Lehmann effect in compensated cholesteric liquid crystals

OFFPRINT Direct measurement of the thermomechanical Lehmann coefficient in a compensated cholesteric liquid crystal

The thermomechanical Lehmann coefficient ν is directly measured as a function of temperature in a compensated cholesteric liquid crystal. The method consists of observing the continuous rotation of the director in samples treated for planar sliding anchoring when a temperature gradient is applied perpendicularly to the director. The main result is that there is no relationship between the Lehma...

Wetting of cholesteric liquid crystals.

We investigate theoretically the wetting properties of cholesteric liquid crystals at a planar substrate. If the properties of substrate and of the interface are such that the cholesteric layers are not distorted, the wetting properties are similar to those of a nematic liquid crystal. If, on the other hand, the anchoring conditions force the distortion of the liquid crystal layers the wetting ...

Hydrodynamic instabilities in active cholesteric liquid crystals.

We describe the basic properties and consequences of introducing active stresses, with principal direction along the local director, in cholesteric liquid crystals. The helical ground state is found to be linearly unstable to extensile stresses, without threshold in the limit of infinite system size, whereas contractile stresses are hydrodynamically screened by the cholesteric elasticity to giv...

Diffuso-mechanical coupling in cholesteric liquid crystals

2014 It has been observed that in cholesterics shear flow induces a transverse drift of small particles suspended in the liquid crystal. Quantitative measurements of the drift velocity are presented. The effect is interpreted using the analogy of the thermomechanical coupling, predicted for cholesterics. J. Physique LETTRES 42 ( 1981 ) L-41 L-43 Classification Physics Abstracts 61.30 15 JANVIER...

Cholesteric to cholesteric phase transitions in liquid crystals