Synthesis and Characterization of Bent Liquid Crystal Phases by Microscopy, Calorimetry, Spontaneous Polarization and Low-Frequency Dielectric Relaxation Studies in Bent-7

Pallavajhula, V C and Srinivasulu, M and Pisipati, V G K M and Potukuchi, D M (2007) Synthesis and Characterization of Bent Liquid Crystal Phases by Microscopy, Calorimetry, Spontaneous Polarization and Low-Frequency Dielectric Relaxation Studies in Bent-7. Ferroelectrics, 361 (1). pp. 45-64. ISSN 1563-5112

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Abstract

Synthesis of the bent-shaped (or �-shaped) achiral liquid crystal Bent 7, viz., 1,3-phenylene bis(4-heptyloxy benzoate) with resorcinol as central moiety is reported. Supra molecular formation is confirmed by KBr solid state IR spectra. Polarized Thermal Microscopy(TM), Differential Scanning Calorimetry (DSC) and Spontaneous Polarization(PS) experiments infer a bivariant monotropic (cooling), phase sequence viz., Isotropic→B2(FE)→B5(AF)→solid. Phase transition temperatures determined from temperature variation of Dielectric Constant (or relative permittivity εr (T)) agree with TM and DSC. Dielectric dispersion reveals different re−orientation processes viz., a slow (LF∼1 kHZ) and a fast (HF∼1 MHz) one in both the B2 and B5 phases. Both the relaxations in B5(AF) phase follow Arrhenius shift to infer 1.12 and 0.89 eV of activation energies, respectively. Off-centred dispersion studied through the Cole-Cole plots in B5(AF) phase infer the increasing trend of dielectric increment �ε and distribution parameterα with decreasing temperature. Trends of �ε and α-parameter suggest a greater fall of response width during slow reorientation and a relative freezing rate during fast reorientation.

Item Type: Article
Additional Information: Copyright © Taylor & Francis Group, LLC
Uncontrolled Keywords: Bent liquid crystal; achiral; ferro; antiferroelectric; spontaneous polarization; relaxations; scissor-mode; activation energy
Subjects: Engineering > MIT Manipal > Chemistry
Depositing User: MIT Library
Date Deposited: 09 Feb 2013 05:30
Last Modified: 09 Feb 2013 05:30
URI: http://eprints.manipal.edu/id/eprint/78308

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