B. K. Sadashiva

Raman Research Institute

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R. Amaranatha Reddy

University of Colorado Boulder

R. Pratibha

Raman Research Institute

Radhika Srinivasan

Post Graduate Institute of Medical Education and Research

Surajit Dhara

University of Hyderabad

H. N. Shreenivasa Murthy

Martin Luther University Halle-Wittenberg

S. Chandrasekhar

Indian Institute of Science Bangalore

S. Umadevi

Alagappa University

N. V. Madhusudana

Raman Research Institute

V. A. Raghunathan

Raman Research Institute

Antal Jákli

Kent State University

Cooperative Institutions

Raman Research Institute

Kent State University

Tokyo Institute of Technology

Centre National de la Recherche Scientifique

Indian Institute of Science Bangalore

Bangalore University

Crystal Research (United States)

Indian Institute of Technology Madras

Centre for Nano and Soft Matter Sciences

University of Hyderabad

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Synthesis and mesomorphic properties of banana-shaped compounds derived from 2,7-dihydroxynaphthalene

Liquid Crystals (2000)

R. Amaranatha Reddy B. K. Sadashiva

Thirty eight compounds composed of achiral banana-shaped molecules belonging to three new homologous series have been synthesized and their mesomorphic properties investigated. The mesophases have been characterized using a combination of polarized light microscopy, differential scanning calorimetry, miscibility methods and X-ray diffraction measurements. All the compounds reported exhibit mesomorphic properties. Most of the homologues in the three series show B1 and B2 phases and the transition temperatures of these are lower in the fluoro substituted compounds. Some of the lower homologues of the fluoro substituted derivatives also show the nematic phase.

Miscibility

Homologous series

Polarized light microscopy

10.1080/026782900750037176

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Citations (62)

Alternating twist structures formed by electroconvection in the nematic phase of an achiral bent-core molecule

Physical Review E (2008)

Shingo Tanaka Surajit Dhara B. K. Sadashiva Yoshio Shimbo Yoichi Takanishi

We report an unusual electroconvection in the nematic phase of a bent-core liquid crystal. In a voltage-frequency diagram, two frequency regions exhibiting prewavy stripe patterns were found, as reported by Wiant We found that these stripes never show extinction dark when cells were rotated under crossed polarizers. Based on the color interchange in between neighboring stripes by the rotation of the cells or an analyzer, twisted molecular orientation is suggested; i.e., the directors are alternately twisted from the top to the bottom surfaces with a pretilt angle in adjacent stripes, which is an analogue of the twisted (splayed) structure observed in surface-stabilized ferroelectric liquid crystal cells. The transmittance spectra calculated using the 4x4 matrix method from the model structure are consistent with the experimental observation.

Polarizer

10.1103/physreve.77.041708

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Citations (36)

The SmCP_Aphase in five‐ring bent‐core compounds derived from 5‐methoxyisophthalic acid

Liquid Crystals (2006)

S. Umadevi Radhika Srinivasan B. K. Sadashiva

The synthesis and mesophase characterization of a homologous series of five‐ring bent‐core compounds derived from 5‐methoxyisophthalic acid are described. Most of the compounds exhibit a polar antiferroelectric smectic C phase. Replacement of the terminal n‐alkoxy chains by n‐alkyl carboxylate groups, not only destabilizes the formation of mesophases but induces a calamitic mesophase. However, extension of the arms of the bent‐core molecule by a phenyl moiety stabilizes the switchable phase. The mesophases were investigated using a combination of polarizing optical microscopy, differential scanning calorimetry, X‐ray diffraction and electro‐optical methods.

Moiety

Homologous series

10.1080/02678290500473586

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Citations (16)

Novel zigzag-shaped compounds exhibiting apolar columnar mesophases with oblique and rectangular lattices

Liquid Crystals (2013)

Radhika Srinivasan M. Monika B. K. Sadashiva Amritendu Roy

The design, synthesis and characterisation of some compounds whose constituent molecules have a completely new shape have been carried out. A total of eight different series/part of series of these zigzag-shaped compounds that are either symmetrical or unsymmetrical were synthesised. Only two mesophases were observed, and on the basis of polarising optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies, these have been characterised as columnar phases with a rectangular or an oblique lattice. Perhaps, these represent the first examples of a rigid zigzag-shaped compound exhibiting a mesophase.

Zigzag

10.1080/02678292.2013.806680

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Citations (11)

Observation of filamentary growth patterns at the isotropic–SmCP_Aphase transition in new unsymmetrical compounds composed of bent-core molecules

Liquid Crystals (2004)

H. N. Shreenivasa Murthy B. K. Sadashiva

Abstract The synthesis and mesomorphic properties of several compounds composed of bent-core molecules, unsymmetrically substituted about the central phenyl ring, are discussed. These compounds contain substituents such as fluoro, chloro and trifluoromethyl at the terminal position of one of the arms of the bent-core molecules. Many of the compounds containing a chloro terminal substituent show filamentary growth patterns at the transition from isotropic to polar antiferroelectric smectic C phase. The liquid crystalline phase exhibited by these compounds has been characterized using a combination of polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies.

Antiferroelectricity

Polarized light microscopy

10.1080/02678290310001655249

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Citations (15)

Observation of a transition from non-switchable B7 mesophase to an antiferroelectric sub-phase in strongly polar bent-core compoundsElectronic supplementary information (ESI) available: data for compounds 7, 8 and 9 as well as the general synthetic procedure for the preparation of the compounds of series II. See http://www.rsc.org/suppdata/jm/b3/b309138d/

Journal of Materials Chemistry (2003)

H. N. Shreenivasa Murthy B. K. Sadashiva

The synthesis and characterization of two new homologous series of five-ring Schiff's base esters exhibiting the non-switchable B7 mesophase are reported. These compounds have been derived from either 2-nitro- or 2-cyanoresorcinol. Interestingly, three higher homologues of the nitro-substituted compounds undergo a transition from the non-switchable B7 mesophase to an antiferroelectric sub-phase (B7AF1), which is the first example of such a transition. In addition to comparing the mesomorphic behaviour of the two series of compounds, the effect of reversing the azomethine linkage group in these series of compounds has also been examined. The mesophases have been characterized by conventional techniques.

Homologous series

Antiferroelectricity

10.1039/b309138d

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Citations (29)

Kerr constant and third-order nonlinear optic susceptibility measurements in a liquid crystal composed of bent-shaped molecules

Physical Review E (2008)

Surajit Dhara Fumito Araoka Mongryong Lee Khoa V. Le Lingfen Guo

We report the determination of the Kerr constant $(B)$ and the real part of the third-order nonlinear optic susceptibility $({\ensuremath{\chi}}^{(3)})$ above the nematic-isotropic phase transition temperature $({T}_{NI})$ of a liquid crystal composed of bent-shaped molecules. The values of $B$ and ${\ensuremath{\chi}}^{(3)}$ just above $(\ensuremath{\sim}0.3\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ ${T}_{NI}$ are $\ensuremath{\sim}8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕{\mathrm{V}}^{2}$ and $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{2}∕{\mathrm{V}}^{2}$, respectively. The estimated critical temperature ${T}_{C}^{*}$ is about $1.5\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ below ${T}_{NI}$ indicating that the nematic-isotropic $(NI)$ transition is weakly first order as in the case of calamitic liquid crystals. The temperature-dependent Kerr constant is found to be in good agreement with the predictions of the Landau--de Gennes theory. The experimental results are compared with those in a calamitic liquid crystal material with negative dielectric anisotropy in the nematic phase.

Crystal (programming language)

10.1103/physreve.78.050701

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Citations (24)

Banana-shaped mesogens: effect of lateral substituents on seven-ring esters containing a biphenyl moiety

Liquid Crystals (2002)

H. N. Shreenivasa Murthy B. K. Sadashiva

The synthesis and characterization of five homologous series of symmetrical compounds composed of banana-shaped molecules containing a biphenyl moiety are reported. All these compounds are non-Schiff's bases and are esters. The effects of lateral substituents such as fluoro, methyl and ethyl in the side arms of these molecules are examined. These substituents have a strong influence in reducing the clearing temperatures. Banana phases such as B1, B2 and B6 were observed in the above series of compounds. The mesophases were characterized by a combination of polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optic studies.

Moiety

Biphenyl

Homologous series

Side chain

10.1080/02678290210160114

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Citations (74)

Banana-shaped mesogens: observation of a direct transition from the antiferroelectric B2 to nematic phase

Chemical Communications (2001)

R. Amaranatha Reddy B. K. Sadashiva Surajit Dhara

The synthesis and characterisation of the first banana-shaped mesogens which exhibit a direct transition from the antiferroelectric B2 phase to the nematic phase are reported.

Antiferroelectricity

10.1039/b106458b

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Citations (29)

Odd–even effects in bent-core compounds containing terminal n-alkyl carboxylate groups

Soft Matter (2006)

S. Umadevi Antal Jákli B. K. Sadashiva

A homologous series of eleven five-ring symmetrical bent-core compounds containing terminal n-alkyl carboxylate groups were synthesized, characterized and their dielectric and electro-optical properties have been investigated. The lower homologues (n = 6–11) of the series show B2 structures with an interesting odd–even effect concerning their local director tilt and polar arrangements. This odd–even effect probably is due to steric (entropic) reasons, which are not suppressed by the relatively low polar interaction. Three of the middle homologues display a B7′ phase, which is bistable and shows linear electro-optical switching with a transition to the chiral antiferroelectric smectic phase at a lower temperature. The higher homologues (n = 16, 18) exhibit only a B7′ phase.

Homologous series

Antiferroelectricity

Carboxylate

Bistability

10.1039/b605061a

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Citations (24)