1
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Iakoubovskii K, Yoshio M. Highly luminescent and photoconductive columnar liquid crystals with a thiophene-oxadiazole backbone. Chem Commun (Camb) 2023. [PMID: 37254595 DOI: 10.1039/d3cc01797d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report columnar liquid-crystalline thiophene-oxadiazole molecules, which can be oriented by electric field and exhibit photodiode properties with an open-circuit voltage of 1 V. Their yellow luminescence can be excited by UV-visible or infrared light. Their room-temperature phosphorescence turns brighter upon heating.
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Affiliation(s)
- Konstantin Iakoubovskii
- Research Center for Macromolecules & Biomaterials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
| | - Masafumi Yoshio
- Research Center for Macromolecules & Biomaterials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
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2
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Patranabish S, Sinha A, Kanakala MB, Yelamaggad CV. Nematic twist-bend phase of a bent liquid crystal dimer: field-induced deformations of the helical structure and macroscopic polarization. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:465101. [PMID: 36067787 DOI: 10.1088/1361-648x/ac8fd3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 09/06/2022] [Indexed: 06/15/2023]
Abstract
The twist-bend nematic (Ntb) phase is a recent addition to the family of nematic (N) phases of liquid crystals (LCs). A net polar order in the Ntbphase under an external electric field is interesting and it was predicted in several recent theoretical studies. We investigated the field-induced polarization behaviour, dielectric, and electro-optic properties of a bent LC dimer CB7CB in the N and Ntbphases. A threshold-dependent polarization current response was obtained in both the phases under triangular and square-wave input electric fields, existing till frequencies as high as 150 Hz. The polarization switching times were found in ∼1 ms region, especially in the N phase. In the Ntbphase, electric field-induced deformation of the helical structure was observed, like ferroelectric LCs. Dielectric measurements revealed the presence of cybotactic clusters via collective relaxations. The dielectric anisotropy (Δϵ) is negative at the frequencies of polarization measurements. The net polarization resulted from field-induced reorientation of cybotactic clusters and additionally from the field-induced deformation of helical structures in the Ntbphase. We explored the possibility of ionic contributions to the net polarization by synthesizing TiO2nanoparticles (NPs) dispersed CB7CB LC nanocomposite. Incorporation of the NPs resulted in reduction of the collective order, increase in the ionic impurity content and conductivity, but an extinction of the field-induced polarization response. Our results demonstrate that the net polarization has competing contributions from both ferroelectric-like and ionic origin (up to ∼10 Hz) in the LC phases, but it becomes dominantly ferroelectric-like at higher frequencies.
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Affiliation(s)
- Sourav Patranabish
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Aloka Sinha
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Madhu B Kanakala
- Centre for Nano and Soft Matter Sciences, Survey No. 7, Shivanapura, Dasanapura Hobli, Bengaluru 562162, India
| | - C V Yelamaggad
- Centre for Nano and Soft Matter Sciences, Survey No. 7, Shivanapura, Dasanapura Hobli, Bengaluru 562162, India
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3
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Electric-field-induced patterns in a hockey-stick nematic. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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4
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Ali GQ, Tomi IHR. Non-symmetrical bent-core homologous series bearing 1,2,4-oxadiazole core with a cholesterol terminal arm: Synthesis, characterization and their liquid crystalline properties. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.132610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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5
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Shanker G, Srinatha M, Sandhya Kumari D, Ranjitha B, Alaasar M. Novel green synthetic approach for liquid crystalline materials using multi-component reactions. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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6
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Pristine and ferroelectric liquid crystal dispersed four ring bent core nematic: Impact of dispersion on electro-optic and dielectric properties. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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7
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Patranabish S, Wang Y, Sinha A, Majumdar A. Quantum-dots-dispersed bent-core nematic liquid crystal and cybotactic clusters: Experimental and theoretical insights. Phys Rev E 2021; 103:052703. [PMID: 34134338 DOI: 10.1103/physreve.103.052703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 04/09/2021] [Indexed: 11/07/2022]
Abstract
We study a quantum-dots (QDs) dispersed bent-core nematic liquid crystalline system in planar geometry and present experimental measurements of the birefringence (Δn), order parameter (S), dielectric dispersion, absorption spectra, and optical textures with attention to variations with temperature. A bent-core liquid crystal (LC) 14-2M-CH_{3} is used as the host material and CdSe/ZnS core-shell type QDs are used as the dopant. The nematic (N) phase of the pristine (undoped) LC 14-2M-CH_{3} contains cybotactic clusters, which are retained by its QDs incorporated LC nanocomposite. Our experimental findings support: (i) reduced orientational order parameter of the QDs dispersed LC system compared to its pristine counterpart at fixed temperatures, (ii) reduced cybotactic cluster sizes due to the incorporation of QDs, and (iii) increased activation energies related to reduced cluster sizes. We complement the experiments with a novel Landau-de Gennes-type free energy for a doped bent-core LC system that qualitatively captures the doping-induced reduced order parameter and its dependence on the properties of the QDs and its variation with temperature.
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Affiliation(s)
- Sourav Patranabish
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Yiwei Wang
- Department of Applied Mathematics, Illinois Institute of Technology, Chicago, Illinois 60616, USA
| | - Aloka Sinha
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Apala Majumdar
- Department of Mathematics and Statistics, University of Strathclyde, Glasgow G11XQ, United Kingdom
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8
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2,3,4-Trihydroxy benzonitrile-based liquid crystals: Fiber forming room temperature nematic phases. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114244] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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9
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Vita F, Adamo FC, Pisani M, Francescangeli O. Nanostructure of Unconventional Liquid Crystals Investigated by Synchrotron Radiation. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1679. [PMID: 32859117 PMCID: PMC7558469 DOI: 10.3390/nano10091679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 07/27/2020] [Accepted: 08/12/2020] [Indexed: 11/30/2022]
Abstract
The macroscopic properties of novel liquid crystal (LC) systems-LCs with unconventional molecular structure as well as conventional LCs in unconventional geometries-directly descend from their mesoscopic structural organization. While X-ray diffraction (XRD) is an obvious choice to investigate their nanoscale structure, conventional diffractometry is often hampered by experimental difficulties: the low scattering power and short-range positional order of the materials, resulting in weak and diffuse diffraction features; the need to perform measurements in challenging conditions, e.g., under magnetic and/or electric fields, on thin films, or at high temperatures; and the necessity to probe micron-sized volumes to tell the local structural properties from their macroscopic average. Synchrotron XRD allows these problems to be circumvented thanks to the superior diffraction capabilities (brilliance, q-range, energy and space resolution) and advanced sample environment available at synchrotron beamlines. Here, we highlight the potentiality of synchrotron XRD in the field of LCs by reviewing a selection of experiments on three unconventional LC systems: the potentially biaxial and polar nematic phase of bent-core mesogens; the very high-temperature nematic phase of all-aromatic LCs; and polymer-dispersed liquid crystals. In all these cases, synchrotron XRD unveils subtle nanostructural features that are reflected into macroscopic properties of great interest from both fundamental and technological points of view.
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Affiliation(s)
| | | | | | - Oriano Francescangeli
- Dipartimento di Scienze e Ingegneria della Materia, dell’Ambiente ed Urbanistica, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy; (F.V.); (F.C.A.); (M.P.)
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10
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Abdulnabi NM, Habeeb HQA, Tomi IHR, Jaffer HJ. Synthesis and Characterization of Some Boomerang Imine‐Ester Mesogenic Materials Based on Thiophene Unit. ChemistrySelect 2020. [DOI: 10.1002/slct.202001857] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Nabih M. Abdulnabi
- Department of Chemistry, College of ScienceMustansiriyah University Baghdad Iraq
| | | | - Ivan H. R. Tomi
- Department of Chemistry, College of ScienceMustansiriyah University Baghdad Iraq
| | - Hamed J. Jaffer
- Department of Chemistry, College of ScienceMustansiriyah University Baghdad Iraq
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11
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Kaur S, Mohiuddin G, Punjani V, Khan RK, Ghosh S, Pal SK. Structural organization and molecular self-assembly of a new class of polar and non-polar four-ring based bent-core molecules. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111687] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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12
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Saha S, Mohiuddin G, Paul MK, Gupta SP, Khan RK, Ghosh S, Pal SK. Polar Switching and Cybotactic Nematic Ordering in 1,3,4-Thiadiazole-Based Short-Core Hockey Stick-Shaped Fluorescent Liquid Crystals. ACS OMEGA 2019; 4:7711-7722. [PMID: 31459861 PMCID: PMC6648508 DOI: 10.1021/acsomega.9b00425] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 03/27/2019] [Indexed: 06/10/2023]
Abstract
We report here the synthesis and thermotropic properties of novel short-core hockey stick-shaped liquid crystalline molecules based on the 1,3,4-thiadiazole core. Polar switching behavior is observed in the cybotactic nematic and smectic mesophases for the bent-core thiadiazole derivatives. The presence of the lateral methoxy moiety in the outer phenyl ring of the four-ring molecules facilitates the formation of spontaneous ordering in the nematic phase observed via X-ray diffraction measurements. Anomalous temperature dependence of spontaneous polarization on cooling is explained by the possible antiferroelectric packing of the molecules that require higher electric field for switching. The compounds exhibited a strong absorption band at ∼356 nm and a blue emission band at ∼445 nm with a good quantum yield of φf ∼0.39. The mega Stokes shift is observed and depends on the nature of the solvent.
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Affiliation(s)
- Sandip
Kumar Saha
- Department
of Chemistry, Assam University, Silchar, Assam 788011, India
| | - Golam Mohiuddin
- Department
of Chemical Sciences, Indian Institute of
Science Education and Research (IISER) Mohali, Sector-81, Knowledge City, Manauli, 140306, India
| | - Manoj Kumar Paul
- Department
of Chemistry, Assam University, Silchar, Assam 788011, India
| | | | - Raj Kumar Khan
- Department
of Physics, University of Calcutta, 92 Acharyya Prafulla Chandra Road, Calcutta University, Kolkata 700009, India
| | - Sharmistha Ghosh
- Department
of Physics, University of Calcutta, 92 Acharyya Prafulla Chandra Road, Calcutta University, Kolkata 700009, India
| | - Santanu Kumar Pal
- Department
of Chemical Sciences, Indian Institute of
Science Education and Research (IISER) Mohali, Sector-81, Knowledge City, Manauli, 140306, India
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13
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Patranabish S, Wang Y, Sinha A, Majumdar A. One-dimensional theoretical analysis of coupling and confinement effects on the cybotactic clusters of bent-core nematic liquid crystals. Phys Rev E 2019; 99:012703. [PMID: 30780335 DOI: 10.1103/physreve.99.012703] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Indexed: 11/07/2022]
Abstract
The bent-core liquid crystals (LCs) are highly regarded as the next-generation materials for electro-optic devices. The nematic (N) phase of these LCs possesses highly ordered smecticlike cybotactic clusters which are promising for electro-optic applications. We have studied a one-dimensional Landau-de Gennes model of spatially inhomogeneous order parameters for the N phase of bent-core LCs. We investigate the effects of spatial confinement and coupling (between these clusters and the surrounding LC molecules modeled by a coupling parameter γ) on the order parameters. The coupling is found to increase the cluster order parameter significantly, suggesting enhancement in cluster formation, and also predicts a transition to a phase with weak nematiclike ordering above the nematic supercooling temperature.
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Affiliation(s)
- Sourav Patranabish
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Yiwei Wang
- School of Mathematical Sciences, Peking University, Beijing 100871, China
| | - Aloka Sinha
- Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Apala Majumdar
- Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, England, United Kingdom
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14
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Nafees A, Kalita G, Sinha A. Effect of titanium dioxide nanoparticles on the dielectric and electro-optical properties of bent-core liquid crystals. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2018.11.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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16
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Merkel K, Kocot A, Vij JK, Shanker G. Distortions in structures of the twist bend nematic phase of a bent-core liquid crystal by the electric field. Phys Rev E 2018; 98:022704. [PMID: 30253534 DOI: 10.1103/physreve.98.022704] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Indexed: 05/16/2023]
Abstract
The dielectric spectra of the twist bend nematic phase (N_{TB}) of an achiral asymmetric bent-core liquid crystalline compound are studied for determining the various relaxation modes. Dielectric measurements are also carried out under the bias field E up to 8 V/µm. Two molecular and two collective relaxation processes are observed. The orientational order parameters with respect to the local and the main directors determined using molecular modes are used to find the heliconical angle. The results also show that the order parameter with reference to the main director reverses its trend from increasing to decreasing at temperatures of a few degrees above the N_{TB} to N transition. The collective relaxation modes are assigned to (a) distortions of the local director by the electric field at a frequency of ∼100kHz while the periodic helical structure remains unaltered (mode attributed to flexoelectricity); (b) changes in the periodic structure arising from a coupling of the dielectric anisotropy with the electric field at the lowest frequency in the range of 100 Hz-10 kHz. Frequency of the higher frequency collective mode (∼100kHz) depends primarily on the heliconical angle and has anomalous softeninglike behavior at the N-N_{TB} transition. The lowest frequency mode is studied under the bias field E; the modulus of the wave vector gradually vanishes on increasing E (except for an initial behavior, E^{2}<0.1V^{2}/μm^{2}, which is just the opposite). The transition from the twist bend to splay bend structure is observed by a sudden drop in the frequency of this mode, followed by a linear decrease in frequency by increasing E. The results agree with the predictions made from the currently proposed models for a periodically distorted N_{TB} phase.
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Affiliation(s)
- K Merkel
- Institute of Material Science, Silesian University, Katowice 40-007, Poland
| | - A Kocot
- Institute of Material Science, Silesian University, Katowice 40-007, Poland
| | - J K Vij
- Department of Electronic and Electrical Engineering, School of Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - G Shanker
- Department of Studies in Chemistry, Jnana Bharathi Campus, Sneha Bhavan, Bangalore University, Bangalore 560056, India
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17
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Cybotactic nematic phase of achiral unsymmetrical bent-core liquid crystals – Quelling of polar ordering and the influence of terminal substituent moiety. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.02.097] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Kumar J, Prasad V. Ferroelectric Nematic and Ferrielectric Smectic Mesophases in an Achiral Bent-Core Azo Compound. J Phys Chem B 2018; 122:2998-3007. [PMID: 29485879 DOI: 10.1021/acs.jpcb.7b11733] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here, we report the observation of ferroelectric nematic and ferrielectric smectic mesophases in an achiral bent-core azo compound consisting of nonsymmetrical molecules with a lateral fluoro substitution on one of the wings. These mesophases are enantiotropic in nature with fairly low transition temperatures and wide mesophase ranges. The liquid crystalline properties of this compound are investigated using polarizing optical microscope, differential scanning calorimeter, X-ray diffraction, and electro-optical studies. As revealed by X-ray diffraction measurements, the nematic mesophase is composed of skewed cybotactic clusters and, in the smectic mesophase, the molecules are tilted with respect to the layer normal. The polar order in these mesophases was confirmed by the electro-optical switching and dielectric spectroscopy measurements. The dielectric study in the nematic mesophase shows a single relaxation process at low frequency ( f < 1 kHz) measured in the range 10 Hz to 5 MHz, which is attributed to the collective motion of the molecules within cybotactic clusters. The formation of local polar order in these clusters leads to a ferroelectric-like polar switching in the nematic mesophase. Of particular interest is the fact that the smectic phase exhibits a field induced ferrielectric state, which can be exploited for designing of the potential optical devices due to multistate switching.
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Affiliation(s)
- Jitendra Kumar
- Centre for Nano and Soft Matter Sciences , P.B. No. 1329, Jalahalli, Bengaluru - 560 013 , India
| | - Veena Prasad
- Centre for Nano and Soft Matter Sciences , P.B. No. 1329, Jalahalli, Bengaluru - 560 013 , India
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19
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Kumar P, Debnath S, Rao NVS, Sinha A. Nanodoping: a route for enhancing electro-optic performance of bent core nematic system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:095101. [PMID: 29336349 DOI: 10.1088/1361-648x/aaa801] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report the effect of dispersion of barium titanate (BaTiO3) nanoparticles (BNPs) in a four ring bent core nematic (BCN) liquid crystal. Polarizing optical microscopy reveals the presence of a single nematic phase in pure and doped states. Polar switching has been observed in the bent core system and the value of spontaneous polarization (P s) increases with increase in doping concentration of BNPs in BCN. Dielectric study shows a lower frequency mode, which can be ascribed to the formation of cybotactic clusters. These clusters are also responsible for the observed polar switching in pure, as well as, in doped BCNs. Another higher frequency mode, observed only in pure BCN, indicates the rotation of molecules about their long molecular axis. The conductivity of doped samples is also found to decrease as compared to the pure BCN. This reduction helps in the minimization of negative effects caused by free ions in liquid crystal based devices. This study demonstrates that the interaction between BNPs and BCN molecules improves the P s, dielectric behaviour, viscosity and reduces the conductivity of pure BCN. Hence, nanodoping in a BCN is an effective method for the enhancement of electro-optic performances and will lead to the development of faster electro-optic devices.
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Affiliation(s)
- Pradeep Kumar
- Department of Physics, Indian Institute of Technology Delhi, 110016, India
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20
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Santhosh Kumar Reddy Y, Lobo NP, Narasimhaswamy T. Effect of alkyl chain and linking units on mesophase transitions and molecular order of rod-like thiophene mesogens:13C NMR investigation. NEW J CHEM 2018. [DOI: 10.1039/c7nj03525j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
This study provides insight into the influence of alkyl chains and linking units on the mesophase properties of thiophene-based mesogens and on the orientational constraints of the core and terminal alkyl chain.
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Affiliation(s)
| | - Nitin P. Lobo
- Inorganic & Physical Chemistry
- CSIR-Central Leather Research Institute
- Chennai 600020
- India
| | - T. Narasimhaswamy
- Polymer Science & Technology
- CSIR-Central Leather Research Institute
- Chennai 600020
- India
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21
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Torgova S, Sreenilayam SP, Panarin YP, Francescangeli O, Vita F, Vij JK, Pozhidaev E, Minchenko M, Ferrero C, Strigazzi A. Short bent-core molecules: X-ray, polarization, dielectricity, texture and electro-optics investigations. Phys Chem Chem Phys 2017; 19:22946-22956. [PMID: 28813044 DOI: 10.1039/c7cp03561f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Bent-core liquid crystals based on 1,2,4-oxadiazole as a central unit have been the first mesogens to exhibit a ferroelectric response in the nematic phase. This behavior has been widely recognized as due to the presence of smectic-like polar cybotactic clusters permeating the nematic phase. Unfortunately, these compounds exhibited rather high melting points, about 120 °C, due to the presence of four benzene rings in the molecules. Here we describe the synthesis and physical characterization of a new series of BC mesogens, featuring the same bent core as the previous compounds but shorter outer substituents. By keeping only two benzene rings, we were able to lower the melting points to about 70 °C. However, while X-ray diffraction and dielectric spectroscopy measurements confirm the cybotactic nature of the nematic phase of these compounds, polarization and electro-optical measurements ascribe their polar response to flexoelectricity rather than to spontaneous polarization. Finally, texture investigation suggests the biaxiality of the nematic phase, which is indicated also by conoscopic measurements. These results are important for recognizing size and rigidity limitations in designing bent-core liquid crystal molecules suitable for applications.
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Affiliation(s)
- S Torgova
- P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Pr. 53, Moscow, 119991, Russia
| | - S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland
| | - Yu P Panarin
- Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland and School of Electrical and Electronic Engineering, Dublin Institute of Technology, Dublin, Ireland
| | - O Francescangeli
- Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio and CNISM, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - F Vita
- Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio and CNISM, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland
| | - E Pozhidaev
- P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Pr. 53, Moscow, 119991, Russia
| | - M Minchenko
- P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Pr. 53, Moscow, 119991, Russia
| | - C Ferrero
- European Synchrotron Radiation Facility, Bôite Postale 220, 38043 Grenoble Cedex, France
| | - A Strigazzi
- Department of Applied Science and Technology, Physics Institute of Condensed Matter and Complex Systems, CNISM, Politecnico di Torino, Torino, Italy. and National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia
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22
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Asymmetric 1,3,4-thiadiazole derivatives: Synthesis, characterization and studying their liquid crystalline properties. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2017.03.105] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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23
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Pradhan B, Chakraborty N, Gupta RK, Shanker G, Achalkumar AS. Nonsymmetrical cholesterol dimers constituting regioisomeric oxadiazole and thiadiazole cores: an investigation of the structure–property correlation. NEW J CHEM 2017. [DOI: 10.1039/c6nj03141b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effect of a bent angle on the stabilization of liquid crystalline and organogel self-assemblies.
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Affiliation(s)
- Balaram Pradhan
- Department of Chemistry
- Indian Institute of Technology Guwahati
- India
| | | | | | - G. Shanker
- Department of Studies in Chemistry
- Bangalore University
- Bangalore
- India
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24
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Kaur S, Punjani V, Mohiuddin G, Pal SK. Orthogonal smectic and nematic ordering in three-ring polar bent-core molecules with anti-parallel arrangement. NEW J CHEM 2017. [DOI: 10.1039/c7nj00272f] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Three-ring based BLCs exhibiting orthogonal smectic and nematic phases with antiparallel arrangement as derived from SCXRD and X-ray scattering results.
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Affiliation(s)
- Supreet Kaur
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Vidhika Punjani
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Golam Mohiuddin
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Santanu Kumar Pal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
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25
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Pathak SK, Nath S, De J, Pal SK, Achalkumar AS. The effect of regioisomerism on the mesomorphic and photophysical behavior of oxadiazole-based tris(N-salicylideneaniline)s: synthesis and characterization. NEW J CHEM 2017. [DOI: 10.1039/c7nj01766a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two new regioisomeric star-shaped tris(N-salicylideneaniline)s are synthesized and characterized.
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Affiliation(s)
- Suraj Kumar Pathak
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati
- India
| | - Subrata Nath
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati
- India
| | - Joydip De
- Department of Chemical Sciences
- Indian Institute of Science Education and Research Mohali
- Manauli 140306
- India
| | - Santanu Kumar Pal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research Mohali
- Manauli 140306
- India
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26
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Effect of Atomic-Scale Differences on the Self-Assembly of Thiophene-based Polycatenars in Liquid Crystalline and Organogel States. Chemistry 2016; 22:17843-17856. [DOI: 10.1002/chem.201603678] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/02/2016] [Indexed: 11/07/2022]
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27
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Pathak SK, Gupta M, Pal SK, Achalkumar AS. Hexacatenars Exhibiting π-π Driven Supergelation, Aggregation Induced Blue Light Emission and Thermochromism. ChemistrySelect 2016. [DOI: 10.1002/slct.201600927] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Suraj K. Pathak
- Department of Chemistry; Indian Institute of Technology Guwahati; Guwahati 781039, Assam India
| | - Monika Gupta
- Department of Chemical Sciences; Indian Institute of Science Education and Research (IISER) Mohali, Sector-81, Knowledge City; Manauli 140306, Punjab India
| | - Santanu K. Pal
- Department of Chemical Sciences; Indian Institute of Science Education and Research (IISER) Mohali, Sector-81, Knowledge City; Manauli 140306, Punjab India
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28
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Nafees A, Sinha A, Rao NVS, Kalita G, Mohiuddin G, Paul MK. Design, synthesis and mesomorphic behaviour of a four-ring achiral bent-core liquid crystal in the nematic phase. RSC Adv 2016. [DOI: 10.1039/c6ra05125a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Design, synthesis and characterization of a four-ring achiral bent-core liquid crystal with a broad range nematic phase which can be cooled down without crystallization.
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Affiliation(s)
- Amina Nafees
- Department of Physics
- Indian Institute of Technology Delhi
- New Delhi-110016
- India
| | - Aloka Sinha
- Department of Physics
- Indian Institute of Technology Delhi
- New Delhi-110016
- India
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29
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Sreenilayam SP, Panarin YP, Vij JK, Torgova SI, Lehmann A, Tschierske C. Flexoelectric polarization studies in bent-core nematic liquid crystals. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:022502. [PMID: 26382418 DOI: 10.1103/physreve.92.022502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Indexed: 06/05/2023]
Abstract
The flexoelectric polarization (Pf) of four bent-core nematic liquid crystals (LCs) has been measured using the pyroelectric effect. Hybrid aligned nematic cells are fabricated for measuring the pyroelectric response over the entire range of the nematic phase. It is found that the magnitude of flexoelectric polarization Pf and the sum of the flexoelectric coefficients |e1+e3| for the bent-core LCs studied here are three to six times higher than for the calamitics. Pf is found to depend on the transverse dipole moment of LC molecules. However, |e1+e3| values are by no means giant as |e3| alone had been reported for a bent-core nematic system previously. The dependence of the sum of "splay and bend flexoelectric coefficients" is discussed in terms of the shape of the molecule and of the dipole moment directed normal to the molecular axis.
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Affiliation(s)
- S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
| | - Yu P Panarin
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
- School of Electrical and Electronic Engineering, Dublin Institute of Technology, Dublin 8, Ireland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
| | - S I Torgova
- P. N. Lebedev Physical Institute of Russian Academy of Sciences, Moscow, Russia
| | - A Lehmann
- Institute of Chemistry, Martin-Luther-University, Halle-Wittenberg, 06120 Halle, Germany
| | - C Tschierske
- Institute of Chemistry, Martin-Luther-University, Halle-Wittenberg, 06120 Halle, Germany
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30
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Liu N, Zhai LJ, Lian P, Li H, Wang BZ. Synthesis of 3,5,5-Trisubstituted 4-Hydroxy-4 H,5 H-1,2,4-oxadiazoles through the Condensation of N-Hydroxyamidoximes and Ketones or Aldehydes. European J Org Chem 2015. [DOI: 10.1002/ejoc.201500083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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Pace A, Buscemi S, Piccionello AP, Pibiri I. Recent Advances in the Chemistry of 1,2,4-OxadiazolesaaDedicated to Professor Nicolò Vivona on the occasion of his 75th birthday. ADVANCES IN HETEROCYCLIC CHEMISTRY 2015. [DOI: 10.1016/bs.aihch.2015.05.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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