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31 January 2008 Extraordinary properties of nematic phases of bent-core liquid crystals
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Abstract
We briefly review systematic and comprehensive studies on several chlorine-substituted bent-core liquid crystal materials in their nematic phases. The results, in comparison to rod-shaped molecules, are both extraordinary and technologically significant. Specifically: a) Electrohydrodynamic instabilities provide unique patterns including well defined, periodic stripes and optically isotropic structures. b) Rheological measurements using different probe techniques (dynamic light scattering, pulsed magnetic field, electrorotation) reveal that the ratio of the flow and rotational viscosities are over two orders of magnitudes larger in bentcore than in calamitic materials which proves that the molecule shape and not its size is responsible for this behaviour. c) Giant flexoelectric response, as measured by dynamic light scattering and by directly probing the induced current when the material is subject to oscillatory bend deformation, turns out to be more than three orders of magnitude larger than in calamitics and 50 times larger than molecular shape considerations alone would predict. The magnitude of this effect renders these materials as promising candidates for efficient conversion between mechanical and electrical energy. d) The converse of this effect when the bent-core material sandwiched between plastic substrates 4 times thicker than the liquid crystal material provided displacements in the range of 100nm that is sensitive to the polarity of the applied field thus suggesting applications as beam steering and precision motion controls.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. Jákli, M. Chambers, J. Harden, M. Madhabi, R. Teeling, J. Kim, Q. Li, G. G. Nair, N. Éber, K. Fodor-Csorba, J. T. Gleeson, and S. Sprunt "Extraordinary properties of nematic phases of bent-core liquid crystals", Proc. SPIE 6911, Emerging Liquid Crystal Technologies III, 691105 (31 January 2008); https://doi.org/10.1117/12.768866
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