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Title: An AC Electrooptic Technique for Measuring the Flexoelectric Coefficient $\mathsf(e_1 + e_3)$ and Anchoring Energies of Nematics
Authors: Warrier, Sobha R.
Madhusudana, N.V.
Issue Date: 1997
Publisher: EDP Sciences
Citation: Journal de Physique II, 1997, Vol.7, p1789-1803
Abstract: We report an AC technique to measure both the sign and magnitude of (e1 + e3) using electrooptic measurements on a hybrid aligned nematic cell. A detailed numerical analysis of the optical signal allows us to obtain the temperature dependences of (e1 + e3), the rotational viscosity coefficient $\gamma_1$ as well as the anchoring strengths at the two surfaces. Our measurements on CCH-7 show the following interesting results. a) The extrapolation length L1 at the homeotropic surface shows a small decrease as the temperature is increased to 66 $^{\circ}$C beyond which it shows a sharp increase which we interpret as arising from a softening of the chains of the aligning ODSE layer. b) The slope of the temperature dependence of the extrapolation length $L_{\rm u}$. at the homogeneous surface changes sign around 72 $^{\circ}$C. c) (e1 + e3)/S is a constant upto 72 $^{\circ}$C and decreases rapidly beyond this temperature. The last two results are attributed to an increase in the conformational freedom between the rings of CCH-7 molecules beyond that temperature.
Description: Restricted Access. Please click on the alternative location for the open-access full text.
ISSN: 1155-4312
1286-4870 (Online)
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Copyright: (1997) Les Editions de Physique
Appears in Collections:Research Papers (SCM)

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