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Kolmangadi MA, Wani YM, Schönhals A, Nikoubashman A. Coarse-Grained Simulations of Columnar Ionic Liquid Crystals: Comparison with Experiments. J Phys Chem B 2024; 128:8215-8222. [PMID: 39163525 DOI: 10.1021/acs.jpcb.4c03041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/22/2024]
Abstract
We simulate a homologous series of guanidinium-based columnar ionic liquid crystals (ILCs) using coarse-grained molecular dynamics (MD) simulations with the Martini force field. We systematically vary the length of alkyl side chains, ILC-n (n = 8, 12, 16), and compare our results with previous experimental findings. Experimentally, ILC-8 exhibits a narrow mesophase window and weak columnar order, while ILC-12 and ILC-16 display a broad mesophase window and high columnar order. The MD simulations show that ILC-8 forms a percolated structure, whereas the longer chain analogues self-assemble into columns, with columnar assembly becoming more prominent as the side chain length increases, in qualitative agreement with the experiments. Furthermore, the intercolumnar distance increases monotonically with increasing side chain length and decreases with increasing temperature. Finally, we find that the diffusion coefficient and ionic conductivity decrease substantially with increasing chain length, consistent with experimental observations. We attribute this decrease in mobility to the formation of hexagonally ordered columns, which restrict transport more than percolated networks.
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Affiliation(s)
- Mohamed A Kolmangadi
- Bundesantalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Yashraj M Wani
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Andreas Schönhals
- Bundesantalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
- Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Arash Nikoubashman
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, 01069 Dresden, Germany
- Institut für Theoretische Physik, Technische Universität Dresden, 01069 Dresden, Germany
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Li Z, Raab A, Kolmangadi MA, Busch M, Grunwald M, Demel F, Bertram F, Kityk AV, Schönhals A, Laschat S, Huber P. Self-Assembly of Ionic Superdiscs in Nanopores. ACS NANO 2024; 18:14414-14426. [PMID: 38760015 PMCID: PMC11155240 DOI: 10.1021/acsnano.4c01062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 04/23/2024] [Accepted: 05/01/2024] [Indexed: 05/19/2024]
Abstract
Discotic ionic liquid crystals (DILCs) consist of self-assembled superdiscs of cations and anions that spontaneously stack in linear columns with high one-dimensional ionic and electronic charge mobility, making them prominent model systems for functional soft matter. Compared to classical nonionic discotic liquid crystals, many liquid crystalline structures with a combination of electronic and ionic conductivity have been reported, which are of interest for separation membranes, artificial ion/proton conducting membranes, and optoelectronics. Unfortunately, a homogeneous alignment of the DILCs on the macroscale is often not achievable, which significantly limits the applicability of DILCs. Infiltration into nanoporous solid scaffolds can, in principle, overcome this drawback. However, due to the experimental challenges to scrutinize liquid crystalline order in extreme spatial confinement, little is known about the structures of DILCs in nanopores. Here, we present temperature-dependent high-resolution optical birefringence measurement and 3D reciprocal space mapping based on synchrotron X-ray scattering to investigate the thermotropic phase behavior of dopamine-based ionic liquid crystals confined in cylindrical channels of 180 nm diameter in macroscopic anodic aluminum oxide membranes. As a function of the membranes' hydrophilicity and thus the molecular anchoring to the pore walls (edge-on or face-on) and the variation of the hydrophilic-hydrophobic balance between the aromatic cores and the alkyl side chain motifs of the superdiscs by tailored chemical synthesis, we find a particularly rich phase behavior, which is not present in the bulk state. It is governed by a complex interplay of liquid crystalline elastic energies (bending and splay deformations), polar interactions, and pure geometric confinement and includes textural transitions between radial and axial alignment of the columns with respect to the long nanochannel axis. Furthermore, confinement-induced continuous order formation is observed in contrast to discontinuous first-order phase transitions, which can be quantitatively described by Landau-de Gennes free energy models for liquid crystalline order transitions in confinement. Our observations suggest that the infiltration of DILCs into nanoporous solids allows tailoring their nanoscale texture and ion channel formation and thus their electrical and optical functionalities over an even wider range than in the bulk state in a homogeneous manner on the centimeter scale as controlled by the monolithic nanoporous scaffolds.
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Affiliation(s)
- Zhuoqing Li
- Institute
for Materials and X-ray Physics, Hamburg
University of Technology, Denickestr. 15, 21073 Hamburg, Germany
- Centre
for X-ray and Nano Science CXNS, Deutsches
Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Aileen Raab
- Institut
für Organische Chemie, Universität
Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Mohamed Aejaz Kolmangadi
- Bundesanstalt
für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
| | - Mark Busch
- Institute
for Materials and X-ray Physics, Hamburg
University of Technology, Denickestr. 15, 21073 Hamburg, Germany
- Centre
for X-ray and Nano Science CXNS, Deutsches
Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Marco Grunwald
- Institut
für Organische Chemie, Universität
Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Felix Demel
- Institut
für Organische Chemie, Universität
Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Florian Bertram
- Deutsches
Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
| | - Andriy V. Kityk
- Faculty of
Electrical Engineering, Czestochowa University
of Technology, Al. Armii
Krajowej 17, 42-200 Czestochowa, Poland
| | - Andreas Schönhals
- Bundesanstalt
für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany
- Institut
für Chemie, Technische Universität
Berlin, Straße des
17. Juni 135, 10623 Berlin, Germany
| | - Sabine Laschat
- Institut
für Organische Chemie, Universität
Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Patrick Huber
- Institute
for Materials and X-ray Physics, Hamburg
University of Technology, Denickestr. 15, 21073 Hamburg, Germany
- Centre
for X-ray and Nano Science CXNS, Deutsches
Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
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Łoś J, Drozd-Rzoska A, Rzoska S. Critical-like behavior of low-frequency dielectric properties in compressed liquid crystalline octyloxycyanobiphenyl (8OCB) and its nanocolloid with paraelectric BaTiO3. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
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Ishino K, Shingai H, Hikita Y, Yoshikawa I, Houjou H, Iwase K. Cold Crystallization and the Molecular Structure of Imidazolium-Based Ionic Liquid Crystals with a p-Nitroazobenzene Moiety. ACS OMEGA 2021; 6:32869-32878. [PMID: 34901637 PMCID: PMC8655916 DOI: 10.1021/acsomega.1c04866] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
The cold crystallization mechanism of 1-{[4'-(4″-nitrophenylazo)phenyloxy]}hexyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate ionic liquid crystal was investigated based on thermal analysis, structural analysis, infrared spectroscopy, and quantum chemical calculations. By conducting thorough structural characterization, we found that the prerequisite for cold crystallization is the irreversible molecular conformational alteration induced by the initial heating of the as-grown crystal into a smectic liquid crystal. The originally linear cation molecule bends and forms a step-stair conformation that persists throughout the subsequent heating and cooling processes as phase transition occurs from the crystal phase to the liquid crystal phase and then to the isotropic liquid phase. The formation of cold crystal occurs because of the choice of molecular stability over crystalline stability. Given the exothermic anomaly exhibited upon heating generic crystals to cold crystals, these findings demonstrate the promising potential of this ionic liquid crystal for thermal energy storage applications.
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Affiliation(s)
- Katsuma Ishino
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
| | - Hajime Shingai
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
| | - Yasuyuki Hikita
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
| | - Isao Yoshikawa
- Institute
of Industrial Science, The University of
Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Hirohiko Houjou
- Institute
of Industrial Science, The University of
Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
- Environmental
Science Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Katsunori Iwase
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
- Institute
of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-Ku, Nagoya, Aichi 464-8601, Japan
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