Role of dopants on the electro-optic effect in nematic liquid crystals aligned with doped polypyrrole

In order to estimate electro-optical response times, measurements of the transmitted light intensity through positive uniaxial nematic thin films in planar alignment have been performed. Very fast relaxation times were experimentally found for nematic samples aligned with conductive polymers, namely...

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Bibliographic Details
Published in:Journal of applied physics 2011-06, Vol.109 (12), p.124905-124905-5
Main Authors: Raicopol, Matei, Dascalu, Constanta, Atasiei, Ruxandra, Ionescu, Andrei Th
Format: Article
Language:English
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Summary:In order to estimate electro-optical response times, measurements of the transmitted light intensity through positive uniaxial nematic thin films in planar alignment have been performed. Very fast relaxation times were experimentally found for nematic samples aligned with conductive polymers, namely, polypyrrole doped with 5 types of anions having different molecular sizes and geometries. Using undoped polypyrrole alignment layers, slower electro-optical responses were obtained. Given that the improvement in the relaxation times is induced by the presence of the anions in the polypyrrole films, the increasing of the total restoring torque of the nematic molecules to the confining surfaces-responsible for the short relaxation times-is related to the charges accumulated at the nematic-conductive polymer interface.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3597824