1
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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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2
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Longa L, Cieśla M, Karbowniczek P, Chrzanowska A. Conformational degrees of freedom and stability of splay-bend ordering in the limit of a very strong planar anchoring. Phys Rev E 2023; 107:034707. [PMID: 37073017 DOI: 10.1103/physreve.107.034707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 03/09/2023] [Indexed: 04/20/2023]
Abstract
We study the self-organization in a monolayer (a two-dimensional system) of flexible planar trimer particles. The molecules are made up of two mesogenic units linked by a spacer, all of which are modeled as hard needles of the same length. Each molecule can dynamically adopt two conformational states: an achiral bent-shaped (cis-) and a chiral zigzag (trans-) one. Using constant pressure Monte Carlo simulations and Onsager-type density functional theory (DFT), we show that the system consisting of these molecules exhibits a rich spectrum of liquid crystalline phases. The most interesting observation is the identification of stable smectic splay-bend (S_{SB}) and chiral smectic-A (S_{A}^{*}) phases. The S_{SB} phase is also stable in the limit, where only cis- conformers are allowed. The second phase that occupies a considerable portion of the phase diagram is S_{A}^{*} with chiral layers, where the chirality of the neighboring layers is of opposite sign. The study of the average fractions of the trans- and cis- conformers in various phases shows that while in the isotropic phase all fractions are equally populated, the S_{A}^{*} phase is dominated by chiral conformers (zigzag), but the achiral conformers win in the smectic splay-bend phase. To clarify the possibility of stabilization of the nematic splay-bend (N_{SB}) phase for trimers, the free energy of the N_{SB} and S_{SB} phases is calculated within DFT for the cis- conformers, for densities where simulations show stable S_{SB}. It turns out that the N_{SB} phase is unstable away from the phase transition to the nematic phase, and its free energy is always higher than that of S_{SB}, down to the transition to the nematic phase, although the difference in free energies becomes extremely small when approaching the transition.
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Affiliation(s)
- Lech Longa
- Marian Smoluchowski Institute of Physics, Department of Statistical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, ul. Łojasiewicza 11, 30-348 Kraków, Poland
| | - Michał Cieśla
- Marian Smoluchowski Institute of Physics, Department of Statistical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, ul. Łojasiewicza 11, 30-348 Kraków, Poland
| | - Paweł Karbowniczek
- Faculty of Materials Engineering and Physics, Cracow University of Technology, ul. Podchorążych 1, 30-084, Kraków, Poland
| | - Agnieszka Chrzanowska
- Faculty of Materials Engineering and Physics, Cracow University of Technology, ul. Podchorążych 1, 30-084, Kraków, Poland
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3
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Zhang XJ, Sun YW, Li ZW, Sun ZY. Transition kinetics of defect patterns in confined two-dimensional smectic liquid crystals. Phys Rev E 2021; 104:044704. [PMID: 34781539 DOI: 10.1103/physreve.104.044704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 10/04/2021] [Indexed: 01/21/2023]
Abstract
Topological defects in liquid crystals under confined geometries have attracted extensive research interests. Here, we perform molecular dynamics simulations to investigate the formation and transition of defect patterns in two-dimensional smectic Gay-Berne liquid crystals with a simple rectangular confinement boundary. Two typical types of defect patterns, bridge and diagonal defect patterns, are observed, which can be transformable continuously between each other over time. The transition usually starts from the line or point defect regions, and the competition between neighboring and opposite boundary effects induces the continuous realignments of the smectic layers to connect the neighboring or opposite walls. The relative stability of these two defect patterns can be controlled by changing the confinement conditions. These results deepen our understanding of transition kinetics of defect patterns in confined liquid crystals.
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Affiliation(s)
- Xiao-Jie Zhang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China and University of Science and Technology of China, Hefei 230026, China
| | - Yu-Wei Sun
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China and University of Science and Technology of China, Hefei 230026, China
| | - Zhan-Wei Li
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China and University of Science and Technology of China, Hefei 230026, China
| | - Zhao-Yan Sun
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China and University of Science and Technology of China, Hefei 230026, China
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4
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Kityk AV, Gor GY, Huber P. Adsorption from binary liquid solutions into mesoporous silica: a capacitance isotherm on 5CB nematogen/cyclohexane mixtures. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1909160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Andriy V. Kityk
- Institute for Materials and X-Ray Physics, Hamburg University of Technology, Hamburg, Germany
- Faculty of Electrical Engineering, Czestochowa University of Technology, Czestochowa, Poland
| | - Gennady Y. Gor
- Otto H. York Department Chemical and Materials Engineering, New Jersey Institute of Technology, University Heights, Newark, NJ, USA
| | - Patrick Huber
- Institute for Materials and X-Ray Physics, Hamburg University of Technology, Hamburg, Germany
- High-Resolution X-Ray Analytics of Materials Research Group, Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
- Centre for Hybrid Nanostructures CHyN, Hamburg University, Hamburg, Germany
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5
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Hare SM, Lunsford-Poe B, Kim M, Serra F. Chiral Liquid Crystal Lenses Confined in Microchannels. MATERIALS 2020; 13:ma13173761. [PMID: 32858819 PMCID: PMC7503803 DOI: 10.3390/ma13173761] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 08/17/2020] [Accepted: 08/19/2020] [Indexed: 11/16/2022]
Abstract
It is known that the liquid crystalline smectic-A phase has geometric defects, called focal conic domains, which can be used as gradient-index microlenses. Cholesteric (chiral nematic) phases also have topological defects with a central symmetry and a singularity at their center. We explore a weakly chiral system in which both types of defects can be present in the same material at different temperatures, and with this strategy we create lenses whose focal length is tunable with temperature. We measure the focal length of the tunable lenses, and we investigate the behavior of the defects near the phase transition. We identify the experimental conditions that make the simultaneous presence of the smectic focal conic domains and the circular cholesteric domains possible, such as the concentration of chiral dopant and the rate of heating and cooling. The transformation of focal conic domains into circular cholesteric domains is a new example of memory at the phase transition between smectic-A and nematic liquid crystals.
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6
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Skutnik RA, Geier IS, Schoen M. A biaxial nematic liquid crystal composed of matchbox-symmetric molecules. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1726520] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Robert A. Skutnik
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Immanuel S. Geier
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Martin Schoen
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
- Department of Chemical Engineering, Imperial College London, London, UK
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7
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Sentker K, Yildirim A, Lippmann M, Zantop AW, Bertram F, Hofmann T, Seeck OH, Kityk AV, Mazza MG, Schönhals A, Huber P. Self-assembly of liquid crystals in nanoporous solids for adaptive photonic metamaterials. NANOSCALE 2019; 11:23304-23317. [PMID: 31788679 DOI: 10.1039/c9nr07143a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nanoporous media exhibit structures significantly smaller than the wavelengths of visible light and can thus act as photonic metamaterials. Their optical functionality is not determined by the properties of the base materials, but rather by tailored, multiscale structures, in terms of precise pore shape, geometry, and orientation. Embedding liquid crystals in pore space provides additional opportunities to control light-matter interactions at the single-pore, meta-atomic scale. Here, we present temperature-dependent 3D reciprocal space mapping using synchrotron-based X-ray diffraction in combination with high-resolution birefringence experiments on disk-like mesogens (HAT6) imbibed in self-ordered arrays of parallel cylindrical pores 17 to 160 nm across in monolithic anodic aluminium oxide (AAO). In agreement with Monte Carlo computer simulations we observe a remarkably rich self-assembly behaviour, unknown from the bulk state. It encompasses transitions between the isotropic liquid state and discotic stacking in linear columns as well as circular concentric ring formation perpendicular and parallel to the pore axis. These textural transitions underpin an optical birefringence functionality, tuneable in magnitude and in sign from positive to negative via pore size, pore surface-grafting and temperature. Our study demonstrates that the advent of large-scale, self-organised nanoporosity in monolithic solids along with confinement-controllable phase behaviour of liquid-crystalline matter at the single-pore scale provides a reliable and accessible tool to design materials with adjustable optical anisotropy, and thus offers versatile pathways to fine-tune polarisation-dependent light propagation speeds in materials. Such a tailorability is at the core of the emerging field of transformative optics, allowing, e.g., adjustable light absorbers and extremely thin metalenses.
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Affiliation(s)
- Kathrin Sentker
- Institute of Materials Physics and Technology, Hamburg University of Technology, 21073 Hamburg, Germany.
| | - Arda Yildirim
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany
| | - Milena Lippmann
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Arne W Zantop
- Max-Planck-Institute for Dynamics and Self-Organization, Am Faßberg 17, D-37077 Göttingen, Germany
| | - Florian Bertram
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Tommy Hofmann
- Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Oliver H Seeck
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Andriy V Kityk
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland.
| | - Marco G Mazza
- Max-Planck-Institute for Dynamics and Self-Organization, Am Faßberg 17, D-37077 Göttingen, Germany and Interdisciplinary Centre for Mathematical Modelling and Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK
| | - Andreas Schönhals
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany
| | - Patrick Huber
- Institute of Materials Physics and Technology, Hamburg University of Technology, 21073 Hamburg, Germany.
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8
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Eichler JC, Skutnik RA, Sengupta A, Mazza MG, Schoen M. Emergent biaxiality in nematic microflows illuminated by a laser beam. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1663286] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Jan-Christoph Eichler
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Robert A. Skutnik
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
| | - Anupam Sengupta
- Physics and Materials Science Research Unit, University of Luxembourg, Luxembourg City, Grand Duchy of Luxembourg
| | - Marco G. Mazza
- Interdisciplinary Centre for Mathematical Modelling and Department of Mathematical Sciences, Loughborough University, Loughborough, UK
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Göttingen, Germany
| | - Martin Schoen
- Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Berlin, Germany
- Department of Chemical Engineering, Imperial College London, London, UK
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9
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Nozawa T, Brumby PE, Ayuba S, Yasuoka K. Ordering in clusters of uniaxial anisotropic particles during homogeneous nucleation and growth. J Chem Phys 2019; 150:054903. [PMID: 30736692 DOI: 10.1063/1.5064410] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Takuma Nozawa
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Paul E. Brumby
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Sho Ayuba
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Kenji Yasuoka
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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10
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Nozawa T, Brumby PE, Yasuoka K. Effect of Central Longitudinal Dipole Interactions on Chiral Liquid-Crystal Phases. Int J Mol Sci 2018; 19:ijms19092715. [PMID: 30208651 PMCID: PMC6164681 DOI: 10.3390/ijms19092715] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 09/05/2018] [Accepted: 09/06/2018] [Indexed: 12/03/2022] Open
Abstract
Monte Carlo simulations of chiral liquid-crystals, represented by a simple coarse-grained chiral Gay–Berne model, were performed to investigate the effect of central longitudinal dipole interactions on phase behavior. A systematic analysis of the structural properties and phase behavior of both achiral and chiral systems, with dipole interactions, reveals differing effects; strong dipole interactions enhance the formation of layered structures; however, chiral interactions may prevent the formation of such phases under certain conditions. We also observed a short-ranged smectic structure within the cholesteric phases with strong dipole interactions. This constitutes possible evidence of presmectic ordering and/or the existence of chiral line liquid phases, which have previously been observed in X-ray experiments to occur between the smectic twisted grain boundary and cholesteric phases. These results provide a systematic understanding of how the phase behavior of chiral liquid-crystals changes when alterations are made to the strength of dipole interactions.
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Affiliation(s)
- Takuma Nozawa
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
| | - Paul E Brumby
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
| | - Kenji Yasuoka
- Department of Mechanical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
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11
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Sentker K, Zantop AW, Lippmann M, Hofmann T, Seeck OH, Kityk AV, Yildirim A, Schönhals A, Mazza MG, Huber P. Quantized Self-Assembly of Discotic Rings in a Liquid Crystal Confined in Nanopores. PHYSICAL REVIEW LETTERS 2018; 120:067801. [PMID: 29481274 DOI: 10.1103/physrevlett.120.067801] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/21/2017] [Indexed: 05/16/2023]
Abstract
Disklike molecules with aromatic cores spontaneously stack up in linear columns with high, one-dimensional charge carrier mobilities along the columnar axes, making them prominent model systems for functional, self-organized matter. We show by high-resolution optical birefringence and synchrotron-based x-ray diffraction that confining a thermotropic discotic liquid crystal in cylindrical nanopores induces a quantized formation of annular layers consisting of concentric circular bent columns, unknown in the bulk state. Starting from the walls this ring self-assembly propagates layer by layer towards the pore center in the supercooled domain of the bulk isotropic-columnar transition and thus allows one to switch on and off reversibly single, nanosized rings through small temperature variations. By establishing a Gibbs free energy phase diagram we trace the phase transition quantization to the discreteness of the layers' excess bend deformation energies in comparison to the thermal energy, even for this near room-temperature system. Monte Carlo simulations yielding spatially resolved nematic order parameters, density maps, and bond-orientational order parameters corroborate the universality and robustness of the confinement-induced columnar ring formation as well as its quantized nature.
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Affiliation(s)
- Kathrin Sentker
- Institut für Materialphysik und -technologie, Technische Universität Hamburg (TUHH), Eißendorferstr. 42, D-21073 Hamburg, Germany
| | - Arne W Zantop
- Max-Planck-Institut für Dynamik und Selbstorganisation, Am Faßberg 17, D-37077 Göttingen, Germany
| | - Milena Lippmann
- Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, D-22607 Hamburg, Germany
| | - Tommy Hofmann
- Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany
| | - Oliver H Seeck
- Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, D-22607 Hamburg, Germany
| | - Andriy V Kityk
- Faculty of Electrical Engineering, Czestochowa University of Technology, Al. Armii Krajowej 17, P-42-200 Czestochowa, Poland
| | - Arda Yildirim
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany
| | - Andreas Schönhals
- Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, D-12205 Berlin, Germany
| | - Marco G Mazza
- Max-Planck-Institut für Dynamik und Selbstorganisation, Am Faßberg 17, D-37077 Göttingen, Germany
| | - Patrick Huber
- Institut für Materialphysik und -technologie, Technische Universität Hamburg (TUHH), Eißendorferstr. 42, D-21073 Hamburg, Germany
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12
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Wu L, Sun H. Cholesteric ordering predicted using a coarse-grained polymeric model with helical interactions. SOFT MATTER 2018; 14:344-353. [PMID: 29211101 DOI: 10.1039/c7sm02077e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The understanding of cholesteric liquid crystals at a molecular level is challenging. Limited insights are available to bridge between molecular structures and macroscopic chiral organization. In the present study, we introduce a novel coarse-grained (CG) molecular model, which is represented by flexible chain particles with helical interactions (FCh), to study the liquid crystalline phase behavior of cholesteric molecules such as double strand DNA and α-helix polypeptides using molecular dynamics (MD) simulations. The isotropic-cholesteric phase transitions of FCh molecules were simulated for varying chain flexibilities. A wall confinement was used to break the periodicity along the cholesteric helix director in order to predict the equilibrium cholesteric pitch. The left-handed cholesteric phase was shown for FCh molecules with right-handed chiral interactions, and a spatially inhomogeneous distribution of the nematic order parameter profile was observed in cholesteric phases. It was found that the chain flexibility plays an important role in determining the macroscopic cholesteric pitch and the structure of the cholesteric liquid crystal phase. The simulations provide insight into the relationship between microscopic molecular characteristics and the macroscopic phase behavior.
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Affiliation(s)
- Liang Wu
- School of Chemistry and Chemical Engineering, Key Laboratory of Scientific and Engineering Computing of Ministry of Education, Shanghai Jiao Tong University, 200240, Shanghai, China.
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13
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Busch M, Kityk AV, Piecek W, Hofmann T, Wallacher D, Całus S, Kula P, Steinhart M, Eich M, Huber P. A ferroelectric liquid crystal confined in cylindrical nanopores: reversible smectic layer buckling, enhanced light rotation and extremely fast electro-optically active Goldstone excitations. NANOSCALE 2017; 9:19086-19099. [PMID: 29199756 DOI: 10.1039/c7nr07273b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The orientational and translational order of a thermotropic ferroelectric liquid crystal (2MBOCBC) imbibed in self-organized, parallel, cylindrical pores with radii of 10, 15, or 20 nm in anodic aluminium oxide monoliths (AAO) are explored by high-resolution linear and circular optical birefringence as well as neutron diffraction texture analysis. The results are compared to experiments on the bulk system. The native oxidic pore walls do not provide a stable smectogen wall anchoring. By contrast, a polymeric wall grafting enforcing planar molecular anchoring results in a thermal-history independent formation of smectic C* helices and a reversible chevron-like layer buckling. An enhancement of the optical rotatory power by up to one order of magnitude of the confined compared to the bulk liquid crystal is traced to the pretransitional formation of helical structures at the smectic-A*-to-smectic-C* transformation. A linear electro-optical birefringence effect evidences collective fluctuations in the molecular tilt vector direction along the confined helical superstructures, i.e. the Goldstone phason excitations typical of the para-to-ferroelectric transition. Their relaxation frequencies increase with the square of the inverse pore radii as characteristic of plane-wave excitations and are two orders of magnitude larger than in the bulk, evidencing an exceptionally fast electro-optical functionality of the liquid-crystalline-AAO nanohybrids.
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Affiliation(s)
- Mark Busch
- Institute of Materials Physics and Technology, Hamburg University of Technology, 21073 Hamburg, Germany.
| | - Andriy V Kityk
- Institute of Materials Physics and Technology, Hamburg University of Technology, 21073 Hamburg, Germany. and Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland.
| | - Wiktor Piecek
- Military University of Technology, 00-908 Warsaw, Poland
| | - Tommy Hofmann
- Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Dirk Wallacher
- Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Sylwia Całus
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland.
| | | | - Martin Steinhart
- Institute for the Chemistry of New Materials, University Osnabrück, 49067 Osnabrück, Germany
| | - Manfred Eich
- Institute of Optical and Electronic Materials, Hamburg University of Technology, 21073 Hamburg, Germany and Institute of Materials Research, Helmholtz-Zentrum Geesthacht, 21502 Geesthacht, Germany
| | - Patrick Huber
- Institute of Materials Physics and Technology, Hamburg University of Technology, 21073 Hamburg, Germany.
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