Dielectric spectroscopy of unsymmetrical liquid crystal dimers showing wide temperature range TGBA and TGBC* phases |
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| Authors: | Abhay S Pandey M B Pandey A S Achalkumar C V Yelamaggad |
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| Institution: | 1. Material Research Laboratory , Physics Department , Ewing Christian College , Allahabad University , Allahabad‐211 003, India;2. Physics Department , Allahabad University , Allahabad‐211 002, India;3. Centre for Liquid Crystal Research , Jalahalli, Bangalore‐560 013, India |
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| Abstract: | The electrical properties of frustrated twist grain boundary (TGB) phase are a matter of curiosity. Some studies have indicated the existence of soft and Goldstone modes in TGBA and TGBC* phases respectively. However, the experimental results are still not very conclusive. In the present work, we report dielectric studies of wide temperature range TGBA and TGBC* phases of an optically active dimeric compound 4‐n‐decyloxy‐4′‐(cholesteryloxycarbonyl‐1‐butyloxy) chalcone in the frequency range of 1 Hz to 35 MHz for the planar and homeotropic anchoring of the molecules. Two different relaxation processes have been detected for the planar anchoring of molecules in the TGBA and TGBC* phases. The soft mode like behaviour is obtained due to tilt fluctuation of molecules in the megahertz region for both TGBA and TGBC* phases. Goldstone mode like behaviour due to phase fluctuation of molecules has been detected for the TGBC* phase in the low frequency region (～200–300 Hz). Activation energies for DC conductivity have also been determined for various phases of the material. |
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| Keywords: | TGB phases dielectric permittivity and anisotropy dielectric strength relaxation frequency ionic conductivity |
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