Influence of moieties for the phase stability, Spontaneous polarization and Dielectric relaxations in an achiral ferroelectric bent liquid crystal, PBUOB

Chalapathi , P V and Srinivasulu, M and Pisipati, V G K M and Satyanarayana, C H and Potukuchi, D M (2011) Influence of moieties for the phase stability, Spontaneous polarization and Dielectric relaxations in an achiral ferroelectric bent liquid crystal, PBUOB. Physica B, 406 (11). pp. 2081-2090. ISSN 0921-4526

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Abstract

The occurrence of ferroelelectric phases and influence of chemical moieties in the area of supramolecular achiral Bent core Liquid Crystals (BLCs) are reviewed. Synthesis of an intermediate/higher homolog of PBnOB series (for n¼11), PBUOB, viz. 1,3�Phenyline-Bis(4�UndecylOxy Benzoate), is presented. Smectic LC phases exhibited by PBUOB are characterized by Polarized Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and Spontaneous Polarization (PS) techniques. Observations infer a bi-variant FE LC smectic phase occurrence, viz., isotropic-B2(FE)-B5(FE)-solid phases in cooling and solid-B5-isotropic phases in heating scans. Occurrence of B2 phase is monotropic (in cooling), while B5 phase is enantiotropic. I–B2 and B2–B5 phase transitions are found to be of first order nature. The FE phases possess a moderate PS value of �40 nC cm�2. Transition temperatures from dielectric studies agree with those from TM and DSC. Two modes of relaxations are observed, viz., a slow scissor mode at �1 kHz and a fast mode at �1 MHz. Anisotropic Dipolar Model is proposed to explain the reorientation mechanism. Arrhenius shifts of Relaxation Frequency (fR) show differing activation energies for two modes, i.e., 0.11 and 0.98 eV; 0.25 and 1.18 eV in B2 and B5 phases, respectively. Temperature variation of dielectric increment De and a-parameter LC phases reveals the relative fixture of dipole moment in polar smectic layers. An analytical study for the thermal stability, PS and fR in the FE phases is presented with respect to the constitution and configuration of moieties in BLCs.

Item Type: Article
Additional Information: 2011 Elsevier B.V. All rights reserved.
Uncontrolled Keywords: Achiral bent liquid crystals Ferroelectric Textures lorimetry Spontaneous Polatrization Dielectric relaxations Activation energy
Subjects: Engineering > MIT Manipal > Chemistry
Depositing User: MIT Library
Date Deposited: 09 Feb 2013 07:47
Last Modified: 09 Feb 2013 07:47
URI: http://eprints.manipal.edu/id/eprint/78315

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