1
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Eremin A, Murad A, Alaasar M. Shear-induced birefringence in an optically isotropic cubic liquid crystalline phase. SOFT MATTER 2022; 18:8315-8319. [PMID: 36300301 DOI: 10.1039/d2sm01148d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
We report an unusually strong flow-induced birefringence in an optically isotropic cubic phase occurring below the isotropic chiral conglomerate phase formed by a low-molecular-weight polycatenar mesogen. The transition into the birefringent state occurs thresholdless and the induced birefringence is comparable with that observed in polymeric systems. We suggest that the flow-induced deformation of the cubic structure is responsible for the strong rheo-optical response.
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Affiliation(s)
- Alexey Eremin
- Department of Nonlinear Phenomena, Institute for Physics Otto von Guericke University Magdeburg, Magdeburg, Germany.
| | - Ahmad Murad
- Department of Nonlinear Phenomena, Institute for Physics Otto von Guericke University Magdeburg, Magdeburg, Germany.
| | - Mohamed Alaasar
- Department of Chemistry, Martin-Luther University Halle-Wittenberg, 06120 Halle (Saale), Germany.
- Department of Chemistry, Cairo University, Giza, Egypt.
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2
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Alaasar M, Cai X, Kraus F, Giese M, Liu F, Tschierske C. Controlling ambidextrous mirror symmetry breaking in photosensitive supramolecular polycatenars by alkyl-chain engineering. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.118597] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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3
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Hockey-Stick Polycatenars: Network formation and transition from one dimensional to three-dimensional liquid crystalline phases. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.118613] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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4
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Shanker G, Srinatha M, Sandhya Kumari D, Ranjitha B, Alaasar M. Novel green synthetic approach for liquid crystalline materials using multi-component reactions. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118244] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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5
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Alaasar M, Cai X, Cao Y, Liu F. Transition from lamellar to nanostructure mesophases in azobenzene-based hockey-stick polycatenars. NEW J CHEM 2022. [DOI: 10.1039/d2nj03255d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Tuning from 1D to 3D mesophases by alkyl chain engineering. Multichain π-conjugated hockey-stick molecules form lamellar SmA and meso-structure Ia3̄d with continuous networks. The effect of the position of the central bent-core unit on helical self-assembly is discussed.
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Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt Mothes Str. 2, D-06120, Halle, Saale, Germany
- Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt
| | - Xiaoqian Cai
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, P. R. China
| | - Yu Cao
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, P. R. China
| | - Feng Liu
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, P. R. China
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6
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Azobenzene-based polycatenars: Investigation on photo switching properties and optical storage devices. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117341] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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7
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Alaasar M, Schmidt JC, Cai X, Liu F, Tschierske C. Controlling liquid and liquid crystalline network formation by core-fluorination of hydrogen bonded supramolecular polycatenars. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115870] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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8
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Abstract
We prepared and studied bent-core liquid crystalline (LC) compounds based on 1,3-disubstituted benzene in a central part and azo-linkage attached directly to this bent core. We designed three structures and checked their mesogenic properties, as well as photosensitivity. We found that two studied compounds revealed columnar LC mesophases, which we transformed to the isotropic phase under the illumination of UV light. We concluded that only one type of structural motif was not mesogenic. For LC compounds, we established phases and phase transition temperatures based on differential scanning calorimetry (DSC) measurements and observations in a polarizing microscope. To confirm phase identification, X-ray studies were performed and structural parameters describing the columnar phases supplied.
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9
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Kurachkina M, Nádasi H, Alaasar M, Tschierske C, Eremin A. Photomanipulation of the Mechanical Properties in a Liquid Crystal with Azo‐Containing Bent‐Core Mesogens. CHEMPHOTOCHEM 2020. [DOI: 10.1002/cptc.202000125] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | - Hajnalka Nádasi
- Otto von Guericke University Inst. of Physics 39016 Magdeburg Germany
| | - Mohamed Alaasar
- Martin Luther University Halle-Wittenberg Kurt Mothes Str. 2 D-06120 Halle (Saale) Germany
- Department of Chemistry Faculty of Science Cairo University Giza Egypt
| | - Carsten Tschierske
- Martin Luther University Halle-Wittenberg Kurt Mothes Str. 2 D-06120 Halle (Saale) Germany
| | - Alexey Eremin
- Otto von Guericke University Inst. of Physics 39016 Magdeburg Germany
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10
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Šmahel M, Poryvai A, Xiang Y, Pociecha D, Troha T, Novotná V, Svoboda J, Kohout M. Photosensitive bent-core nematic liquid crystals with various linking units in the side arms: Structure-properties relationships. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.112743] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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11
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Lehmann A, Alaasar M, Poppe M, Poppe S, Prehm M, Nagaraj M, Sreenilayam SP, Panarin YP, Vij JK, Tschierske C. Stereochemical Rules Govern the Soft Self-Assembly of Achiral Compounds: Understanding the Heliconical Liquid-Crystalline Phases of Bent-Core Mesogens. Chemistry 2020; 26:4714-4733. [PMID: 31859404 PMCID: PMC7186843 DOI: 10.1002/chem.201904871] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 12/15/2019] [Indexed: 11/16/2022]
Abstract
A series of bent-shaped 4-cyanoresorcinol bisterephthalates is reported. Some of these achiral compounds spontaneously form a short-pitch heliconical lamellar liquid-crystalline phase with incommensurate 3-layer pitch and the helix axis parallel to the layer normal. It is observed at the paraelectric-(anti)ferroelectric transition, if it coincides with the transition from random to uniform tilt and with the transition from anticlinic to synclinic tilt correlation of the molecules in the layers of the developing tilted smectic phase. For compounds with long chains the heliconical phase is only field-induced, but once formed it is stable in a distinct temperature range, even after switching off the field. The presence of the helix changes the phase properties and the switching mechanism from the naturally preferred rotation around the molecular long axis, which reverses the chirality, to a precession on a cone, which retains the chirality. These observations are explained by diastereomeric relations between two coexisting modes of superstructural chirality. One is the layer chirality, resulting from the combination of tilt and polar order, and the other one is the helical twist evolving between the layers. At lower temperature the helical structure is replaced by a non-tilted and ferreoelectric switching lamellar phase, providing an alternative non-chiral way for the transition from anticlinic to synclinic tilt.
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Affiliation(s)
- Anne Lehmann
- Department of ChemistryMartin Luther University Halle-WittenbergKurt Mothes Str. 206120Halle (Saale)Germany
| | - Mohamed Alaasar
- Department of ChemistryMartin Luther University Halle-WittenbergKurt Mothes Str. 206120Halle (Saale)Germany
- Department of ChemistryCairo University12613GizaEgypt
| | - Marco Poppe
- Department of ChemistryMartin Luther University Halle-WittenbergKurt Mothes Str. 206120Halle (Saale)Germany
| | - Silvio Poppe
- Department of ChemistryMartin Luther University Halle-WittenbergKurt Mothes Str. 206120Halle (Saale)Germany
| | - Marko Prehm
- Department of ChemistryMartin Luther University Halle-WittenbergKurt Mothes Str. 206120Halle (Saale)Germany
| | - Mamatha Nagaraj
- Department of Electronic and Electrical EngineeringTrinity College, Dublin, The University of DublinDublin2Ireland
| | - Sithara P. Sreenilayam
- Department of Electronic and Electrical EngineeringTrinity College, Dublin, The University of DublinDublin2Ireland
| | - Yuri P. Panarin
- Department of Electronic and Electrical EngineeringTrinity College, Dublin, The University of DublinDublin2Ireland
| | - Jagdish K. Vij
- Department of Electronic and Electrical EngineeringTrinity College, Dublin, The University of DublinDublin2Ireland
| | - Carsten Tschierske
- Department of ChemistryMartin Luther University Halle-WittenbergKurt Mothes Str. 206120Halle (Saale)Germany
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12
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Westphal E, Gallardo H, Poppe S, Prehm M, Tschierske C. Controlling the soft self-assembly of 1,3,4-oxadiazoles by carbosilane end-groups. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111362] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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13
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Alaasar M, Prehm M, Belau S, Sebastián N, Kurachkina M, Eremin A, Chen C, Liu F, Tschierske C. Polar Order, Mirror Symmetry Breaking, and Photoswitching of Chirality and Polarity in Functional Bent‐Core Mesogens. Chemistry 2019; 25:6362-6377. [DOI: 10.1002/chem.201806180] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 01/21/2019] [Indexed: 01/06/2023]
Affiliation(s)
- Mohamed Alaasar
- Institute of ChemistryMartin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
- Department of Chemistry, Faculty of ScienceCairo University Giza Egypt
| | - Marko Prehm
- Institute of ChemistryMartin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
| | - Sebastian Belau
- Department of Nonlinear Phenomena, Institute of PhysicsOtto von Guericke University Magdeburg Magdeburg Germany
| | - Nerea Sebastián
- Department of Nonlinear Phenomena, Institute of PhysicsOtto von Guericke University Magdeburg Magdeburg Germany
| | - Marharyta Kurachkina
- Department of Nonlinear Phenomena, Institute of PhysicsOtto von Guericke University Magdeburg Magdeburg Germany
| | - Alexey Eremin
- Department of Nonlinear Phenomena, Institute of PhysicsOtto von Guericke University Magdeburg Magdeburg Germany
| | - Changlong Chen
- State Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong University Xi'an 710049 P. R. China
| | - Feng Liu
- State Key Laboratory for Mechanical Behavior of MaterialsXi'an Jiaotong University Xi'an 710049 P. R. China
| | - Carsten Tschierske
- Institute of ChemistryMartin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
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14
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Oikawa R, Sasaki H, Takanishi Y, Sagisaka M, Yamamoto J, Yoshizawa A. Linear symmetric liquid crystal trimers exhibiting supramolecular chiral architectures. SOFT MATTER 2019; 15:3179-3187. [PMID: 30892358 DOI: 10.1039/c9sm00250b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We prepared a homologous series of achiral liquid crystal trimers (I-n) in which two phenylpyrimidine units and one biphenyl unit were connected via flexible spacers, and investigated the physical properties. All the trimers possessing odd-numbered methylene spacers exhibited soft crystalline chiral conglomerate phases. X-ray diffraction measurements reveal that they have an intercalated layer structure. On the other hand, the trimers possessing even-numbered spacers showed nematic and smectic C phases. We investigated the surface structures of odd-membered trimers in the soft crystalline phases using scanning electron microscopy. Trimers I-3 and I-5 were found to form cylindrical tubes, whereas trimers I-7, I-9 and I-11 toroidal pits. We discuss the formation of diverse supramolecular architectures in terms of the anisotropy of the chirality transfer.
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Affiliation(s)
- Ryuji Oikawa
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, 036-8561, Japan.
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15
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Yoshizawa A, Kurata M. Porous surface of an achiral trimer in the chiral conglomerate phase catalyzes a direct aldol reaction. NEW J CHEM 2019. [DOI: 10.1039/c9nj01913h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The honeycomb-like porous surface consisting of linear trimer molecules catalyzes the direct aldol reaction of acetone with benzaldehyde at room temperature to give racemic β-hydroxyketone.
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Affiliation(s)
- Atsushi Yoshizawa
- Department of Frontier Materials Chemistry
- Graduate School of Science and Technology, Hirosaki University
- Aomori 036-8561
- Japan
| | - Misaki Kurata
- Department of Frontier Materials Chemistry
- Graduate School of Science and Technology, Hirosaki University
- Aomori 036-8561
- Japan
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16
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Sasaki H, Takanishi Y, Yamamoto J, Yoshizawa A. Photo-Driven Chirality Switching in a Dark Conglomerate Phase of an Achiral Liquid Crystal Trimer. ChemistrySelect 2018. [DOI: 10.1002/slct.201800067] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Haruna Sasaki
- Department of Frontier Materials Chemistry; Graduate School of Science and Technology; Hirosaki University; 3 Bunkyo-cho Hirosaki 036-8561 Japan
| | - Yoichi Takanishi
- Department of Physics; Graduate School of Science; Kyoto University; Oiwake-cho, Kitashirakawa, Sakyo-ku Kyoto 606-8502 Japan
| | - Jun Yamamoto
- Department of Physics; Graduate School of Science; Kyoto University; Oiwake-cho, Kitashirakawa, Sakyo-ku Kyoto 606-8502 Japan
| | - Atsushi Yoshizawa
- Department of Frontier Materials Chemistry; Graduate School of Science and Technology; Hirosaki University; 3 Bunkyo-cho Hirosaki 036-8561 Japan
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17
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Torgova S, Sreenilayam SP, Panarin YP, Francescangeli O, Vita F, Vij JK, Pozhidaev E, Minchenko M, Ferrero C, Strigazzi A. Short bent-core molecules: X-ray, polarization, dielectricity, texture and electro-optics investigations. Phys Chem Chem Phys 2017; 19:22946-22956. [PMID: 28813044 DOI: 10.1039/c7cp03561f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Bent-core liquid crystals based on 1,2,4-oxadiazole as a central unit have been the first mesogens to exhibit a ferroelectric response in the nematic phase. This behavior has been widely recognized as due to the presence of smectic-like polar cybotactic clusters permeating the nematic phase. Unfortunately, these compounds exhibited rather high melting points, about 120 °C, due to the presence of four benzene rings in the molecules. Here we describe the synthesis and physical characterization of a new series of BC mesogens, featuring the same bent core as the previous compounds but shorter outer substituents. By keeping only two benzene rings, we were able to lower the melting points to about 70 °C. However, while X-ray diffraction and dielectric spectroscopy measurements confirm the cybotactic nature of the nematic phase of these compounds, polarization and electro-optical measurements ascribe their polar response to flexoelectricity rather than to spontaneous polarization. Finally, texture investigation suggests the biaxiality of the nematic phase, which is indicated also by conoscopic measurements. These results are important for recognizing size and rigidity limitations in designing bent-core liquid crystal molecules suitable for applications.
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Affiliation(s)
- S Torgova
- P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Pr. 53, Moscow, 119991, Russia
| | - S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland
| | - Yu P Panarin
- Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland and School of Electrical and Electronic Engineering, Dublin Institute of Technology, Dublin, Ireland
| | - O Francescangeli
- Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio and CNISM, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - F Vita
- Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio and CNISM, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland
| | - E Pozhidaev
- P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Pr. 53, Moscow, 119991, Russia
| | - M Minchenko
- P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky Pr. 53, Moscow, 119991, Russia
| | - C Ferrero
- European Synchrotron Radiation Facility, Bôite Postale 220, 38043 Grenoble Cedex, France
| | - A Strigazzi
- Department of Applied Science and Technology, Physics Institute of Condensed Matter and Complex Systems, CNISM, Politecnico di Torino, Torino, Italy. and National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia
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18
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Alaasar M, Prehm M, Poppe S, Tschierske C. Development of Polar Order by Liquid‐Crystal Self‐Assembly of Weakly Bent Molecules. Chemistry 2017; 23:5541-5556. [DOI: 10.1002/chem.201606035] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Indexed: 01/23/2023]
Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry Martin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
- Department of Chemistry Faculty of Science Cairo University Giza Egypt
| | - Marko Prehm
- Institute of Chemistry Martin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
| | - Silvio Poppe
- Institute of Chemistry Martin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
| | - Carsten Tschierske
- Institute of Chemistry Martin Luther University Halle-Wittenberg Kurt Mothes Str. 2 06120 Halle (Saale) Germany
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19
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Kohout M, Alaasar M, Poryvai A, Novotná V, Poppe S, Tschierske C, Svoboda J. Photosensitive bent-core liquid crystals based on methyl substituted 3-hydroxybenzoic acid. RSC Adv 2017. [DOI: 10.1039/c7ra05632j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Photosensitive liquid crystals are of contemporary interest not only from the scientific point of view but also for various applications. The chemical structure of materials is used to tune their mesomorphic and photosensitive properties.
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Affiliation(s)
- Michal Kohout
- Department of Organic Chemistry
- University of Chemistry and Technology Prague
- 166 28 Prague 6
- Czech Republic
| | - Mohamed Alaasar
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- Halle-Saale
- Germany
- Department of Chemistry
| | - Anna Poryvai
- Department of Organic Chemistry
- University of Chemistry and Technology Prague
- 166 28 Prague 6
- Czech Republic
| | - Vladimíra Novotná
- Institute of Physics
- Academy of Science of the Czech Republic
- 182 21 Prague 9
- Czech Republic
| | - Silvio Poppe
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- Halle-Saale
- Germany
| | - Carsten Tschierske
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- Halle-Saale
- Germany
| | - Jiří Svoboda
- Department of Organic Chemistry
- University of Chemistry and Technology Prague
- 166 28 Prague 6
- Czech Republic
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20
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Sebastián N, Belau S, Eremin A, Alaasar M, Prehm M, Tschierske C. Emergence of polar order and tilt in terephthalate based bent-core liquid crystals. Phys Chem Chem Phys 2017; 19:5895-5905. [DOI: 10.1039/c6cp08145b] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The shown compound forms ferroelectric domains in a SmA phase, which adopt antipolar correlations before condensing into a weakly tilted antiferroelectric smectic phase.
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Affiliation(s)
- Nerea Sebastián
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - Sebastian Belau
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - Alexey Eremin
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - Mohamed Alaasar
- Institute of Chemistry
- Organic Chemistry
- Martin Luther University Halle-Wittenberg
- 06120 Halle/Saale
- Germany
| | - Marko Prehm
- Institute of Chemistry
- Organic Chemistry
- Martin Luther University Halle-Wittenberg
- 06120 Halle/Saale
- Germany
| | - Carsten Tschierske
- Institute of Chemistry
- Organic Chemistry
- Martin Luther University Halle-Wittenberg
- 06120 Halle/Saale
- Germany
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21
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Ocak H, Poppe M, Bilgin-Eran B, Karanlık G, Prehm M, Tschierske C. Effects of molecular chirality on self-assembly and switching in liquid crystals at the cross-over between rod-like and bent shapes. SOFT MATTER 2016; 12:7405-7422. [PMID: 27510177 DOI: 10.1039/c6sm00960c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A bent-core compound derived from a 4-cyanoresorcinol core unit with two terephthalate based rod-like wings and carrying chiral 3,7-dimethyloctyloxy side chains has been synthesized in racemic and enantiomerically pure form and characterized by polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical investigations to study the influence of molecular chirality on the superstructural chirality and polar order in lamellar liquid crystalline phases. Herein we demonstrate that the coupling of molecular chirality with superstructural layer chirality in SmCsPF domain phases (forming energetically distinct diastereomeric pairs) can fix the tilt direction and thus stabilize synpolar order, leading to bistable ferroelectric switching in the SmC* phases of the (S)-enantiomer, whereas tristable modes determine the switching of the racemate. Moreover, the mechanism of electric field induced molecular reorganization changes from a rotation around the molecular long axis in the racemate to a rotation on the tilt-cone for the (S)-enantiomer. At high temperature the enantiomer behaves like a rod-like molecule with a chirality induced ferroelectric SmC* phase and an electroclinic effect in the SmA'* phase. At reduced temperature sterically induced polarization, due to the bent molecular shape, becomes dominating, leading to much higher polarization values, thus providing access to high polarization ferroelectric materials with weakly bent compounds having only "weakly chiral" stereogenic units. Moreover, the field induced alignment of the SmCsPF(()*()) domains gives rise to a special kind of electroclinic effect appearing even in the absence of molecular chirality. Comparison with related compounds indicates that the strongest effects of chirality appear for weakly bent molecules with a relatively short coherence length of polar order, whereas for smectic phases with long range polar order the effects of the interlayer interfaces can override the chirality effects.
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Affiliation(s)
- Hale Ocak
- Institute of Chemistry, Organic Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 2, D-06120 Halle, Germany.
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22
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Yoshizawa A, Kato Y, Sasaki H, Takanishi Y, Yamamoto J. Optically Isotropic Homochiral Structure Produced by Intercalation of Achiral Liquid Crystal Trimers. J Phys Chem B 2016; 120:4843-51. [DOI: 10.1021/acs.jpcb.6b01242] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Atsushi Yoshizawa
- Department
of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
| | - Yusuke Kato
- Department
of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
| | - Haruna Sasaki
- Department
of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
| | - Yoichi Takanishi
- Department
of Physics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa,
Sakyo-ku, Kyoto, 606-8562, Japan
| | - Jun Yamamoto
- Department
of Physics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa,
Sakyo-ku, Kyoto, 606-8562, Japan
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23
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Sreenilayam SP, Panarin YP, Vij JK, Panov VP, Lehmann A, Poppe M, Prehm M, Tschierske C. Spontaneous helix formation in non-chiral bent-core liquid crystals with fast linear electro-optic effect. Nat Commun 2016; 7:11369. [PMID: 27156514 PMCID: PMC4865739 DOI: 10.1038/ncomms11369] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 03/21/2016] [Indexed: 01/31/2023] Open
Abstract
Liquid crystals (LCs) represent one of the foundations of modern communication and photonic technologies. Present display technologies are based mainly on nematic LCs, which suffer from limited response time for use in active colour sequential displays and limited image grey scale. Herein we report the first observation of a spontaneously formed helix in a polar tilted smectic LC phase (SmC phase) of achiral bent-core (BC) molecules with the axis of helix lying parallel to the layer normal and a pitch much shorter than the optical wavelength. This new phase shows fast (∼30 μs) grey-scale switching due to the deformation of the helix by the electric field. Even more importantly, defect-free alignment is easily achieved for the first time for a BC mesogen, thus providing potential use in large-scale devices with fast linear and thresholdless electro-optical response. Liquid crystals that consist of rod-like molecules currently dominate the materials used in industry for display and photonic applications. Here, the authors demonstrate electro-optic grey-scale switching based on the spontaneous formation of a short-pitch helix in a tilted smectic phase of achiral bent-core molecules.
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Affiliation(s)
- Sithara P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - Yuri P Panarin
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland.,School of Electrical and Electronic Engineering, Dublin Institute of Technology, Dublin 8, Ireland
| | - Jagdish K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - Vitaly P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - Anne Lehmann
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany
| | - Marco Poppe
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany
| | - Marko Prehm
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany
| | - Carsten Tschierske
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06120 Halle, Germany
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24
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Westphal E, Gallardo H, Caramori GF, Sebastián N, Tamba MG, Eremin A, Kawauchi S, Prehm M, Tschierske C. Polar Order and Symmetry Breaking at the Boundary between Bent-Core and Rodlike Molecular Forms: When 4-Cyanoresorcinol Meets the Carbosilane End Group. Chemistry 2016; 22:8181-97. [DOI: 10.1002/chem.201503901] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Indexed: 12/21/2022]
Affiliation(s)
- Eduard Westphal
- Institute of Chemistry, Organic Chemistry; Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 2; 06120 Halle/Saale Germany
- Department of Chemistry; Federal University of Santa Catarina; 88040-900 Florianópolis Brazil
| | - Hugo Gallardo
- Department of Chemistry; Federal University of Santa Catarina; 88040-900 Florianópolis Brazil
| | | | - Nerea Sebastián
- Department of Nonlinear Phenomena, Institute for Experimental Physics; Otto von Guericke University Magdeburg, Universitätsplatz 2; 39106 Magdeburg Germany
| | - Maria-Gabriela Tamba
- Department of Nonlinear Phenomena, Institute for Experimental Physics; Otto von Guericke University Magdeburg, Universitätsplatz 2; 39106 Magdeburg Germany
| | - Alexey Eremin
- Department of Nonlinear Phenomena, Institute for Experimental Physics; Otto von Guericke University Magdeburg, Universitätsplatz 2; 39106 Magdeburg Germany
| | - Susumu Kawauchi
- Department of Organic & Polymeric Materials; Tokyo Institute of Technology, O-okayama, Meguro-ku; Tokyo 152-8552 Japan
| | - Marko Prehm
- Institute of Chemistry, Organic Chemistry; Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 2; 06120 Halle/Saale Germany
| | - Carsten Tschierske
- Institute of Chemistry, Organic Chemistry; Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 2; 06120 Halle/Saale Germany
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25
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Alaasar M, Prehm M, Tschierske C. Helical Nano-crystallite (HNC) Phases: Chirality Synchronization of Achiral Bent-Core Mesogens in a New Type of Dark Conglomerates. Chemistry 2016; 22:6583-97. [DOI: 10.1002/chem.201505016] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry; Martin Luther University Halle-Wittenberg; Kurt Mothes Str. 2 06120 Halle (Saale) Germany), Fax
- Department of Chemistry; Faculty of Science; Cairo University; Giza Egypt
| | - Marko Prehm
- Institute of Chemistry; Martin Luther University Halle-Wittenberg; Kurt Mothes Str. 2 06120 Halle (Saale) Germany), Fax
| | - Carsten Tschierske
- Institute of Chemistry; Martin Luther University Halle-Wittenberg; Kurt Mothes Str. 2 06120 Halle (Saale) Germany), Fax
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26
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Alaasar M, Prehm M, Cao Y, Liu F, Tschierske C. Spontaneous Mirror-Symmetry Breaking in Isotropic Liquid Phases of Photoisomerizable Achiral Molecules. Angew Chem Int Ed Engl 2016; 55:312-6. [PMID: 26490058 DOI: 10.1002/anie.201508097] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Indexed: 11/07/2022]
Abstract
Spontaneous mirror-symmetry breaking is of fundamental importance in science as it contributes to the development of chiral superstructures and new materials and has a major impact on the discussion around the emergence of uniform chirality in biological systems. Herein we report chirality synchronization, leading to spontaneous chiral conglomerate formation in isotropic liquids of achiral and photoisomerizable azobenzene-based rod-like molecules. The position of fluorine substituents at the aromatic core is found to have a significant effect on the stability and the temperature range of these chiral liquids. Moreover, these liquid conglomerates occur in a new phase sequence adjacent to a 3D tetragonal mesophase.
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Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes Str. 2, 06120 Halle/Saale (Germany). .,Department of Chemistry, Faculty of Science, Cairo University, P.O. 12613 Giza (Egypt).
| | - Marko Prehm
- Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes Str. 2, 06120 Halle/Saale (Germany)
| | - Yu Cao
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (P. R. China)
| | - Feng Liu
- State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049 (P. R. China).
| | - Carsten Tschierske
- Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes Str. 2, 06120 Halle/Saale (Germany).
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27
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Alaasar M, Prehm M, Tschierske C. Mirror symmetry breaking in fluorinated bent-core mesogens. RSC Adv 2016. [DOI: 10.1039/c6ra18482k] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
New fluorinated bent-core liquid crystals exhibiting helical nano-crystallite phases composed of chiral domains with opposite handedness and polar smcetic phases.
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Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- D-06120 Halle (Saale)
- Germany
- Department of Chemistry
| | - Marko Prehm
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- D-06120 Halle (Saale)
- Germany
| | - Carsten Tschierske
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- D-06120 Halle (Saale)
- Germany
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28
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Alaasar M, Poppe S, Dong Q, Liu F, Tschierske C. Mirror symmetry breaking in cubic phases and isotropic liquids driven by hydrogen bonding. Chem Commun (Camb) 2016; 52:13869-13872. [DOI: 10.1039/c6cc08226b] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Achiral hydrogen bonded rod-like complexes with four nonequally distributed terminal alkyl chains form a chirality synchronized isotropic liquid conglomerate as well as a conglomerate type chiral cubic phase.
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Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- D-06120 Halle
- Germany
- Department of Chemistry
| | - Silvio Poppe
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- D-06120 Halle
- Germany
| | - Qingshu Dong
- State Key Laboratory for Mechanical Behavior of Materials
- Xi’an Jiaotong University
- Xi’an 710049
- P. R. China
| | - Feng Liu
- State Key Laboratory for Mechanical Behavior of Materials
- Xi’an Jiaotong University
- Xi’an 710049
- P. R. China
| | - Carsten Tschierske
- Institute of Chemistry
- Martin Luther University Halle-Wittenberg
- D-06120 Halle
- Germany
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29
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Yoshizawa A, Kato Y, Sasaki H, Takanishi Y, Yamamoto J. Chiral conglomerates observed for a binary mixture of a nematic liquid crystal trimer and 6OCB. SOFT MATTER 2015; 11:8827-8833. [PMID: 26395546 DOI: 10.1039/c5sm02121a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Dark conglomerates of domains with opposite handedness, which are designated as dark conglomerate phases (DC phases), have attracted much attention. After designing an achiral liquid crystal trimer, 4,4′-bis{7-[4-(5-octyloxypyrimidin-2-yl)phenyloxy]heptyloxy}biphenyl (1), which exhibits only a nematic phase, we prepared binary mixtures with some typical rod-like nematic liquid crystals, i.e., 4′-hexyloxy-4-cyanobiphenyl (6OCB), 2-(4-hexyloxyphenyl)-5-pentyloxypyrimidine (PPY), or 4-methyloxyphenyl 4-hexyloxycyclohexanecarboxylate (PCA), and investigated their phase transition behaviour. The binary mixtures containing 55–90 mol% of 6OCB were found to exhibit a nematic phase and a DC phase of chiral domains with opposite handedness. However, neither PPY nor PCA induced such a chiral conglomerate phase in the mixture with trimer 1. We discuss how core–core interactions contribute to produce such a chiral conglomerate phase.
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Affiliation(s)
- Atsushi Yoshizawa
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan.
| | - Yusuke Kato
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan.
| | - Haruna Sasaki
- Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan.
| | - Yoichi Takanishi
- Department of Physics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto, 606-8562, Japan
| | - Jun Yamamoto
- Department of Physics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto, 606-8562, Japan
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30
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Alaasar M, Prehm M, Tamba MG, Sebastián N, Eremin A, Tschierske C. Development of Polar Order in the Liquid Crystal Phases of a 4-Cyanoresorcinol-Based Bent-Core Mesogen with Fluorinated Azobenzene Wings. Chemphyschem 2015; 17:278-87. [DOI: 10.1002/cphc.201500891] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 01/17/2023]
Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry, Organic Chemistry; Martin Luther University Halle-Wittenberg; Kurt-Mothes Str. 2 06120 Halle/Saale Germany
- Department of Chemistry; Faculty of Science; Cairo University; Giza Egypt
| | - Marko Prehm
- Institute of Chemistry, Organic Chemistry; Martin Luther University Halle-Wittenberg; Kurt-Mothes Str. 2 06120 Halle/Saale Germany
| | - Maria-Gabriela Tamba
- Institute for Experimental Physics; Otto-von-Guericke University Magdeburg; Universitätsplatz 2 39106 Magdeburg Germany
| | - Nerea Sebastián
- Institute for Experimental Physics; Otto-von-Guericke University Magdeburg; Universitätsplatz 2 39106 Magdeburg Germany
| | - Alexey Eremin
- Institute for Experimental Physics; Otto-von-Guericke University Magdeburg; Universitätsplatz 2 39106 Magdeburg Germany
| | - Carsten Tschierske
- Institute of Chemistry, Organic Chemistry; Martin Luther University Halle-Wittenberg; Kurt-Mothes Str. 2 06120 Halle/Saale Germany
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31
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Alaasar M, Prehm M, Cao Y, Liu F, Tschierske C. Spontaneous Mirror-Symmetry Breaking in Isotropic Liquid Phases of Photoisomerizable Achiral Molecules. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201508097] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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Sasaki H, Takanishi Y, Yamamoto J, Yoshizawa A. Supermolecular Bent Configuration Composed of Achiral Flexible Liquid Crystal Trimers Exhibiting Chiral Domains with Opposite Handedness. J Phys Chem B 2015; 119:4531-8. [DOI: 10.1021/jp512710r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Haruna Sasaki
- Department
of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, 036-8561, Japan
| | - Yoichi Takanishi
- Department
of Physics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa,
Sakyo-ku, Kyoto, 605-8502, Japan
| | - Jun Yamamoto
- Department
of Physics, Graduate School of Science, Kyoto University, Oiwake-cho, Kitashirakawa,
Sakyo-ku, Kyoto, 605-8502, Japan
| | - Atsushi Yoshizawa
- Department
of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, 036-8561, Japan
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33
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Ocak H, Bilgin-Eran B, Güzeller D, Prehm M, Tschierske C. Twist grain boundary (TGB) states of chiral liquid crystalline bent-core mesogens. Chem Commun (Camb) 2015; 51:7512-5. [PMID: 25834996 DOI: 10.1039/c5cc01592h] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chiral 4-cyanoresorcinol derived bent-core molecules form liquid crystalline phases with helically deformed layers representing TGBA and TGBC-like structures.
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Affiliation(s)
- Hale Ocak
- Institute of Chemistry
- Organic Chemistry
- Martin-Luther University Halle-Wittenberg
- 06120 Halle
- Germany
| | - Belkız Bilgin-Eran
- Department of Chemistry
- Yildiz Technical University
- Davutpasa Yerlesim Birimi
- Esenler
- Turkey
| | - Dilek Güzeller
- Department of Chemistry
- Yildiz Technical University
- Davutpasa Yerlesim Birimi
- Esenler
- Turkey
| | - Marko Prehm
- Institute of Chemistry
- Organic Chemistry
- Martin-Luther University Halle-Wittenberg
- 06120 Halle
- Germany
| | - Carsten Tschierske
- Institute of Chemistry
- Organic Chemistry
- Martin-Luther University Halle-Wittenberg
- 06120 Halle
- Germany
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34
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Angelova A, Angelov B, Mutafchieva R, Lesieur S. Biocompatible Mesoporous and Soft Nanoarchitectures. J Inorg Organomet Polym Mater 2014. [DOI: 10.1007/s10904-014-0143-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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35
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Alaasar M, Prehm M, Brautzsch M, Tschierske C. Dark conglomerate phases of azobenzene derived bent-core mesogens - relationships between the molecular structure and mirror symmetry breaking in soft matter. SOFT MATTER 2014; 10:7285-7296. [PMID: 25095778 DOI: 10.1039/c4sm01255k] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
New 4-bromoresorcinol based bent-core molecules with peripheral fluoro substituted azobenzene wings have been synthesized and the liquid crystalline self-assembly was investigated by differential scanning calorimetry (DSC), optical polarizing microscopy (POM), electro-optic studies and X-ray diffraction (XRD). A new type of optically isotropic mesophase composed of chiral domains with opposite handedness (dark conglomerate phases, DC phases) is observed, which for some homologues with medium alkyl chain length is stable down to ambient temperature. It is proposed that these DC phases are formed by helical twisted nano-domains of limited size and composed of the crystallized aromatic cores which are separated by the disordered alkyl chains. This structure is distinct from the previously known soft helical nano-filament phases (HNF phases, B4 phases) formed by extended crystalline nano-filaments and also distinct from the fluid sponge phases composed of deformed fluid layers. Comparison with related bent-core molecules having H, F, Cl, I, CH3 and CN groups in the 4-position at the resorcinol core, either with or without additional peripheral fluorines, provided information about the effects of these substituents on the tendency to form DC phases. Based on these relationships and by comparison with the minimum energy conformations obtained by DFT calculations a hypothesis is provided for the formation of DC phases depending on the molecular structure.
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Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt Mothes Str. 2, D-06120 Halle (Saale), Germany.
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36
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Dressel C, Liu F, Prehm M, Zeng X, Ungar G, Tschierske C. Dynamic Mirror-Symmetry Breaking in Bicontinuous Cubic Phases. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406907] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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37
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Dressel C, Liu F, Prehm M, Zeng X, Ungar G, Tschierske C. Dynamic mirror-symmetry breaking in bicontinuous cubic phases. Angew Chem Int Ed Engl 2014; 53:13115-20. [PMID: 25257551 PMCID: PMC4501316 DOI: 10.1002/anie.201406907] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Indexed: 11/11/2022]
Abstract
Chiral segregation of enantiomers or chiral conformers of achiral molecules during self-assembly in well-ordered crystalline superstructures has fascinated chemists since Pasteur. Here we report spontaneous mirror-symmetry breaking in cubic phases formed by achiral multichain-terminated diphenyl-2,2'-bithiophenes. It was found that stochastic symmetry breaking is a general phenomenon observed in bicontinuous cubic liquid crystal phases of achiral rod-like compounds. In all compounds studied the Im3̄m cubic phase is always chiral, while the Ia3̄d phase is achiral. These intriguing observations are explained by propagation of homochiral helical twist across the entire networks through helix matching at network junctions. In the Ia3̄d phase the opposing chiralities of the two networks cancel, but not so in the three-networks Im3̄m phase. The high twist in the Im3̄m phase explains its previously unrecognized chirality, as well as the origin of this complex structure and the transitions between the different cubic phases.
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Affiliation(s)
- Christian Dressel
- Institute of Chemistry, Organic Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Str. 2, 06120 Halle (Germany)
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38
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Dressel C, Reppe T, Prehm M, Brautzsch M, Tschierske C. Chiral self-sorting and amplification in isotropic liquids of achiral molecules. Nat Chem 2014; 6:971-7. [DOI: 10.1038/nchem.2039] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 07/23/2014] [Indexed: 01/30/2023]
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39
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Alaasar M, Prehm M, Poppe M, Nagaraj M, Vij JK, Tschierske C. Development of polar order and tilt in lamellar liquid crystalline phases of a bent-core mesogen. SOFT MATTER 2014; 10:5003-5016. [PMID: 24894807 DOI: 10.1039/c4sm00593g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A new bent-core mesogen combining a 4-cyanoresorcinol unit with two terephthalate based rod-like wings and terminated by two long alkyl chains, was synthesized and investigated by DSC, XRD, optical, electrooptical and dielectric methods. A series of liquid crystalline phases in the unique sequence SmA-SmA(P)-SmCPR-(M1/SmCPα)-SmCsPA-SmCPA-SmCaPA, mainly distinguished by the degree and mode of correlation of tilt and polar order, was observed. The development of polar order is associated with the emergence of a small tilt (<10°). With decreasing temperature the tilt changes from random (SmA) via synclinic to anticlinic, while the coherence length of the polar domains grows. This small tilt gives rise to an only weak layer coupling which is in competition with the polar coupling and this leads to new modes of self assembly in lamellar phases of bent-core mesogens, among them the SmCPR and the SmCPα phases. The SmCPR phase is an only slightly tilted biaxial smectic phase with randomized polar order and the SmCPα phase is a slightly tilted and antiferroelectric switching, but uniaxial smectic phase. For this phase a regular change of the in-plane polarization vector between the layers by an angle between >0° and <90° is proposed.
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Affiliation(s)
- Mohamed Alaasar
- Institute of Chemistry, Martin Luther University Halle-Wittenberg, Kurt Mothes Str. 2, D-06120 Halle (Saale), Germany.
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40
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Affiliation(s)
- Wen Li
- State Key Laboratory of Supramolecular Structure and Materials; Jilin University; Changchun 130012 China
| | - Lixin Wu
- State Key Laboratory of Supramolecular Structure and Materials; Jilin University; Changchun 130012 China
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41
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1,2,4-Oxadiazole-Based Bent-Core Liquid Crystals with Cybotactic Nematic Phases. Chemphyschem 2014; 15:1323-35. [DOI: 10.1002/cphc.201301070] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Indexed: 11/07/2022]
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42
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Gimeno N, Pintre I, Martínez-Abadía M, Serrano JL, Ros MB. Bent-core liquid crystal phases promoted by azo-containing molecules: from monomers to side-chain polymers. RSC Adv 2014. [DOI: 10.1039/c4ra02079k] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In situ photopolymerization or ATRP in solution provide azo-containing polymers showing room temperature SmCPg arrangements and broad ranges of SmCP mesophase.
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Affiliation(s)
- Nélida Gimeno
- Instituto de Ciencia de Materiales de Aragón
- Universidad de Zaragoza-CSIC
- Departamento de Química Orgánica
- Facultad de Ciencias
- 50009 Zaragoza, Spain
| | - Inmaculada Pintre
- Instituto de Ciencia de Materiales de Aragón
- Universidad de Zaragoza-CSIC
- Departamento de Química Orgánica
- Facultad de Ciencias
- 50009 Zaragoza, Spain
| | - Marta Martínez-Abadía
- Instituto de Ciencia de Materiales de Aragón
- Universidad de Zaragoza-CSIC
- Departamento de Química Orgánica
- Facultad de Ciencias
- 50009 Zaragoza, Spain
| | - José Luis Serrano
- Instituto de Nanociencia de Aragón
- Universidad de Zaragoza
- Departamento de Química Orgánica
- Facultad de Ciencias
- 50009 Zaragoza, Spain
| | - M. Blanca Ros
- Instituto de Ciencia de Materiales de Aragón
- Universidad de Zaragoza-CSIC
- Departamento de Química Orgánica
- Facultad de Ciencias
- 50009 Zaragoza, Spain
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43
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Tschierske C. Entwicklung struktureller Komplexität durch Selbstorganisation in flüssigkristallinen Systemen. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201300872] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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44
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Tschierske C. Development of structural complexity by liquid-crystal self-assembly. Angew Chem Int Ed Engl 2013; 52:8828-78. [PMID: 23934786 DOI: 10.1002/anie.201300872] [Citation(s) in RCA: 354] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Indexed: 11/09/2022]
Abstract
Since the discovery of the liquid-crystalline state of matter 125 years ago, this field has developed into a scientific area with many facets. This Review presents recent developments in the molecular design and self-assembly of liquid crystals. The focus is on new exciting soft-matter structures distinct from the usually observed nematic, smectic, and columnar phases. These new structures have enhanced complexity, including multicompartment and cellular structures, periodic and quasiperiodic arrays of spheres, and new emergent properties, such as ferroelctricity and spontaneous achiral symmetry-breaking. Comparisons are made with developments in related fields, such as self-assembled monolayers, multiblock copolymers, and nanoparticle arrays. Measures of structural complexity used herein are the size of the lattice, the number of distinct compartments, the dimensionality, and the logic depth of the resulting supramolecular structures.
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Affiliation(s)
- Carsten Tschierske
- Institut für Chemie, Organische Chemie, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle Saale, Germany.
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Alaasar M, Prehm M, Tschierske C. A new room temperature dark conglomerate mesophase formed by bent-core molecules combining 4-iodoresorcinol with azobenzene units. Chem Commun (Camb) 2013; 49:11062-4. [DOI: 10.1039/c3cc45938a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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