1
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Sabury S, Xu Z, Saiev S, Davies D, Österholm AM, Rinehart JM, Mirhosseini M, Tong B, Kim S, Correa-Baena JP, Coropceanu V, Jurchescu OD, Brédas JL, Diao Y, Reynolds JR. Non-covalent planarizing interactions yield highly ordered and thermotropic liquid crystalline conjugated polymers. MATERIALS HORIZONS 2024; 11:3352-3363. [PMID: 38686501 DOI: 10.1039/d3mh01974h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Controlling the multi-level assembly and morphological properties of conjugated polymers through structural manipulation has contributed significantly to the advancement of organic electronics. In this work, a redox active conjugated polymer, TPT-TT, composed of alternating 1,4-(2-thienyl)-2,5-dialkoxyphenylene (TPT) and thienothiophene (TT) units is reported with non-covalent intramolecular S⋯O and S⋯H-C interactions that induce controlled main-chain planarity and solid-state order. As confirmed by density functional theory (DFT) calculations, these intramolecular interactions influence the main chain conformation, promoting backbone planarization, while still allowing dihedral rotations at higher kinetic energies (higher temperature), and give rise to temperature-dependent aggregation properties. Thermotropic liquid crystalline (LC) behavior is confirmed by cross-polarized optical microscopy (CPOM) and closely correlated with multiple thermal transitions observed by differential scanning calorimetry (DSC). This LC behavior allows us to develop and utilize a thermal annealing treatment that results in thin films with notable long-range order, as shown by grazing-incidence X-ray diffraction (GIXD). Specifically, we identified a first LC phase, ranging from 218 °C to 107 °C, as a nematic phase featuring preferential face-on π-π stacking and edge-on lamellar stacking exhibiting a large extent of disorder and broad orientation distribution. A second LC phase is observed from 107 °C to 48 °C, as a smectic A phase featuring sharp, highly ordered out-of-plane lamellar stacking features and sharp tilted backbone stacking peaks, while the structure of a third LC phase with a transition at 48 °C remains unclear, but resembles that of the solid state at ambient temperature. Furthermore, the significance of thermal annealing is evident in the ∼3-fold enhancement of the electrical conductivity of ferric tosylate-doped annealed films reaching 55 S cm-1. More importantly, thermally annealed TPT-TT films exhibit both a narrow distribution of charge-carrier mobilities (1.4 ± 0.1) × 10-2 cm2 V-1 s-1 along with a remarkable device yield of 100% in an organic field-effect transistor (OFET) configuration. This molecular design approach to obtain highly ordered conjugated polymers in the solid state affords a deeper understanding of how intramolecular interactions and repeat-unit symmetry impact liquid crystallinity, solution aggregation, solution to solid-state transformation, solid-state morphology, and ultimately device applications.
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Affiliation(s)
- Sina Sabury
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Zhuang Xu
- Department of Chemical and Biomolecular Engineering, Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA
| | - Shamil Saiev
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721-0041, USA
| | - Daniel Davies
- Department of Chemical and Biomolecular Engineering, Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA
| | - Anna M Österholm
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Joshua M Rinehart
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Motahhare Mirhosseini
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Benedict Tong
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Sanggyun Kim
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Juan-Pablo Correa-Baena
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Veaceslav Coropceanu
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721-0041, USA
| | - Oana D Jurchescu
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Jean-Luc Brédas
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721-0041, USA
| | - Ying Diao
- Department of Chemical and Biomolecular Engineering, Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA
| | - John R Reynolds
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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Ožegović A, Knežević A, Novak J, Šegota S, Davidson P, Lesac A. The Interplay of Spacer Chirality and Parity in Mesogenic Dimers. Chemphyschem 2024; 25:e202400065. [PMID: 38406969 DOI: 10.1002/cphc.202400065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 02/23/2024] [Accepted: 02/23/2024] [Indexed: 02/27/2024]
Abstract
Introducing chirality into soft materials, including liquid crystals (LCs), profoundly impacts their self-organization and physical properties. In this study, we synthesized a novel series of LC dimers with a chiral center as part of their flexible spacer. The dimers were prepared in racemic and enantiomerically pure forms. Their spacer length and parity were varied to investigate the effect of spacer chirality and parity on mesomorphic behavior and on chiral induction in the nematic phase of achiral mesogens. Our results show that the even-membered chiral dimers only have chiral nematic phases. In contrast, the odd-membered dimers display rich mesomorphism, including the intriguing blue phase (BP) and chiral form of the twist-bend nematic phase (N*TB). The observed significant difference in the 3D surface morphology between the racemic and chiral forms of the N*TB phase suggests that the chiral moiety in the spacer promotes a chiral hierarchy. Furthermore, the chiral dimers show a prominent odd-even effect in the helical twisting power in nematic hosts. These findings highlight the importance of the position of the chiral group within the dimeric molecule and provide new insights into how intrinsic chirality in the spacer affects the overall structural chirality.
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Affiliation(s)
| | | | - Jurica Novak
- University of Rijeka, Center for Artificial Intelligence and Cyber Security, Radmile Matejčić 2, 51000, Rijeka, Croatia
| | - Suzana Šegota
- Ruđer Bošković Institute, Bijenička 54, 10000, Zagreb, Croatia
| | - Patrick Davidson
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, 91405, Orsay, France
| | - Andreja Lesac
- Ruđer Bošković Institute, Bijenička 54, 10000, Zagreb, Croatia
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3
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Zavvou EE, Ramou E, Ahmed Z, Welch C, Mehl GH, Vanakaras AG, Karahaliou PK. Dipole-dipole correlations in the nematic phases of symmetric cyanobiphenyl dimers and their binary mixtures with 5CB. SOFT MATTER 2023; 19:9224-9238. [PMID: 37997929 DOI: 10.1039/d3sm01017a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
We report on the temperature dependence of birefringence and of the static dielectric permittivity tensor in a series of binary mixtures between the symmetric, bent-shaped, 1'',9''-bis(4-cyanobiphenyl-4'-yl)nonane (CB9CB) dimer and the monomeric nematogen 5CB. In the studied composition range the mixtures exhibit two nematic phases with distinct birefringence and dielectric features. Birefringence measurements are used to estimate the temperature dependence of the tilt between the axis defining the nanoscale helical modulation of the low temperature nematic phase with the (local) direction of the maximal alignment of the cyanobiphenyl units. Planar as well as magnetically and/or electrically aligned samples are used to measure the perpendicular and parallel components of the dielectric permittivity in both nematic phases. A self-consistent molecular field theory that takes into account flexibility and symmetry of the constituent mesogens is introduced for the calculation of order parameters and intra-molecular orientational dipolar correlations of the flexible dimers as a function of temperature/concentration. Utilising the tilt angle, as calculated from the birefringence measurements, and the predictions of the molecular theory, dielectric permittivity is modelled in the framework of the anisotropic version of the Kirkwood-Fröhlich theory. Using the inter-molecular Kirkwood correlation factors as adjustable parameters, excellent agreement between theory and permittivity measurements across the whole temperature range and composition of the mixtures is obtained. The importance of the orientational, intra- and inter-molecular, dipolar correlations, their relative impact on the static dielectric properties, as well as their connection with the local structure of the nematic phases of bent-shaped bimesogens, is discussed.
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Affiliation(s)
| | - Efthymia Ramou
- Department of Physics, University of Patras, 26504 Patras, Greece.
| | - Ziauddin Ahmed
- Department of Chemistry, University of Hull, HU6 7RX, UK
| | - Chris Welch
- Department of Chemistry, University of Hull, HU6 7RX, UK
| | - Georg H Mehl
- Department of Chemistry, University of Hull, HU6 7RX, UK
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4
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Aya S, Tang W, Kong X, Arakawa Y, Komatsu K, Tsuji H. Nontrivial ultraslow dynamics under electric-field in nematics of bent-shaped molecules. Phys Chem Chem Phys 2022; 25:297-303. [PMID: 36477024 DOI: 10.1039/d2cp02407a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
For over decades, nematic liquid crystals have been recognized as highly fluidic materials that respond to electric field on the millisecond scale. In contrast to traditional nematics with fast responsivity, we herein report nontrivial ultraslow electric-driven dynamics in bent-shaped nematic materials. Varying the alkyl chain spacers of bent-shaped cyanobiphenyl dimers (COOm and OCOm) shows a 'transition' in the dynamics behavior between the bent-dimeric and bent-core materials. Interestingly, with short alkyl chain spacers, COO2 exhibits unexpected ultra-slow dynamic pathways, i.e., "quasi-static" electrohydrodynamic convection. A significant observation is that the on/off-electro-switching time of COO2 is 10 000 times higher than that of typical nematic materials, which is the largest value reported ever in the kilo-second range. In addition, the threshold voltage for inducing the reorientation of the nematic director for COO2 is higher than 5 V, which is uncommon in traditional N materials. These properties are distinct from those of traditional nematic materials and discussed in terms of dielectric constants and electrohydrodynamic convection.
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Affiliation(s)
- Satoshi Aya
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China. .,Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology, Guangzhou 510640, China
| | - Wentao Tang
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China.
| | - Xian Kong
- South China Advanced Institute for Soft Matter Science and Technology (AISMST), School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China.
| | - Yuki Arakawa
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi, 441-8580, Japan.
| | - Kenta Komatsu
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi, 441-8580, Japan.
| | - Hideto Tsuji
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi, 441-8580, Japan.
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Sellarès J, Diego JA, López DO, Salud J, Robles-Hernández B, de la Fuente MR, Cañadas JC, Mudarra M, López de Rioja V, Levit R, Diez-Berart S. Comparative dielectric and thermally stimulated-depolarization-current studies of the liquid crystal dimers 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane and heptane and a binary mixture between them, close to the glass transition. Phys Rev E 2022; 106:054702. [PMID: 36559473 DOI: 10.1103/physreve.106.054702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 10/27/2022] [Indexed: 06/17/2023]
Abstract
We have performed dielectric spectroscopy and thermally stimulated-depolarization-current experiments to study the molecular dynamics of the twist-bend nematic phase close to the glass transition of two members of the 1″,7'-bis(4-cyanobiphenyl-4'-yl)alkane homologous series (CBnCB): the liquid crystal (LC) dimers CB9CB and CB7CB, as well as a binary mixture of both. By doping CB9CB with a small quantity of CB7CB, the crystallization is inhibited when cooling the sample down, while the bulk properties of CB9CB are retained and we can investigate the supercooled behavior close to the glass transition. The study reveals that the inter- and intramolecular interactions of the mixture are similar to those of pure CB9CB and confirms that there is a single glass transition in symmetric LC dimers.
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Affiliation(s)
- Jordi Sellarès
- DILAB, Departament de Física, E.S.E.I.A.A.T. Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spain
| | - José Antonio Diego
- DILAB, Departament de Física, E.S.E.I.A.A.T. Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spain
| | - David O López
- Grup de les Propietas Físiques del Materials (GRPFM), Departament de Física, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Avinguda Diagonal, 647, 08028 Barcelona, Spain
| | - Josep Salud
- Grup de les Propietas Físiques del Materials (GRPFM), Departament de Física, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Avinguda Diagonal, 647, 08028 Barcelona, Spain
| | - Beatriz Robles-Hernández
- Donostia International Physics Center, Manuel Lardizabal Ibilbidea 4, 20018 Donostia, Spain
- Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain
| | - María Rosario de la Fuente
- Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apartado 644, E-48080 Bilbao, Spain
| | - Juan Carlos Cañadas
- DILAB, Departament de Física, E.S.E.I.A.A.T. Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spain
| | - Miguel Mudarra
- DILAB, Departament de Física, E.S.E.I.A.A.T. Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spain
| | - Victor López de Rioja
- Grup de les Propietas Físiques del Materials (GRPFM), Departament de Física, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Avinguda Diagonal, 647, 08028 Barcelona, Spain
| | - Rafael Levit
- Caracterització Elèctrica dels Materials i Dispositius (CEMAD), Departament de Física, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Avinguda Diagonal, 647, 08028 Barcelona, Spain
| | - Sergio Diez-Berart
- Grup de les Propietas Físiques del Materials (GRPFM), Departament de Física, E.T.S.E.I.B. Universitat Politècnica de Catalunya, Avinguda Diagonal, 647, 08028 Barcelona, Spain
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6
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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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7
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Kubala P, Tomczyk W, Cieśla M. In silico study of liquid crystalline phases formed by bent-shaped molecules with excluded volume type interactions. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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8
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Shin Y, Zhou Z, Harder S, Zhang X, Yang DK. Reconfigurable liquid crystal diffraction grating based on flexoelectric effect. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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9
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Alshammari AF, Pociecha D, Walker R, Storey JMD, Gorecka E, Imrie CT. New patterns of twist-bend liquid crystal phase behaviour: the synthesis and characterisation of the 1-(4-cyanobiphenyl-4'-yl)-10-(4-alkylaniline-benzylidene-4'-oxy)decanes (CB10O· m). SOFT MATTER 2022; 18:4679-4688. [PMID: 35678154 DOI: 10.1039/d2sm00162d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The synthesis and characterisation of the 1-(4-cyanobiphenyl-4'-yl)-10-(4-alkylanilinebenzylidene-4'-oxy)decanes (CB10O·m) are reported. This series shows a rich liquid crystal polymorphism including twist-bend nematic and smectic phases. All the homologues reported exhibit an enantiotropic conventional nematic phase. For the homologues with m ≤ 10, the local packing in the nematic phases and the layer spacing in the smectic phases indicates an intercalated arrangement of the molecules. An intercalated smectic CA phase is observed if m/11 ≈ 0.5. Either side of this condition, the twist-bend nematic phase is observed, a novel pattern of behaviour for a series on increasing a terminal chain length. For longer chain lengths, m = 12, 14, 16 and 18, two twist-bend smectic C (SmCTB) phases are observed, and the packing of the molecules is now of a bilayer-type. The higher temperature variant is termed SmCTB-SH in which SH (single helix) refers to the presence of a short, distorted clock-type helix. In the lower temperature SmCTB-DH phase, an additional longer helix is superimposed on the short one, and DH denotes double helix.
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Affiliation(s)
- Ahlam F Alshammari
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, AB24 3UE Scotland, UK.
| | - Damian Pociecha
- University of Warsaw, Faculty of Chemistry, ul. Zwirki i Wigury 101, 02-089 ˙ Warsaw, Poland
| | - Rebecca Walker
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, AB24 3UE Scotland, UK.
| | - John M D Storey
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, AB24 3UE Scotland, UK.
| | - Ewa Gorecka
- University of Warsaw, Faculty of Chemistry, ul. Zwirki i Wigury 101, 02-089 ˙ Warsaw, Poland
| | - Corrie T Imrie
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, AB24 3UE Scotland, UK.
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10
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Kumar A. Dependency of the twist-bend nematic phase formation on the molecular shape of liquid crystal dimers: A view through the lens of DFT. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.118858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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11
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A Ten-Year Perspective on Twist-Bend Nematic Materials. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27092689. [PMID: 35566040 PMCID: PMC9102178 DOI: 10.3390/molecules27092689] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/20/2022] [Accepted: 04/20/2022] [Indexed: 11/16/2022]
Abstract
The discovery of the twist-bend nematic phase (NTB) is a milestone within the field of liquid crystals. The NTB phase has a helical structure, with a repeat length of a few nanometres, and is therefore chiral, even when formed by achiral molecules. The discovery and rush to understand the rich physics of the NTB phase has provided a fresh impetus to the design and characterisation of dimeric and oligomeric liquid crystalline materials. Now, ten years after the discovery of the NTB phase, we review developments in this area, focusing on how molecular features relate to the incidence of this phase, noting the progression from simple symmetrical dimeric materials towards complex oligomers, non-covalently bonded supramolecular systems.
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12
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Kocot A, Loska B, Arakawa Y, Merkel K. Structure of the twist-bend nematic phase with respect to the orientational molecular order of the thioether-linked dimers. Phys Rev E 2022; 105:044701. [PMID: 35590529 DOI: 10.1103/physreve.105.044701] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 03/09/2022] [Indexed: 06/15/2023]
Abstract
An analysis of the IR absorbance for the segmented functional groups of liquid crystal dimers mesogen and linker enabled the orientation order to be determined and information about the dipole interactions in the nematic and twist-bend nematic phases to be obtained. The long axis orientational order increases as the temperature decreases in the nematic phase, although much more slowly than for the classical nematics, and then reverses this trend in the twist-bend nematic phase due to the tilt of the molecules. In the nematic phase, the short axis of the molecule performs an isotropic uniform rotation and has a uniaxial alignment. In the twist-bend nematic phase, however, biaxial ordering occurs and grows significantly in accordance with the helical deformation of the director. Changes in the mean absorbance in the twist-bend nematic phase were observed: a decrease for the longitudinal dipole at the nematic-twist-bend nematic phase transition, thus emphasizing the antiparallel axial interaction of the dipoles, while the absorbance of the transverse dipoles remains unchanged up to 340 K, and then the latter become parallelly correlated.
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Affiliation(s)
- Antoni Kocot
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, 75 Pułku Piechoty 1a, Chorzów 41-500, Poland
| | - Barbara Loska
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, 75 Pułku Piechoty 1a, Chorzów 41-500, Poland
| | - Yuki Arakawa
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan
| | - Katarzyna Merkel
- Institute of Materials Engineering, Faculty of Science and Technology, University of Silesia, 75 Pułku Piechoty 1a, Chorzów 41-500, Poland
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Thioether-Linked Liquid Crystal Trimers: Odd-Even Effects of Spacers and the Influence of Thioether Bonds on Phase Behavior. MATERIALS 2022; 15:ma15051709. [PMID: 35268942 PMCID: PMC8911043 DOI: 10.3390/ma15051709] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/18/2022] [Accepted: 02/20/2022] [Indexed: 02/04/2023]
Abstract
We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3–11). All CBSnOBOnSCB homologs exhibited LC phases. Interestingly, even-n and odd-n homologs showed monotropic layered smectic A (SmA) and pseudo-layered twist-bend nematic (NTB) phases, respectively, below a nematic (N) phase. This alternate formation, which depends on spacer chain parity, is attributed to different average molecular shapes, which are associated with the relative orientations of the biphenyl moieties: linear and bent shapes for even-n and odd-n homologs, respectively. In addition, X-ray diffraction analysis indicated a strong cybotactic N phase tendency, with a triply intercalated structure. The phase-transition behavior and LC phase structures of thioether-linked CBSnOBOnSCB were compared with those of the all-ether-linked classic LC trimers CBOnOBOnOCB. Overall, thioether linkages endowed CBSnOBOnSCB with a monotropic LC tendency and lowered phase-transition temperatures, compared to those of CBOnOBOnOCB, for the same n. This is attributed to enhanced flexibility and bending (less molecular anisotropy) of the molecules, caused by the greater bond flexibility and smaller inner bond angles of the C–S–C bonds, compared to those of the C–O–C bonds.
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14
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Helical phases assembled from achiral molecules: Twist-bend nematic and helical filamentary B4 phases formed by mesogenic dimers. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118180] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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15
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Arakawa Y, Ishida Y, Komatsu K, Arai Y, Tsuji H. Thioether-linked benzylideneaniline-based twist-bend nematic liquid crystal dimers: Insights into spacer lengths, mesogenic arm structures, and linkage types. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132351] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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16
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Strachan GJ, Harrison WTA, Storey JMD, Imrie CT. Understanding the remarkable difference in liquid crystal behaviour between secondary and tertiary amides: the synthesis and characterisation of new benzanilide-based liquid crystal dimers. Phys Chem Chem Phys 2021; 23:12600-12611. [PMID: 34047739 DOI: 10.1039/d1cp01125a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A number of liquid crystal dimers have been synthesised and characterised containing secondary or tertiary (N-methyl) benzanilide-based mesogenic groups. The secondary amides all form nematic phases, and we present the first example of an amide to show the twist-bend nematic (NTB) phase. Only two of the corresponding N-methylated dimers formed a nematic phase and with greatly reduced nematic-isotropic transition temperatures. Characterisation using 2D ROESY NMR experiments, DFT geometry optimisation and X-ray diffraction reveal that there is a change in the preferred conformation of the benzanilide core on methylation, from Z to E. The rotational barrier around the N-C(O) bond has been measured using variable temperature 1H NMR spectroscopy. This dramatic change in shape accounts for the remarkable difference in liquid crystalline behaviour between these secondary and tertiary amide-based materials.
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Affiliation(s)
- Grant J Strachan
- Department of Chemistry, University of Aberdeen, Aberdeen, Scotland, UK.
| | | | - John M D Storey
- Department of Chemistry, University of Aberdeen, Aberdeen, Scotland, UK.
| | - Corrie T Imrie
- Department of Chemistry, University of Aberdeen, Aberdeen, Scotland, UK.
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17
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Walker R, Majewska M, Pociecha D, Makal A, Storey JM, Gorecka E, Imrie CT. Twist-Bend Nematic Glasses: The Synthesis and Characterisation of Pyrene-based Nonsymmetric Dimers. Chemphyschem 2021; 22:461-470. [PMID: 33369044 DOI: 10.1002/cphc.202000993] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Indexed: 12/17/2022]
Abstract
A selection of pyrene-based liquid crystal dimers have been prepared, containing either methylene-ether or diether linked spacers of varying length and parity. All the diether linked materials, CBOnO.Py (n=5, 6, 11, 12), exhibit conventional nematic and smectic A phases, with the exception of CBO11O.Py which is exclusively nematic. The methylene-ether linked dimer, CBnO.Py, with an even-membered spacer (n=5) was solely nematogenic, but odd-members (n=6, 8, 10) exhibited both nematic and twist-bend nematic phases. Replacement of the cyanobiphenyl fragment by cyanoterphenyl giving CT6O.Py, gave elevated melting and nematic-isotropic transition temperatures, and SmA and SmCA phases were observed on cooling the nematic phase. Intermolecular face-to-face associations of the pyrene moieties drive glass formation, and all these materials have a glass transition temperature at or above room temperature. The stability of the glassy twist-bend nematic phase allowed for its study using AFM, and the helical pitch length, PTB , was measured as 6.3 and 6.7 nm for CB6O.Py and CB8O.Py, respectively. These values are comparable to the shortest pitch of a twist-bend nematic phase measured to date.
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Affiliation(s)
- Rebecca Walker
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen, AB24 3UE, UK
| | - Magdalena Majewska
- Faculty of Chemistry, University of Warsaw, ul. Zwirki I Wigury 101, 02-089, Warsaw, Poland
| | - Damian Pociecha
- Faculty of Chemistry, University of Warsaw, ul. Zwirki I Wigury 101, 02-089, Warsaw, Poland
| | - Anna Makal
- Faculty of Chemistry, University of Warsaw, ul. Zwirki I Wigury 101, 02-089, Warsaw, Poland
| | - John Md Storey
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen, AB24 3UE, UK
| | - Ewa Gorecka
- Faculty of Chemistry, University of Warsaw, ul. Zwirki I Wigury 101, 02-089, Warsaw, Poland
| | - Corrie T Imrie
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen, AB24 3UE, UK
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18
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Arakawa Y, Komatsu K, Ishida Y, Igawa K, Tsuji H. Carbonyl- and thioether-linked cyanobiphenyl-based liquid crystal dimers exhibiting twist-bend nematic phases. Tetrahedron 2021. [DOI: 10.1016/j.tet.2020.131870] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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19
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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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20
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Forsyth E, Paterson DA, Cruickshank E, Strachan GJ, Gorecka E, Walker R, Storey JM, Imrie CT. Liquid crystal dimers and the twist-bend nematic phase: On the role of spacers and terminal alkyl chains. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114391] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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21
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Lewandowski W, Vaupotič N, Pociecha D, Górecka E, Liz-Marzán LM. Chirality of Liquid Crystals Formed from Achiral Molecules Revealed by Resonant X-Ray Scattering. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1905591. [PMID: 32529663 DOI: 10.1002/adma.201905591] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 03/14/2020] [Accepted: 03/16/2020] [Indexed: 05/21/2023]
Abstract
Intensive research on chiral liquid crystals (LCs) has been fueled by their actively tunable physicochemical properties and structural complexity, comparable to those of sophisticated natural materials. Herein, recent progress in the discovery of new classes of chiral LCs, enabled by a combination of nano- and macroscale investigations is reviewed. First, an overview is provided of liquid crystalline phases, made of chiral and achiral low-weight molecules, that exhibit chiral structure and/or chiral morphology. Then, recent progress in the discovery of new classes of chiral LCs, particularly enabled by the application of resonant X-ray scattering is described. It is shown that the method is sensitive to modulations of molecular orientation and therefore provides information hardly accessible by means of other techniques, such as the sense of helical structures or chirality transfer across length scales. Finally, a perspective is presented on the future scope, opportunities, and challenges in the field of chiral LCs, in particular related to nanocomposites.
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Affiliation(s)
- Wiktor Lewandowski
- Faculty of Chemistry, University of Warsaw, Pasteura 1 St., Warsaw, 02-093, Poland
| | - Nataša Vaupotič
- Department of Physics, University of Maribor, Koroška 160, Maribor, 2000, Slovenia
- Jozef Stefan Institute, Jamova 39, Ljubljana, 1000, Slovenia
| | - Damian Pociecha
- Faculty of Chemistry, University of Warsaw, Pasteura 1 St., Warsaw, 02-093, Poland
| | - Ewa Górecka
- Faculty of Chemistry, University of Warsaw, Pasteura 1 St., Warsaw, 02-093, Poland
| | - Luis M Liz-Marzán
- CIC biomaGUNE and CIBER-BBN, Paseo de Miramón 182, Donostia-San Sebastián, 20014, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, 48013, Spain
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22
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Matsuyama A. Phase transitions of heliconical smectic-C and heliconical nematic phases in banana-shaped liquid crystals. Phys Rev E 2020; 101:050701. [PMID: 32575293 DOI: 10.1103/physreve.101.050701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 05/10/2020] [Indexed: 11/07/2022]
Abstract
A mean-field theory is introduced to describe heliconical nematic (N_{TB}), heliconical smectic-C (S_{m}C_{TB}), and biaxial heliconical smectic-C (S_{m}C_{TB,b}) phases with mirror symmetry breaking. We extend our previous theories of the N_{TB} phase to the heliconical smectic-C phases, by taking into account one-dimensional spatial ordering of smectic layers. The calculated phase diagrams on the temperature-alkyl chain length plane show a rich variety of phase transitions: first- and second-order N_{TB}-S_{m}C_{TB} transitions, etc., including tricritical, tetracritical, and multicritical points. Our theory is qualitatively consistent with an experimental phase diagram.
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Affiliation(s)
- Akihiko Matsuyama
- Department of Physics and Information Technology, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502, Japan
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23
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Tomczyk W, Longa L. Role of molecular bend angle and biaxiality in the stabilization of the twist-bend nematic phase. SOFT MATTER 2020; 16:4350-4357. [PMID: 32347876 DOI: 10.1039/d0sm00078g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
What are the prerequisites for acquiring a stable twist-bend nematic phase (NTB)? Addressing this question has led to the synthesis of a vast number of new compounds, concluding each time that the molecule's shape is one of the predominant factors. Inspired by the expanding knowledge of different achiral bent-shaped molecules forming a twist-bend nematic phase, we reinvestigate the interplay between a molecule's bend angle and a molecule's arms molecular biaxiality. Employing our previously developed generalized mean-field model, we explore more obtuse bend angles. We observe direct phase transition sequences between locally biaxial and uniaxial variants of NTB, along with biaxial and uniaxial nematic phases. Additionally, we present a comprehensive overview of how phase diagrams evolve according to alterations in the value of the bend angle and the magnitude of biaxiality.
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Affiliation(s)
- Wojciech Tomczyk
- Institute of Theoretical Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
| | - Lech Longa
- Institute of Theoretical Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland.
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24
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Al-Janabi A, Mandle RJ. Utilising Saturated Hydrocarbon Isosteres of para Benzene in the Design of Twist-Bend Nematic Liquid Crystals. Chemphyschem 2020; 21:697-701. [PMID: 32078227 DOI: 10.1002/cphc.202000130] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Indexed: 11/09/2022]
Abstract
The nematic twist-bend (NTB ) liquid crystal phase possesses a local helical structure with a pitch length of a few nanometres and is the first example of spontaneous symmetry breaking in a fluid system. All known examples of the NTB phase occur in materials whose constituent mesogenic units are aromatic hydrocarbons. It is not clear if this is due to synthetic convenience or a bona fide structural requirement for a material to exhibit this phase of matter. In this work we demonstrate that materials consisting largely of saturated hydrocarbons can also give rise to this mesophase.
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Affiliation(s)
| | - Richard J Mandle
- Department of Chemistry, University of York, York, UK.,School of Physics and Astronomy, University of Leeds, Leeds, UK
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25
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Arakawa Y, Ishida Y, Tsuji H. Ether- and Thioether-Linked Naphthalene-Based Liquid-Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic-Arm Symmetry on the Incidence and Stability of the Twist-Bend Nematic Phase. Chemistry 2020; 26:3767-3775. [PMID: 31825562 DOI: 10.1002/chem.201905208] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 12/05/2019] [Indexed: 11/11/2022]
Abstract
The twist-bend nematic (NTB ) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent-shaped molecules is a hot topic of current liquid-crystal science. As opposed to the most common methylene-linked dimers, this study demonstrates chalcogen ether- and/or thioether-linked 6-(4-cyanophenyl)-2-naphthyl-based liquid-crystal dimers with symmetric and asymmetric π-conjugated mesogenic-arm structures that exhibit the NTB phase. Although the symmetric bis(ether)-linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)-linked dimer can form the NTB phase. All thioether-linked dimers form the NTB phase, wherein the dimers with asymmetric arms vitrify in the NTB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic-arm symmetry, and spacer length. It is revealed that thioether-linked dimers based on asymmetric π-conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of NTB phases and glassy NTB states at room temperature.
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Affiliation(s)
- Yuki Arakawa
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Yuko Ishida
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Hideto Tsuji
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
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26
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27
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Arakawa Y, Sasaki S, Igawa K, Tokita M, Konishi GI, Tsuji H. Birefringence and photoluminescence properties of diphenylacetylene-based liquid crystal dimers. NEW J CHEM 2020. [DOI: 10.1039/d0nj04426a] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We herein report phase transitions, mesomorphism, birefringence behavior and photoluminescence properties of symmetric liquid crystal (LC) dimers based on diphenylacetylene or tolane.
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Affiliation(s)
- Yuki Arakawa
- Department of Applied Chemistry and Life Science
- Graduate School of Engineering
- Toyohashi University of Technology
- Toyohashi
- Japan
| | - Shunsuke Sasaki
- Department of Chemistry
- University of Oxford
- Inorganic Chemistry Laboratory
- Oxford
- UK
| | - Kazunobu Igawa
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Fukuoka 816-8580
- Japan
| | - Masatoshi Tokita
- Department of Chemical Science and Engineering
- School of Materials and Chemical Technology
- Tokyo Institute of Technology
- Tokyo 152-8550
- Japan
| | - Gen-ichi Konishi
- Department of Chemical Science and Engineering
- School of Materials and Chemical Technology
- Tokyo Institute of Technology
- Tokyo 152-8550
- Japan
| | - Hideto Tsuji
- Department of Applied Chemistry and Life Science
- Graduate School of Engineering
- Toyohashi University of Technology
- Toyohashi
- Japan
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28
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Hähsler M, Behrens S. Dendritic Ligands for Magnetic Suspensions in Liquid Crystals. European J Org Chem 2019. [DOI: 10.1002/ejoc.201901450] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Martin Hähsler
- Karlsruhe Institute of Technology Institute of Catalysis Research and Technology Hermann‐von‐Helmholtz‐Platz 1 76344 Karlsruhe Germany
- Heidelberg University Institute of Inorganic Chemistry Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Silke Behrens
- Karlsruhe Institute of Technology Institute of Catalysis Research and Technology Hermann‐von‐Helmholtz‐Platz 1 76344 Karlsruhe Germany
- Heidelberg University Institute of Inorganic Chemistry Im Neuenheimer Feld 270 69120 Heidelberg Germany
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29
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Mandle RJ, Goodby JW. Molecular Flexibility and Bend in Semi-Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State. Chemistry 2019; 25:14454-14459. [PMID: 31483073 PMCID: PMC6899767 DOI: 10.1002/chem.201903677] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/03/2019] [Indexed: 11/12/2022]
Abstract
The NTB phase phases possess a local helical structure with a pitch length of a few nanometers and is typically exhibited by materials consisting of two rigid mesogenic units linked by a flexible oligomethylene spacer of odd parity, giving a bent shape. We report the synthesis and characterisation of two novel dimeric liquid crystals, and perform a computational study on 10 cyanobiphenyl dimers with varying linking groups, generating a large library of conformers for each compound; this allows us to present molecular bend angles as probability weighted averages of many conformers, rather than use a single conformer. We validate conformer libraries by comparison of interproton distances with those obtained from solution-based 1D 1 H NOESY NMR, finding good agreement between experiment and computational work. Conversely, we find that using any single conformer fails to reproduce experimental interproton distances. We find the use of a single conformer significantly overestimates the molecular bend angle while also ignoring flexibility; in addition, we show that the average bend angle and flexibility are both linked to the relative stability of the NTB phase.
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30
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31
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Hann JL, Mandle RJ. Pentaerythritol Derived Tetrapode Exhibiting a Nematic-Like Mesophase at Ambient Temperatures. Chemphyschem 2019; 20:1941-1945. [PMID: 31194279 DOI: 10.1002/cphc.201900585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Indexed: 11/09/2022]
Abstract
The nematic liquid-crystalline phase exhibits average orientational order, with no positional organisation. So-called modulated nematic phases exhibit this same orientational order with an additional spatially periodic modulation of the nematic director, the most common of which is the twist-bend nematic phase. We report a pentaerythritol derived tetrapode which exhibits a nematic-like mesophase at ambient temperature, and we denote this new mesophase 'NX ' to indicate a nematic phase of unknown structure. X-ray scattering experiments refute the possibility of positional order, yet optical textures are consistent with a periodic structure. We suggest that the mesophase exhibited by this material is a new type of nematic-like mesophase with some form of modulated structure. We find the NX phase to exhibit an electrooptic response consistent with a nematic-like phase.
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Affiliation(s)
- Jodie L Hann
- Department of Chemistry, University of York, York, UK, YO10 5DD
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32
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Herod JD, Bates MA, Whitwood AC, Bruce DW. Ionic N-phenylpyridinium tetracatenar mesogens: competing driving forces in mesophase formation and unprecedented difference in phase stabilisation within a homologous series. SOFT MATTER 2019; 15:4432-4436. [PMID: 31119242 DOI: 10.1039/c9sm00846b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ionic, tetracatenar liquid crystals containing an N-phenylpyridinum core are described; many of these compounds display a SmA phase, something extremely rare in tetracatenar materials. The competing forces driving mesophase formation lead to an unprecedented difference in phase stabilities for SmA and Colh phases.
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Affiliation(s)
- Jordan D Herod
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
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33
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Arakawa Y, Komatsu K, Tsuji H. Twist-bend nematic liquid crystals based on thioether linkage. NEW J CHEM 2019. [DOI: 10.1039/c8nj06456c] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
“Thioether”-based twist-bend nematogens.
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Affiliation(s)
- Yuki Arakawa
- Department of Applied Chemistry and Life Science
- Graduate School of Engineering
- Toyohashi University of Technology
- Toyohashi
- Japan
| | - Kenta Komatsu
- Department of Applied Chemistry and Life Science
- Graduate School of Engineering
- Toyohashi University of Technology
- Toyohashi
- Japan
| | - Hideto Tsuji
- Department of Applied Chemistry and Life Science
- Graduate School of Engineering
- Toyohashi University of Technology
- Toyohashi
- Japan
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34
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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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35
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KneŽević A, Sapunar M, Buljan A, Dokli I, Hameršak Z, Kontrec D, Lesac A. Fine-tuning the effect of π-π interactions on the stability of the N TB phase. SOFT MATTER 2018; 14:8466-8474. [PMID: 30324187 DOI: 10.1039/c8sm01569d] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The synthesis and liquid-crystalline properties are reported for novel bent-shaped dimers in which a naphthyl group has been incorporated into the mesogenic cores. In addition to the nematic and twist-bend nematic phase, a new liquid-crystalline phase was observed. The combined experimental and computational study demonstrated how the interplay between the molecular geometry and π-π interactions affects the thermal stability of the twist-bend nematic and nematic phases. Correlation between mesomorphic properties and molecular geometry revealed that a greater conformational diversity leads to a broader distribution of bend-angles and destabilization of the NTB phase. Qualitative correlation between the thermal behaviour and electronic structure of the molecules of a similar geometry suggested that the transition temperatures of both nematic phases depend on the relative contribution of dispersion and electrostatic energies which determines the strength of the π-π interactions. These results provide an insight into how subtle changes in chemical structure can be exploited to tune the intermolecular interactions and influence the thermal stability of the liquid crystalline phase.
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36
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Mandle RJ, Goodby JW. A Nanohelicoidal Nematic Liquid Crystal Formed by a Non-Linear Duplexed Hexamer. Angew Chem Int Ed Engl 2018; 57:7096-7100. [PMID: 29673016 PMCID: PMC6033141 DOI: 10.1002/anie.201802881] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 04/04/2018] [Indexed: 01/06/2023]
Abstract
The twist-bend modulated nematic liquid-crystal phase exhibits formation of a nanometre-scale helical pitch in a fluid and spontaneous breaking of mirror symmetry, leading to a quasi-fluid state composed of chiral domains despite being composed of achiral materials. This phase was only observed for materials with two or more mesogenic units, the manner of attachment between which is always linear. Non-linear oligomers with a H-shaped hexamesogen are now found to exhibit both nematic and twist-bend modulated nematic phases. This shatters the assumption that a linear sequence of mesogenic units is a prerequisite for this phase, and points to this state of matter being exhibited by a wider range of self-assembling structures than was previously envisaged. These results support the double helix model of the TB phase as opposed to the simple heliconical model. This new class of materials could act as low-molecular-weight surrogates for cross-linked liquid-crystalline elastomers.
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37
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Mandle RJ, Goodby JW. A Nanohelicoidal Nematic Liquid Crystal Formed by a Non-Linear Duplexed Hexamer. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201802881] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
| | - John W. Goodby
- Department of Chemistry; University of York; York YO10 5DD UK
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Mandle RJ. Designing Liquid-Crystalline Oligomers to Exhibit Twist-Bend Modulated Nematic Phases. CHEM REC 2018; 18:1341-1349. [DOI: 10.1002/tcr.201800010] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 04/09/2018] [Indexed: 01/28/2023]
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Mandle RJ, Goodby J. 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] [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. Methylene-linked liquid-crystalline dimers with chiral spacers are found to exhibit several mesophases, including the helicoidal twist-bend modulated nematic state.![]()
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Mandle RJ. The Shape of Things To Come: The Formation of Modulated Nematic Mesophases at Various Length Scales. Chemistry 2017; 23:8771-8779. [PMID: 28453914 PMCID: PMC5518215 DOI: 10.1002/chem.201701167] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Indexed: 11/22/2022]
Abstract
The twist-bend nematic (NTB ) phase is a recently discovered liquid-crystalline phase that exhibits macroscopic chirality even when formed from achiral materials, and as such presents a unique testbed for studies concerning the spontaneous breaking of mirror symmetry in soft matter. It is primarily exhibited by materials for which the molecular structure is composed of two rigid aromatic units (such as biphenyl connected by a flexible spacer). The local structure of the NTB phase is nematic-like-with molecules having an average orientational order but no positional order-with a nanoscale helix in which the pitch (i.e., the repeat distance of the helix) is of the order of several nanometres. A helix is chiral, and so the bulk NTB phase-in the absence of a biasing chiral environment-spontaneously separates into macroscopic domains of opposite handedness. After discussing the structure of this mesophase and its elucidation, this concept article presents the molecular factors that determine its incidence. The apparent dependency primarily on molecular shape and bend angle rather than particular functional group combinations manifests in this mesophase being exhibited on length scales far beyond those of simple liquid-crystalline dimers, not only in oligomers and polymers, but also in aqueous suspensions of micron sized helical particles.
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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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Mandle RJ, Goodby JW. Does Topology Dictate the Incidence of the Twist-Bend Phase? Insights Gained from Novel Unsymmetrical Bimesogens. Chemistry 2016; 22:18456-18464. [PMID: 27706844 PMCID: PMC5217080 DOI: 10.1002/chem.201604030] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Indexed: 11/21/2022]
Abstract
We prepared a significant number of unsymmetrical liquid-crystalline dimers that exhibit the twist-bend nematic phase; a state of matter that exhibits spontaneous breaking of mirror symmetry and, for some materials, a microsecond electrooptic response. A number of novel unsymmetrical bimesogens were synthesized and in comparing their thermal behaviour to previous literature examples, we have uncovered an unexpected relationship between the thermal stability of the nematic and NTB phases. This relationship demonstrates that molecular shape dictates the incidence of this fascinating phase of matter and leads us to speculate as to the existence of "twist-bend nematic phases" on length scales beyond those of the molecule.
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