Electron nematics

The factors Kn are elastic constants for the nematic phase and Icb is the Boltzmann constant. Therefore a combination of molecular electronic structure, orientational order and continuum elasticity are all involved in determining the flexoelectric polarisation. Polarisation can also be produced in the presence of an average gradient in the density of quadrupoles. This is... 

It can be safely predicted that applications of liquid crystals will expand in the future to more and more sophisticated areas of electronics. Potential applications of ferroelectric liquid crystals (e.g. fast shutters, complex multiplexed displays) are particularly exciting. The only LC that can show ferroelectric property is the chiral smectic C. Viable ferroelectric displays have however not yet materialized. Antifer-roelectric phases may also have good potential in display applications. Supertwisted nematic displays of twist artgles of around 240° and materials with low viscosity which respond relatively fast, have found considerable application. Another development is the polymer dispersed liquid crystal display in which small nematic droplets ( 2 gm in diameter) are formed in a polymer matrix. Liquid crystalline elastomers with novel physical properties would have many applications. 

From a DSC scan of the homopolymer of PHBA one can observe a major endotherm at 350 °C and a much smaller one at 445 °C (see Fig. 3) [29], The first transition has been examined by electron diffraction [27-30], X-ray diffraction [28] and proton and 13CNMR [30]. Additional insights have been provided by synthesizing much lower molecular weight samples which permit study of these transitions at appreciably lower temperatures [29]. These low molar mass homopolymers can also go into a nematic phase under a modest shear. 

Fig. 2 (a) Transmission electron microscopy (TEM) image of a disc-like beidellite clay sample (sizes of the platelets range from 69 to 480 nm in diameter), and (b) lyotropic nematic phase of an aqueous suspension of the same beidellite sample at an ionic strength of 10 4 mol L-1 ( = 0.5%) observed between crossed polarizers [263], (Copyright 2009, American Chemical Society)... 

A purely organic chiral nitroxide which shows liquid crystalline behaviour as well as intriguing magnetic properties and a dependence on the enantiomeric nature has been reported [180]. The reason for studying the compounds was to increase the sensitivity of mesophases to magnetic and electric fields. The racemic modification of the radical, which displays a nematic phase, proved to be more sensitive to alignment than the cholesteric phase with the enantiomers present. It was proposed that the compounds may also be used to study the dynamic nature of mesophases by electron paramagnetic resonance spectroscopy. 

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