Electromechanical effect in cholesteric mixtures with a compensation temperature

Abstract

An electromechanical effect arises in cholesteric (N*) liquid crystals due to a cross-coupling between fluxes and forces specific to chiral systems. We recently described an experiment to study this effect on samples with fixed boundary conditions. Here, we have derived the basic theoretical expressions relevant to this experiment. We have now used this technique to record the electromechanical signal across the compensation temperature of cholesteric mixtures consisting of cholesteryl chloride, 4'-heptyl-4-cyanobiphenyl and 2-cyano-4-heptylphenyl 4'-pentylbiphenyl-4-carboxylate. The sign of the electromechanical signal changes at the compensation point, clearly demonstrating the macroscopic origin of this effect.19