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Majewska MM, Forsyth E, Pociecha D, Wang C, Storey JMD, Imrie CT, Gorecka E. Controlling spontaneous chirality in achiral materials: liquid crystal oligomers and the heliconical twist-bend nematic phase. Chem Commun (Camb) 2022; 58:5285-5288. [PMID: 35398878 DOI: 10.1039/d1cc07012f] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Liquid crystal oligomers, namely dimers, trimers and tetramers, consisting of cyanobiphenyl and benzylideneaniline-based mesogenic units connected by either linear or bent alkoxy or alkyl spacers are reported. These materials, although built from achiral molecules, show the spontaneously chiral heliconical twist-bend nematic (NTB) phase. We report the relationships between the shape of the oligomer, and the NTB phase stability, the temperature dependence of the helical pitch length and tilt angle, birefringence, and elastic constants.
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Affiliation(s)
- M M Majewska
- Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089 Warsaw, Poland.
| | - E Forsyth
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen AB24 3UE, UK
| | - D Pociecha
- Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089 Warsaw, Poland.
| | - C Wang
- Advanced Light Source, LBNL, Berkeley, CA 94720, USA
| | - J M D Storey
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen AB24 3UE, UK
| | - C T Imrie
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen AB24 3UE, UK
| | - E Gorecka
- Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089 Warsaw, Poland.
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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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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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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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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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