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Title: An experimental investigation of electromechanical coupling in cholesteric liquid crystals
Authors: Madhusudana, N.V.
Pratibha, R.
Issue Date: 1989
Publisher: Taylor & Francis
Citation: Liquid Crystals, 1989, Vol.5, 1827 - 1840
Abstract: Cholesteric liquid crystals which have a helical arrangement of oriented chiral molecules are expected to show novel cross couplings between fluxes and forces. The most convincing demonstration of these couplings is through a dynamical effect on the structure. Though Lehmann found a rotation of the structure under a temperature gradient in 1900, there has been no subsequent experiment confirming the same. We argue that it is very difficult to obtain a sufficiently weak anchoring of the director at the solid-cholesteric interface which is a necessary condition for the occurrence of Lehmann rotation. In order to achieve a practically zero anchoring energy at the surface, we have devised a simple technique of floating essentially flat cholesteric drops in the isotropic phase. Using this configuration we study the electromechanical coupling which produces a rotation of the structure under the action of a DC electric field. Using measurements on samples with different values of the pitch the relevant electromechanical coefficient of the materials investigated is found to satisfy the relation vE = -0·6 × 10-12(q/m-1)J m-2, where q is the wavevector of the helix, whose sign is positive (negative) for a right (left) handed structure, confirming that vE is hydrodynamic in origin.
Description: Restricted Access.
ISSN: 0267-8292
1366-5855 (online)
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Copyright: 1989 Taylor & Francis
Appears in Collections:Research Papers (SCM)

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