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.
URI:	http://hdl.handle.net/2289/2914
ISSN:	0267-8292 1366-5855 (online)
Alternative Location:	http://dx.doi.org/10.1080/02678298908045691
Copyright:	1989 Taylor & Francis
Appears in Collections:	Research Papers (SCM)

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