines (1977), alkenyl liquid crystals which have become key for all state-of-the-art high-information content ...
Liquid crystals with low molecular weight can be mixed with high molecular weight polymers, followed by phase-separation to form a kind of spongy matrix filled with LC droplets. An external electric field can align the LC to match its index with that of the polymer matrix, switching that cell from a milky (scattering) state to a clear ...
Distributed feedback lasing using Bragg reflection of a periodic structure instead of external mirrors was first proposed in 1971, [3] predicted theoretically with cholesteric liquid crystals in 1978, [4] achieved experimentally in 1980, [5] and explained in terms of a photonic band gap in 1998.