Field-induced transformations in the biaxial order of non-tilted phases in a bent-core smectic liquid crystal

Panarin, Yu. P.; Nagaraj, Mamatha; Vij, J. K.; Keith, Christina; Tschierske, Carsten

doi:10.1209/0295-5075/92/26002

Cited by 34 publications

(30 citation statements)

References 21 publications

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“…The biaxiality in orthogonal smectics can be exploited to produce fast electro-optic devices since it has already been established that LCs are excellently aligned in these phases [15,16]. The anisotropic properties of LCs can be characterized by the molecular polarizability tensor χ M n,ij which can be diagonalized in the molecular frame as χ…”

Section: Theorymentioning

confidence: 99%

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Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals

Sreenilayam¹,

Panarin

Vij

et al. 2013

Phys. Rev. E

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This version is available at https://strathprints.strath.ac.uk/47177/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output.PHYSICAL REVIEW E 88, 012504 (2013) Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals The fundamental parameter of the uniaxial liquid crystalline state that governs nearly all of its physical properties is the primary orientational order parameter (S) for the long axes of molecules with respect to the director. The biaxial liquid crystals (LCs) possess biaxial order parameters depending on the phase symmetry of the system. In this paper we show that in the first approximation a biaxial orthogonal smectic phase can be described by two primary order parameters: S for the long axes and C for the ordering of the short axes of molecules. The temperature dependencies of S and C are obtained by the Haller's extrapolation technique through measurements of the optical birefringence and biaxiality on a nontilted polar antiferroelectric (Sm-AP A ) phase of a homologous series of LCs built from the bent-core achiral molecules. For such a biaxial smectic phase both S and C, particularly the temperature dependency of the latter, are being experimentally determined. Results show that S in the orthogonal smectic phase composed of bent cores is higher than in Sm-A calamatic LCs and C is also significantly large.

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Section: Theorymentioning

confidence: 99%

“…In the Sm-AP A phase, polar directions in the neighboring layers are antiparallel leading to the biaxial antiferroelectric phase. An application of the in-plane electric field higher than its threshold value in the Sm-AP A phase causes a field-induced transition to the ferroelectric Sm-AP F state [15,16].…”

Section: Introductionmentioning

confidence: 99%

Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals

Sreenilayam¹,

Panarin

Vij

et al. 2013

Phys. Rev. E

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“…The first experimental evidence for the existence of a SmAP phase in bent-core liquid crystals was given by Eremin et.al [12] The compound exhibited a biaxial antiferroelectric polar smectic A (SmAPA) phase with the polarization of alternating neighbouring layers being antiparallel [ Fig.1]. A number of novel electro-optic effects in the SmAPA phase were reported by Nagaraj et al [13] where the reorientations in the SmAPA phase exhibit biaxial-uniaxial-biaxial transitions, with switching times of the order of ~500 µsec [13][14]. The SmAPR phase, a lamellar structure that has random arrangement of the in-layer polarization, was discovered by Pociecha et al in 2003.…”

Section: Orthogonal Polar Smectic Phasesmentioning

confidence: 99%

Dark conglomerate phases of bent-core liquid crystals

Nagaraj

2016

Liquid Crystals

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Spontaneous or induced chiral symmetry breaking in achiral systems is unusual and understanding the origin of such a phenomenon has been an important area of research for several years. The optically isotropic mesophases exhibited by unconventional liquid crystals are one of the most interesting systems to investigate spontaneous chiral symmetry breaking in liquid crystal mesophases formed by achiral moieties. The dark conglomerate (DC) phases are one such optically isotropic family of phases. In this paper, a detailed account of the tendency of bent-core mesogens to form a variety of polar smectic phases, the formation of DC phases due to layers deformations and the general optical, electrical, physical properties of the DC phases are given. An example of a dark conglomerate phase which exhibit distinct electro-optic properties is described with the nature of dynamics of the response and physical reasons responsible for such behaviour. The challenges and prospects of the dark conglomerate phases are discussed for their potential applications in novel devices.

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“…12 A detailed work on electric field induced textural transformations in SmAP A phase of this sample are given elsewhere. 13 The material shows negative dielectric anisotropy through out the liquid crystalline temperature range. Polymer AL60702 ͑JSR Korea͒ is used as an alignment agent for the homeotropic cells.…”

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confidence: 99%

“…In the very narrow range of intermediate E, the homeotropic cell appears dark under crossed polarizers arising from zero biaxiality; this is possible when the angle between the local polarizations vectors ͑and therefore the polar directors͒ is 90°. 13 This sequence of transition of the biaxiality is exploited in driving the display either between the low E bright state ͑1͒ to an intermediate E dark state ͑2͒ ͓mode 2͑a͔͒ or between the states ͑2͒ to a high E bright state ͑3͒ ͓mode 2͑b͔͒. The former type of switching could be achieved at very low fields but switching time is rather large compared to the latter type of switching where we need to apply relatively moderate fields for faster switching.…”

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confidence: 99%

Liquid crystal display modes in a nontilted bent-core biaxial smectic liquid crystal

Nagaraj

Panarin

Vij

et al. 2010

Applied Physics Letters

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Liquid crystal display (LCD) modes associated with the rotation of the secondary director in nontilted, biaxial smectic phase of an achiral bent-core compound are demonstrated. For LCDs, we find that at least four display modes are possible using SmAPA phase of the studied material, in which the minor directors in adjacent layers are aligned antiferroelectrically. The advantages of these modes include low driving field (1–2 V/μm), high contrast ratio 1000:1, relatively fast switching time of 0.5 ms and continuous gray scale. The molecular short axis or the polar axis in a negative dielectric, biaxial material is oriented by the in-plane electric field by a combination dielectric biaxiality and polarity at low electric fields and polarity at higher fields.

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Field-induced transformations in the biaxial order of non-tilted phases in a bent-core smectic liquid crystal

Cited by 34 publications

References 21 publications

Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals

Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals

Dark conglomerate phases of bent-core liquid crystals

Liquid crystal display modes in a nontilted bent-core biaxial smectic liquid crystal

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