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Merkel K, Loska B, Arakawa Y, Mehl GH, Karcz J, Kocot A. How Do Intermolecular Interactions Evolve at the Nematic to Twist–Bent Phase Transition? Int J Mol Sci 2022; 23:ijms231911018. [PMID: 36232324 PMCID: PMC9570452 DOI: 10.3390/ijms231911018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/15/2022] [Accepted: 09/18/2022] [Indexed: 11/30/2022] Open
Abstract
Polarized beam infrared (IR) spectroscopy provides valuable information on changes in the orientation of samples in nematic phases, especially on the role of intermolecular interactions in forming the periodically modulated twist–bent phase. Infrared absorbance measurements and quantum chemistry calculations based on the density functional theory (DFT) were performed to investigate the structure and how the molecules interact in the nematic (N) and twist–bend (NTB) phases of thioether dimers. The nematic twist–bend phase observed significant changes in the mean IR absorbance. On cooling, the transition from the N phase to the NTB phase was found to be accompanied by a marked decrease in absorbance for longitudinal dipoles. Then, with further cooling, the absorbance of the transverse dipoles increased, indicating that transverse dipoles became correlated in parallel. To investigate the influence of the closest neighbors, DFT calculations were performed. As a result of the optimization of the molecular cores system, we observed changes in the square of the transition dipoles, which well corresponds to absorbance changes observed in the IR spectra. Interactions of molecules dominated by pairing were observed, as well as the axial shift of the core to each other.
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Affiliation(s)
- Katarzyna Merkel
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, ul. 75 Pułku Piechoty, 41-500 Chorzów, Poland
| | - Barbara Loska
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, ul. 75 Pułku Piechoty, 41-500 Chorzów, Poland
| | - Yuki Arakawa
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan
| | - Georg H. Mehl
- Department of Chemistry, University of Hull, Hull HU6 7RX, UK
| | - Jakub Karcz
- Faculty of Advanced Technologies and Chemistry, Military University of Technology, 00-908 Warszawa, Poland
| | - Antoni Kocot
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, ul. 75 Pułku Piechoty, 41-500 Chorzów, Poland
- Correspondence: ; Tel.: +48-32-3497630
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2
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Kocot A, Loska B, Arakawa Y, Mehl GH, Merkel K. Study of the Experimental and Simulated Vibrational Spectra Together with Conformational Analysis of Thioether Cyanobiphenyl-Based Liquid Crystal Dimers. Int J Mol Sci 2022; 23:ijms23148005. [PMID: 35887352 PMCID: PMC9316788 DOI: 10.3390/ijms23148005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 07/15/2022] [Accepted: 07/18/2022] [Indexed: 11/16/2022] Open
Abstract
Infrared spectroscopy (IR) and quantum chemistry calculations that are based on the density functional theory (DFT) have been used to study the structure and molecular interactions of the nematic and twist-bend phases of thioether-linked dimers. Infrared absorbance measurements were conducted in a polarized beam for a homogeneously aligned sample in order to obtain more details about the orientation of the vibrational transition dipole moments. The distributions to investigate the structure and conformation of the molecule dihedral angle were calculated. The calculated spectrum was compared with the experimental infrared spectra and as a result, detailed vibrational assignments are reported.
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Affiliation(s)
- Antoni Kocot
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, ul. 75. Pułku Piechoty, 41-500 Chorzów, Poland; (A.K.); (B.L.)
| | - Barbara Loska
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, ul. 75. Pułku Piechoty, 41-500 Chorzów, Poland; (A.K.); (B.L.)
| | - Yuki Arakawa
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan;
| | - Georg H. Mehl
- Department of Chemistry, University of Hull, Hull HU6 7RX, UK;
| | - Katarzyna Merkel
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, ul. 75. Pułku Piechoty, 41-500 Chorzów, Poland; (A.K.); (B.L.)
- Correspondence: ; Tel.: +48-32-349-7630
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3
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The Beauty of Twist-Bend Nematic Phase: Fast Switching Domains, First Order Fréedericksz Transition and a Hierarchy of Structures. CRYSTALS 2021. [DOI: 10.3390/cryst11060621] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The twist-bend nematic phase (NTB) exhibits a complicated hierarchy of structures responsible for several intriguing properties presented here. These are: the observation of a fast electrooptic response, the exhibition of a large electroclinic effect, and the observation of an unusual pattern of the temperature dependence of birefringence of bent-shaped bimesogens in parallel-rubbed planar-aligned cells. These unusual effects inspired the use of highly sophisticated techniques that led to the discovery of the twist-bend nematic phase. Results of the optical retardation of a parallel-rubbed planar-aligned cell show that the ‘heliconical angle’ (the angle the local director makes with the optical axis) starts increasing in the high temperature N phase, it exhibits a jump at the N–NTB transition temperature and continues to increase in magnitude with a further reduction in temperature. The liquid crystalline parallel-rubbed planar-aligned and twist-aligned cells in this phase exhibit fascinating phenomena such as a demonstration of the beautiful stripes and dependence of their periodicity on temperature. The Fréedericksz transition in the NTB phase is found to be of the first order both in rubbed planar and homeotropic-aligned cells, in contrast to the second order transition exhibited by a conventional nematic phase. This transition shows a significant hysteresis as well as an abrupt change in the orientation of the director as a function of the applied electric field. Hierarchical structures are revealed using the technique of polymer templating the structure of the liquid crystalline phase of interest, and imaging of the resulting structure by scanning electron microscopy.
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Pocock EE, Mandle RJ, Goodby JW. Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases. Molecules 2021; 26:532. [PMID: 33498518 PMCID: PMC7864162 DOI: 10.3390/molecules26030532] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 11/16/2022] Open
Abstract
Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (NTB) phases. While the features that give rise to NTB phase formation are now somewhat understood, a comparable structure-property relationship governing the formation of layered (smectic) phases from the NTB phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both NTB and intercalated smectic phases. The higher temperature smectic phase is assigned as SmCA based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ''X'' phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.
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Affiliation(s)
- Emily E. Pocock
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
| | - Richard J. Mandle
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - John W. Goodby
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
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Mandle RJ, Goodby JW. Order parameters, orientational distribution functions and heliconical tilt angles of oligomeric liquid crystals. Phys Chem Chem Phys 2019; 21:6839-6843. [DOI: 10.1039/c9cp00736a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Twist-bend (TB) phases possess a local helical structure with a pitch length of a few nanometers. X-ray scattering experiments on aligned samples of dimeric and oligomeric materials allows the orientational order parameters, orientational distribution functions and heliconical tilt angles to be calculated.
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Mandle RJ, Goodby JW. A novel nematic-like mesophase induced in dimers, trimers and tetramers doped with a high helical twisting power additive. SOFT MATTER 2018; 14:8846-8852. [PMID: 30357232 DOI: 10.1039/c8sm01389f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
From the observation of a previously undiscovered nematic-like mesophase (NX) by Archbold et al., we report on several new binary liquid-crystalline mixtures between the high helical twisting power dopant RM1041 and a selection of dimers with varying average bend angles and conformational landscapes. We also report on mixtures between RM1041 and oligomeric LC materials. We find that dimers and oligomers exhibit not only chiral nematic and twist-bend modulated phases, but also the same NX phase reported by Archbold, indicating that this state of matter (the structure of which is yet to be definitively characterised) is exhibited by a wide range of materials. Mixtures of the dimer CB9CB with a selection of different chiral dopants suggest that it is the helical twisting power of the chiral additive that is responsible incidence of the NX phase.
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Mandle RJ, Goodby JW. Optically active bimesogens incorporating branched central spacers. RSC Adv 2018; 8:18542-18548. [PMID: 35541138 PMCID: PMC9080582 DOI: 10.1039/c8ra02075b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 05/14/2018] [Indexed: 11/24/2022] Open
Abstract
In the current fascination with liquid crystalline dimers, bimesogens and oligomers the role of the central spacer in these systems has perhaps been somewhat neglected. In compound 1, a phenyl 4-cyanobenzoate bimesogen, the central spacer incorporates a methyl group at the 2-position and is therefore chiral. The helical twisting power of 1, measured in both 5CB and E7, was found to be 0.36 and 0.35 μm-1 wt%-1 respectively. Compound 1 exhibited a monotropic chiral nematic phase, however no twist-bend modulated phase was observed. We prepared a number of analogues of 1 incorporating different mesogenic units and observe that those with a small aspect ratio are non mesogenic, whereas those with larger aspect ratios variously exhibit chiral nematic, TB, SmC and SmB phases.
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Affiliation(s)
- Richard J Mandle
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - John W Goodby
- Department of Chemistry, University of York Heslington York YO10 5DD UK
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Emsley JW, Lelli M, Luckhurst GR, Zimmermann H. ^{13}C NMR study of the director distribution adopted by the modulated nematic phases formed by liquid-crystal dimers with odd numbers of atoms in their spacers. Phys Rev E 2017; 96:062702. [PMID: 29347294 DOI: 10.1103/physreve.96.062702] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Indexed: 11/07/2022]
Abstract
The orientational order of the molecules in the bent mesogen CB6OCB has been studied throughout the range of temperature stability of both the N_{U} and N_{TB} liquid-crystal phases by ^{13}C NMR spectroscopy. These spectra provide local order parameters for the para axes of both of the nonequivalent cyanobiphenyl groups and show how they change on entering the twist-bend nematic phase. A key feature of the order parameters is a weak, but clear maximum in the temperature variation of the order parameter prior to the N_{TB} phase. This suggests that the directors in both the N_{U} and N_{TB} phases are tilted with respect to the magnetic field of the spectrometer. Significantly the conformational states of the spacer are comparable in both phases, although the low temperature nematic is chiral but not that at high temperature. It is proposed that the higher temperature, tilted phase could be the splay-bend nematic phase.
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Affiliation(s)
- J W Emsley
- Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
| | - M Lelli
- Department of Chemistry, Center for Magnetic Resonance, University of Florence, Sesto Fiorentino (FI) 50019, Italy
| | - G R Luckhurst
- Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
| | - H Zimmermann
- Max-Planck-Institut für Medizinische Forschung, Department of Biomolecular Mechanisms, D-69120 Heidelberg, Germany
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9
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Kumar A, Vanakaras AG, Photinos DJ. Polar Molecular Ordering in the N X Phase of Bimesogens and Enantiotopic Discrimination in the NMR Spectra of Rigid Prochiral Solutes. J Phys Chem B 2017; 121:10689-10703. [PMID: 29064695 DOI: 10.1021/acs.jpcb.7b08319] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The potential of mean torque governing the orientational ordering of prochiral solutes in the two nematic phases (N and NX) formed by certain classes of symmetric achiral bimesogens is formulated and used for the analysis of existing NMR measurements on solutes of various symmetries dissolved in the two phases. Three distinct attributes of the solvent phase, namely polarity of the orientational ordering, chirality of the constituent molecules, and spatial modulation of the local director, are identified as underlying three possible mechanisms for the generation of chiral asymmetry in the low temperature nematic phase (NX). The role and quantitative contribution of each mechanism to enantiotopic discrimination in the NX phase are presented and compared with the case of the conventional chiral nematic phase (N*). It is found that polar ordering is essential for the appearance of enantiotopic discrimination in small rigid solutes dissolved in the NX phase and that such discrimination is restricted to solutes belonging to the point group symmetries Cs and C2v.
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Affiliation(s)
- Anant Kumar
- Department of Materials Science, University of Patras , Patras 26504, Greece
| | | | - Demetri J Photinos
- Department of Materials Science, University of Patras , Patras 26504, Greece
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10
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Al-Janabi A, Mandle RJ, Goodby J. Isomeric trimesogens exhibiting modulated nematic mesophases. RSC Adv 2017. [DOI: 10.1039/c7ra10261e] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A simple deprotection/etherification strategy enables us to prepare oligomeric liquid-crystalline materials with ease, and unearth a potentially new mesophase.
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11
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Salili SM, Xiang J, Wang H, Li Q, Paterson DA, Storey JMD, Imrie CT, Lavrentovich OD, Sprunt SN, Gleeson JT, Jákli A. Magnetically tunable selective reflection of light by heliconical cholesterics. Phys Rev E 2016; 94:042705. [PMID: 27841485 DOI: 10.1103/physreve.94.042705] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Indexed: 06/06/2023]
Abstract
We present studies of chiral nematic liquid crystals composed of flexible dimer molecules subject to large dc magnetic fields between 0 and 31 T. We observe that these fields lead to selective reflection of light depending on temperature and magnetic field. The band of reflected wavelengths can be tuned from ultraviolet to beyond the IR-C band. A similar effect induced by electric fields has been presented previously, and was explained by a field-induced oblique-heliconical director deformation in accordance with early theoretical predictions. The use of magnetic field here instead of electric field allows precise measurements of some material constants and holds promise for wireless tuning of selective reflection.
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Affiliation(s)
- S M Salili
- Chemical Physics Interdisciplinary Program & Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - J Xiang
- Chemical Physics Interdisciplinary Program & Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - H Wang
- Chemical Physics Interdisciplinary Program & Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - Q Li
- Chemical Physics Interdisciplinary Program & Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - D A Paterson
- Department of Chemistry, University of Aberdeen, AB24 3UE Scotland, United Kingdom
| | - J M D Storey
- Department of Chemistry, University of Aberdeen, AB24 3UE Scotland, United Kingdom
| | - C T Imrie
- Department of Chemistry, University of Aberdeen, AB24 3UE Scotland, United Kingdom
| | - O D Lavrentovich
- Chemical Physics Interdisciplinary Program & Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - S N Sprunt
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
| | - J T Gleeson
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
| | - A Jákli
- Chemical Physics Interdisciplinary Program & Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
- Complex Fluid Group, Wigner Research Centre, Budapest, Hungary
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12
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Mandle RJ. The dependency of twist-bend nematic liquid crystals on molecular structure: a progression from dimers to trimers, oligomers and polymers. SOFT MATTER 2016; 12:7883-7901. [PMID: 27722733 DOI: 10.1039/c6sm01772j] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This article gives an overview on recent developments concerning the twist-bend nematic phase. The twist-bend nematic phase has been discussed as the missing link between the uniaxial nematic mesophase (N) and the helical chiral nematic phase (N*). After an introduction discussing the key physical properties of the NTB phase and the methods used to identify the twist-bend nematic mesophase this review focuses on structure property relationships and molecular features that govern the incidence of this phase.
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Affiliation(s)
- Richard J Mandle
- Department of Chemistry, University of York, York, YO10 5DD, UK.
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13
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Mandle RJ, Goodby JW. A Liquid Crystalline Oligomer Exhibiting Nematic and Twist-Bend Nematic Mesophases. Chemphyschem 2016; 17:967-70. [PMID: 26777310 DOI: 10.1002/cphc.201600038] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Indexed: 11/12/2022]
Abstract
The twist-bend nematic phase (NTB ) has been described as the structural link between the untilted uniaxial nematic phase (N) and the helical chiral nematic phase (N*). The NTB phase exhibits phenomena of fundamental importance to science, that is, 1) the spontaneous formation of a helical pitch on the nanometer scale in a fluid and 2) the spontaneous breaking of mirror symmetry, leading to the emergence of chiral domains in an achiral system. In this Communication, we present a study on T49 [bis(4-(9-(4-((4-cyanobenzoyl)oxy)phenyl)nonyl)phenyl) 4,4'-(nonane-1,9-diyl)dibenzoate], a liquid-crystalline oligomer exhibiting the twist-bend nematic phase, which has a molecular length that is of comparable dimensions to the sub-10 nm pitch determined for CB9CB, and provide new insights into the differentiation between the nano- and macro-science for self-assembling supermolecular systems.
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Affiliation(s)
- Richard J Mandle
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingdom.
| | - John W Goodby
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, United Kingdom
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14
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López DO, Robles-Hernández B, Salud J, de la Fuente MR, Sebastián N, Diez-Berart S, Jaen X, Dunmur DA, Luckhurst GR. Miscibility studies of two twist-bend nematic liquid crystal dimers with different average molecular curvatures. A comparison between experimental data and predictions of a Landau mean-field theory for the NTB–N phase transition. Phys Chem Chem Phys 2016; 18:4394-404. [DOI: 10.1039/c5cp07605f] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have developed a Landau model that predicts a first order twist-bend nematic–nematic phase transition.
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Affiliation(s)
- D. O. López
- Grup de Propietats Físiques dels Materials (GRPFM-GCMM)
- Departament de Física
- E.T.S.E.I.B
- Universitat Politècnica de Catalunya
- 647 08028 Barcelona
| | - B. Robles-Hernández
- Grup de Propietats Físiques dels Materials (GRPFM-GCMM)
- Departament de Física
- E.T.S.E.I.B
- Universitat Politècnica de Catalunya
- 647 08028 Barcelona
| | - J. Salud
- Grup de Propietats Físiques dels Materials (GRPFM-GCMM)
- Departament de Física
- E.T.S.E.I.B
- Universitat Politècnica de Catalunya
- 647 08028 Barcelona
| | - M. R. de la Fuente
- Departamento de Física Aplicada II
- Facultad de Ciencia y Tecnología
- Universidad del País Vasco
- E-48080 Bilbao
- Spain
| | - N. Sebastián
- Institute for Experimental Physics
- Otto-von-Guerike Universität Magdeburg
- ANP
- 39106 Magdeburg
- Germany
| | - S. Diez-Berart
- Grup de Propietats Físiques dels Materials (GRPFM-GCMM)
- Departament de Física
- E.T.S.E.I.B
- Universitat Politècnica de Catalunya
- 647 08028 Barcelona
| | - X. Jaen
- Grup de Propietats Físiques dels Materials (GRPFM-GCMM)
- Departament de Física
- E.T.S.E.I.B
- Universitat Politècnica de Catalunya
- 647 08028 Barcelona
| | - D. A. Dunmur
- School of Physics and Astronomy
- University of Manchester
- Manchester M13 9PL
- UK
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15
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Emsley JW, Lelli M, Joy H, Tamba MG, Mehl GH. Similarities and differences between molecular order in the nematic and twist-bend nematic phases of a symmetric liquid crystal dimer. Phys Chem Chem Phys 2016; 18:9419-30. [DOI: 10.1039/c5cp07304a] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Carbon-13 chemical shift anisotropies reveal an unusual temperature dependence of the order parameters, Szz, for the difluoroterphenyl groups in the normal nematic, N and the twist-bend nematic, NTB, phases.
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Affiliation(s)
- J. W. Emsley
- Department of Chemistry
- University of Southampton
- Southampton SO17 1BJ
- UK
| | - M. Lelli
- Institut des Sciences Analytiques
- Centre RMN à Très Hauts Champs (CRMN)
- 69100 Villeurbanne
- France
| | - H. Joy
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - M.-G. Tamba
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - G. H. Mehl
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
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16
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Mandle RJ, Goodby JW. Intercalated soft-crystalline mesophase exhibited by an unsymmetrical twist-bend nematogen. CrystEngComm 2016. [DOI: 10.1039/c6ce02123a] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Robles-Hernández B, Sebastián N, de la Fuente MR, López DO, Diez-Berart S, Salud J, Ros MB, Dunmur DA, Luckhurst GR, Timimi BA. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric, (2)H NMR, and calorimetric study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:062505. [PMID: 26764709 DOI: 10.1103/physreve.92.062505] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Indexed: 06/05/2023]
Abstract
The nature of the nematic-nematic phase transition in the liquid crystal dimer 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and (2)H NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (N(TB)), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the N(TB)-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and (2)H magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the N(TB) phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. (2)H NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.
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Affiliation(s)
- Beatriz Robles-Hernández
- Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain
| | - Nerea Sebastián
- Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain
- Otto-von-Guericke Universitat Magdeburg, Institute for Experimental Physics, ANP, 39106 Magdeburg, Germany
| | - M Rosario de la Fuente
- Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain
| | - David O López
- Grup de Propietas Físiques dels Materials (GRPFM), Departament de Física i Enginyeria Nuclear, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Diagonal 647, E- 08028 Barcelona, Spain
| | - Sergio Diez-Berart
- Grup de Propietas Físiques dels Materials (GRPFM), Departament de Física i Enginyeria Nuclear, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Diagonal 647, E- 08028 Barcelona, Spain
| | - Josep Salud
- Grup de Propietas Físiques dels Materials (GRPFM), Departament de Física i Enginyeria Nuclear, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Diagonal 647, E- 08028 Barcelona, Spain
| | - M Blanca Ros
- Departamento de Química Orgánica, Facultad de Ciencias-Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, E-50009 Zaragoza, Spain
| | - David A Dunmur
- Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
| | - Geoffrey R Luckhurst
- Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
| | - Bakir A Timimi
- Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
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Wang Y, Singh G, Agra-Kooijman DM, Gao M, Bisoyi HK, Xue C, Fisch MR, Kumar S, Li Q. Room temperature heliconical twist-bend nematic liquid crystal. CrystEngComm 2015. [DOI: 10.1039/c4ce02502d] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Tamba MG, Salili SM, Zhang C, Jákli A, Mehl GH, Stannarius R, Eremin A. A fibre forming smectic twist–bent liquid crystalline phase. RSC Adv 2015. [DOI: 10.1039/c4ra14669g] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We demonstrate the nanostructure and filament formation of a novel liquid crystal phase of a dimeric mesogen below the twist–bend nematic phase.
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Affiliation(s)
- M. G. Tamba
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - S. M. Salili
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - C. Zhang
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - A. Jákli
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - G. H. Mehl
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - R. Stannarius
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - A. Eremin
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
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20
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Salili SM, Kim C, Sprunt S, Gleeson JT, Parri O, Jákli A. Flow properties of a twist-bend nematic liquid crystal. RSC Adv 2014. [DOI: 10.1039/c4ra10008e] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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21
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Challa PK, Borshch V, Parri O, Imrie CT, Sprunt SN, Gleeson JT, Lavrentovich OD, Jákli A. Twist-bend nematic liquid crystals in high magnetic fields. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:060501. [PMID: 25019707 DOI: 10.1103/physreve.89.060501] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Indexed: 06/03/2023]
Abstract
We present magneto-optic measurements on two materials that form the recently discovered twist-bend nematic (N_{tb}) phase. This intriguing state of matter represents a fluid phase that is orientationally anisotropic in three directions and also exhibits translational order with periodicity several times larger than the molecular size. N_{tb} materials may also spontaneously form a visible, macroscopic stripe texture. We show that the optical stripe texture can be persistently inhibited by a magnetic field, and a 25T external magnetic field depresses the N-N_{tb} phase transition temperature by almost 1{∘}C. We propose a quantitative mechanism to account for this shift and suggest a Helfrich-Hurault-type mechanism for the optical stripe formation.
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Affiliation(s)
- P K Challa
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
| | - V Borshch
- Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - O Parri
- Merck Chemicals Ltd., Chilworth Technical Centre, University Parkway, Southampton SO16 7QD, United Kingdom
| | - C T Imrie
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3UE, Scotland
| | - S N Sprunt
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
| | - J T Gleeson
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
| | - O D Lavrentovich
- Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
| | - A Jákli
- Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA
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22
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Emsley JW, Lelli M, Lesage A, Luckhurst GR. A comparison of the conformational distributions of the achiral symmetric liquid crystal dimer CB7CB in the achiral nematic and chiral twist-bend nematic phases. J Phys Chem B 2013; 117:6547-57. [PMID: 23634827 DOI: 10.1021/jp4001219] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The sets of residual dipolar couplings between carbon and hydrogen nuclei obtained from the proton-encoded (13)C 2D NMR experiment are used to investigate the conformational changes which occur when the achiral symmetric liquid crystal dimer CB7CB changes from the achiral nematic to the chiral twist-bend nematic phase. It is found that these changes are a consequence of the chirality of the twist-bend nematic phase, rather than being the driving force for the stability of this phase.
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Affiliation(s)
- James W Emsley
- Centre RMN à Très Hauts Champs, CNRS/ENS Lyon/UCB-Lyon 1, Université de Lyon, 5 rue de la Doua, 69100 Villeurbanne, France.
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23
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Castles F. Liquid crystal research highlights. LIQUID CRYSTALS TODAY 2013. [DOI: 10.1080/1358314x.2013.813726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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24
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Greco C, Luckhurst GR, Ferrarini A. Enantiotopic discrimination and director organization in the twist-bend nematic phase. Phys Chem Chem Phys 2013; 15:14961-5. [DOI: 10.1039/c3cp52222a] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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