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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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Brinker M, Huber P. Wafer-Scale Electroactive Nanoporous Silicon: Large and Fully Reversible Electrochemo-Mechanical Actuation in Aqueous Electrolytes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2105923. [PMID: 34677879 DOI: 10.1002/adma.202105923] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/08/2021] [Indexed: 06/13/2023]
Abstract
Nanoporosity in silicon results in interface-dominated mechanics, fluidics, and photonics that are often superior to the ones of the bulk material. However, their active control, for example, by electronic stimuli, is challenging due to the absence of intrinsic piezoelectricity in the base material. Here, for large-scale nanoporous silicon cantilevers wetted by aqueous electrolytes, electrosorption-induced mechanical stress generation of up to 600 kPa that is reversible and adjustable at will by potential variations of ≈1 V is shown. Laser cantilever bending experiments in combination with in operando voltammetry and step coulombmetry allow this large electro-actuation to be traced to the concerted action of 100 billions of parallel nanopores per square centimeter cross-section and determination of the capacitive charge-stress coupling parameter upon ion adsorption and desorption as well as the intimately related stress actuation dynamics for perchloric and isotonic saline solutions. A comparison with planar silicon surfaces reveals mechanistic insights on the observed electrocapillarity (Hellmann-Feynman interactions) with respect to the importance of oxide formation and wall roughness on the single-nanopore scale. The observation of robust electrochemo-mechanical actuation in a mainstream semiconductor with wafer-scale, self-organized nanoporosity opens up novel opportunities for on-chip integrated stress generation and actuorics at exceptionally low operation voltages.
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Affiliation(s)
- Manuel Brinker
- Institute for Materials and X-Ray Physics, Hamburg University of Technology, 21073, Hamburg, Germany
- Center for X-Ray and Nano Science CXNS, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
- Center for Hybrid Nanostructures CHyN, University of Hamburg, 22607, Hamburg, Germany
| | - Patrick Huber
- Institute for Materials and X-Ray Physics, Hamburg University of Technology, 21073, Hamburg, Germany
- Center for X-Ray and Nano Science CXNS, Deutsches Elektronen-Synchrotron DESY, 22607, Hamburg, Germany
- Center for Hybrid Nanostructures CHyN, University of Hamburg, 22607, Hamburg, Germany
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3
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Abstract
Smart soft materials are envisioned to be the building blocks of the next generation of advanced devices and digitally augmented technologies. In this context, liquid crystals (LCs) owing to their responsive and adaptive attributes could serve as promising smart soft materials. LCs played a critical role in revolutionizing the information display industry in the 20th century. However, in the turn of the 21st century, numerous beyond-display applications of LCs have been demonstrated, which elegantly exploit their controllable stimuli-responsive and adaptive characteristics. For these applications, new LC materials have been rationally designed and developed. In this Review, we present the recent developments in light driven chiral LCs, i.e., cholesteric and blue phases, LC based smart windows that control the entrance of heat and light from outdoor to the interior of buildings and built environments depending on the weather conditions, LC elastomers for bioinspired, biological, and actuator applications, LC based biosensors for detection of proteins, nucleic acids, and viruses, LC based porous membranes for the separation of ions, molecules, and microbes, living LCs, and LCs under macro- and nanoscopic confinement. The Review concludes with a summary and perspectives on the challenges and opportunities for LCs as smart soft materials. This Review is anticipated to stimulate eclectic ideas toward the implementation of the nature's delicate phase of matter in future generations of smart and augmented devices and beyond.
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Affiliation(s)
- Hari Krishna Bisoyi
- Advanced Materials and Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, United States
| | - Quan Li
- Advanced Materials and Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, United States.,Institute of Advanced Materials, School of Chemistry and Chemical Engineering, and Jiangsu Hi-Tech Key Laboratory for Biomedical Research, Southeast University, Nanjing 211189, China
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4
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Kityk AV, Nowak M, Reben M, Pawlik P, Lelonek M, Andrushchak A, Shchur Y, Andrushchak N, Huber P. Dynamic Kerr and Pockels electro-optics of liquid crystals in nanopores for active photonic metamaterials. NANOSCALE 2021; 13:18714-18725. [PMID: 34739018 PMCID: PMC8601124 DOI: 10.1039/d1nr04282c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 09/13/2021] [Indexed: 06/13/2023]
Abstract
Photonic metamaterials with properties unattainable in base materials are already beginning to revolutionize optical component design. However, their exceptional characteristics are often static, as artificially engineered into the material during the fabrication process. This limits their application for in-operando adjustable optical devices and active optics in general. Here, for a hybrid material consisting of a liquid crystal-infused nanoporous solid, we demonstrate active and dynamic control of its meta-optics by applying alternating electric fields parallel to the long axes of its cylindrical pores. First-harmonic Pockels and second-harmonic Kerr birefringence responses, strongly depending on the excitation frequency and temperature, are observed in a frequency range from 50 Hz to 50 kHz. This peculiar behavior is quantitatively traced by a Landau-De Gennes free energy analysis to an order-disorder orientational transition of the rod-like mesogens and intimately related changes in the molecular mobilities and polar anchoring at the solid walls on the single-pore, meta-atomic scale. Thus, our study provides evidence that liquid crystal-infused nanopores exhibit integrated multi-physical couplings and reversible phase changes that make them particularly promising for the design of photonic metamaterials with thermo-electrically tunable birefringence in the emerging field of space-time metamaterials aiming at full spatio-temporal control of light.
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Affiliation(s)
- Andriy V Kityk
- Faculty of Electrical Engineering, Czestochowa University of Technology, Al. Armii Krajowej 17, 42-200 Czestochowa, Poland.
| | - Marcjan Nowak
- Faculty of Electrical Engineering, Czestochowa University of Technology, Al. Armii Krajowej 17, 42-200 Czestochowa, Poland.
| | - Manuela Reben
- Faculty of Materials Science and Ceramics, AGH-University of Science and Technology, al. Mickiewicza 30, 30-059 Cracow, Poland
| | - Piotr Pawlik
- Faculty of Production Engineering and Materials Science, Czestochowa University of Technology, Al. Armii Krajowej 19, 42-200 Czestochowa, Poland
| | - Monika Lelonek
- SmartMembranes GmbH, Heinrich-Damerow-Str. 4, 06120 Halle(Saale), Germany
| | - Anatoliy Andrushchak
- Department of Applied Physics and Nanomaterials Science, Lviv Polytechnic National University, 12 Bandery Str., Lviv 79013, Ukraine
| | - Yaroslav Shchur
- Institute for Condensed Matter Physics, 1 Svientsitskii str., 79011 Lviv, Ukraine
| | - Nazariy Andrushchak
- Department of Computer-Aided Design Systems, Lviv Polytechnic National University, 12 Bandery Str., Lviv 79013, Ukraine
- Private Enterprise SoftPartners, 97 Konovalca str., 79057 Lviv, Ukraine
| | - Patrick Huber
- Hamburg University of Technology, Institute for Materials and X-Ray Physics, 21073 Hamburg, Germany.
- Deutsches Elektronen-Synchrotron DESY, Centre for X-Ray and Nano Science CXNS, 22607 Hamburg, Germany
- Hamburg University, Centre for Hybrid Nanostructures CHyN, 22607 Hamburg, Germany
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5
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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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6
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Laser-excited elastic guided waves reveal the complex mechanics of nanoporous silicon. Nat Commun 2021; 12:3597. [PMID: 34127659 PMCID: PMC8203614 DOI: 10.1038/s41467-021-23398-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 04/21/2021] [Indexed: 11/18/2022] Open
Abstract
Nanoporosity in silicon leads to completely new functionalities of this mainstream semiconductor. A difficult to assess mechanics has however significantly limited its application in fields ranging from nanofluidics and biosensorics to drug delivery, energy storage and photonics. Here, we present a study on laser-excited elastic guided waves detected contactless and non-destructively in dry and liquid-infused single-crystalline porous silicon. These experiments reveal that the self-organised formation of 100 billions of parallel nanopores per square centimetre cross section results in a nearly isotropic elasticity perpendicular to the pore axes and an 80% effective stiffness reduction, altogether leading to significant deviations from the cubic anisotropy observed in bulk silicon. Our thorough assessment of the wafer-scale mechanics of nanoporous silicon provides the base for predictive applications in robust on-chip devices and evidences that recent breakthroughs in laser ultrasonics open up entirely new frontiers for in-situ, non-destructive mechanical characterisation of dry and liquid-functionalised porous materials. Assessing mechanics of nanoporous silicon is challenging, but important for new applications. Here, the authors use non-destructive laser-excited elastic guided waves detected contactless, to study dry and liquid-infused single-crystalline porous silicon, revealing its complex mechanics and significant deviations from bulk silicon.
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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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Yildirim A, Sentker K, Smales GJ, Pauw BR, Huber P, Schönhals A. Collective orientational order and phase behavior of a discotic liquid crystal under nanoscale confinement. NANOSCALE ADVANCES 2019; 1:1104-1116. [PMID: 36133215 PMCID: PMC9473266 DOI: 10.1039/c8na00308d] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 12/03/2018] [Indexed: 05/30/2023]
Abstract
The phase behavior and molecular ordering of hexakishexyloxy triphenylene (HAT6) DLCs under cylindrical nanoconfinement are studied utilizing differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), where cylindrical nanoconfinement is established through embedding HAT6 into the nanopores of anodic aluminum oxide (AAO) membranes, and a silica membrane with pore diameters ranging from 161 nm down to 12 nm. Both unmodified and modified pore walls were considered. In the latter case the pore walls of AAO membranes were chemically treated with n-octadecylphosphonic acid (ODPA) resulting in the formation of a 2.2 nm thick layer of grafted alkyl chains. Phase transition enthalpies decrease with decreasing pore size, indicating that a large proportion of the HAT6 molecules within the pores has a disordered structure, which increases with decreasing pore size for both pore walls. In the case of the ODPA-modification, the amount of ordered HAT6 is increased compared to the unmodified case. The pore size dependencies of the phase transition temperatures were approximated using the Gibbs-Thomson equation, where the estimated surface tension is dependent on the molecular ordering of HAT6 molecules within the pores and upon their surface. DS was employed to investigate the molecular ordering of HAT6 within the nanopores. These investigations revealed that with a pore size of around 38 nm, for the samples with the unmodified pore walls, the molecular ordering changes from planar axial to homeotropic radial. However, the planar axial configuration, which is suitable for electronic applications, can be successfully preserved through ODPA-modification for most of the pore sizes.
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Affiliation(s)
- Arda Yildirim
- Bundesanstalt für Materialforschung und-prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany +49 30/8104-3384
| | - Kathrin Sentker
- Institut für Materialphysik und-technologie, Technische Universität Hamburg Eißendorfer Str. 42 21073 Hamburg Germany
| | - Glen Jacob Smales
- Bundesanstalt für Materialforschung und-prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany +49 30/8104-3384
| | - Brian Richard Pauw
- Bundesanstalt für Materialforschung und-prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany +49 30/8104-3384
| | - Patrick Huber
- Institut für Materialphysik und-technologie, Technische Universität Hamburg Eißendorfer Str. 42 21073 Hamburg Germany
| | - Andreas Schönhals
- Bundesanstalt für Materialforschung und-prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany +49 30/8104-3384
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9
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Park W, Feringán B, Yang M, Ryu SH, Ahn H, Shin TJ, Sierra T, Giménez R, Yoon DK. Manipulation of Supramolecular Columnar Structures of H-Bonded Donor-Acceptor Units through Geometrical Nanoconfinement. Chemphyschem 2019; 20:890-897. [PMID: 30730103 DOI: 10.1002/cphc.201801042] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 12/23/2018] [Indexed: 11/12/2022]
Abstract
Ambipolar organic semiconductors are considered promising for organic electronics because of their interesting electric properties. Many hurdles remain yet to be overcome before they can be used for practical applications, especially because their orientation is hard to control. We demonstrate a method to control the orientation of columnar structures based on a hydrogen (H)-bonded donor-acceptor complex between a star-shaped tris(triazolyl)triazine and triphenylene-containing benzoic acid, using physicochemical nanoconfinement. The molecular configuration and supramolecular columnar assemblies in a one-dimensional porous anodic aluminium oxide (AAO) film were dramatically modulated by controlling the pore-size and by chemical modification of the inner surface of the porous AAO film. In situ experiments using grazing-incidence X-ray diffraction (GIXRD) were carried out to investigate the structural evolution produced at the nanometer scale by varying physicochemical conditions. The resulting highly ordered nanostructures may open a new pathway to effectively control the alignment of liquid crystal ambipolar semiconductors.
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Affiliation(s)
- Wongi Park
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Beatriz Feringán
- Departamento de Química Orgánica Instituto de Ciencia de Materiales de Aragón (ICMA) Facultad de Ciencias, Universidad de Zaragoza-CSIC, Zaragoza, 50009, Spain
| | - Minyong Yang
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Seong Ho Ryu
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Hyungju Ahn
- Pohang Accelerator Laboratory, POSTECH, Pohang, 37673, Republic of Korea
| | - Tae Joo Shin
- UNIST Central Research Facilities and, School of Natural Science UNIST, Ulsan, 44919, Republic of Korea
| | - Teresa Sierra
- Departamento de Química Orgánica Instituto de Ciencia de Materiales de Aragón (ICMA) Facultad de Ciencias, Universidad de Zaragoza-CSIC, Zaragoza, 50009, Spain
| | - Raquel Giménez
- Departamento de Química Orgánica Instituto de Ciencia de Materiales de Aragón (ICMA) Facultad de Ciencias, Universidad de Zaragoza-CSIC, Zaragoza, 50009, Spain
| | - Dong Ki Yoon
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.,Department of Chemistry and KINC, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
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10
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Cetinkaya MC, Ustunel S, Ozbek H, Yildiz S, Thoen J. Convincing evidence for the Halperin-Lubensky-Ma effect at the N-SmA transition in alkyloxycyanobiphenyl binary mixtures via a high-resolution birefringence study. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:129. [PMID: 30353409 DOI: 10.1140/epje/i2018-11738-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 10/01/2018] [Indexed: 06/08/2023]
Abstract
We present new high-resolution experimental data for the temperature behavior of optical birefringence for a series of mixture of the liquid crystals octyloxycyanobiphenyl (8OCB) and nonyloxycyanobiphenyl (9OCB) by using a rotating analyzer technique. The birefringence data have been used to probe the temperature dependence of the nematic order parameter [Formula: see text]. We have then arrived at values for possible entropy discontinuities at the nematic-smectic A transition temperature [Formula: see text] from the detailed inspection of [Formula: see text] data in the immediate vicinity of [Formula: see text]. The 9OCB mole fraction dependence of the obtained reduced entropy discontinuities has been shown to be well fitted with a crossover function which is itself consistent with the mean-field free energy expression with a non-zero cubic term arising from the Halperin-Lubensky-Ma (HLM) coupling. The obtained results are in good accordance with existing results from adiabatic scanning calorimetry (ASC). Our birefringence results and determined entropy discontinuities (consistent with calorimetry results) are in striking contrast with the recent birefringence results of Barman et al. (Phase Transit. 91, 58 (2018) published online 16 Aug. 2017) claiming second-order nematic-to-smectic A transitions for all mixtures. In this paper we present a possible explanation for this discrepancy. We have also extracted the effective critical exponent values [Formula: see text] characterizing the critical fluctuations near the N-SmA transition for all compositions by using the fact that the temperature derivative of the order parameter [Formula: see text] near [Formula: see text] exhibits the same power-law divergence as the specific heat capacity. Measurable latent heat values were extracted from optical birefringence data for mole fractions of 9OCB where the [Formula: see text] values are as low as 0.2, which is substantially lower than the tricritical value [Formula: see text]. This is qualitatively different from what has been observed so far in other liquid-crystal systems. Together with ASC data, these pecuilarities of the 8OCB+9OCB system render further convincing evidence for the presence of the HLM coupling effect at the N-SmA transition phase transition line.
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Affiliation(s)
- M C Cetinkaya
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - S Ustunel
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - H Ozbek
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - S Yildiz
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey.
| | - J Thoen
- Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, 3001, Leuven, Belgium
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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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Yildirim A, Szymoniak P, Sentker K, Butschies M, Bühlmeyer A, Huber P, Laschat S, Schönhals A. Dynamics and ionic conductivity of ionic liquid crystals forming a hexagonal columnar mesophase. Phys Chem Chem Phys 2018; 20:5626-5635. [DOI: 10.1039/c7cp08186c] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different lengths of alkyl chains was investigated using a combination of broadband dielectric (BDS) and specific heat spectroscopy (SHS).
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Affiliation(s)
- Arda Yildirim
- Bundesanstalt für Materialforschung und -prüfung (BAM)
- Unter den Eichen 87
- 12205 Berlin
- Germany
| | - Paulina Szymoniak
- Bundesanstalt für Materialforschung und -prüfung (BAM)
- Unter den Eichen 87
- 12205 Berlin
- Germany
| | - Kathrin Sentker
- Institut für Materialphysik und -Technologie
- Technische Universität Hamburg
- Eißendorfer Str. 42
- 21073 Hamburg
- Germany
| | - Martin Butschies
- Institut für Organische Chemie
- Universität Stuttgart
- Pfaffenwaldring 55
- 70569 Stuttgart
- Germany
| | - Andrea Bühlmeyer
- Institut für Organische Chemie
- Universität Stuttgart
- Pfaffenwaldring 55
- 70569 Stuttgart
- Germany
| | - Patrick Huber
- Institut für Materialphysik und -Technologie
- Technische Universität Hamburg
- Eißendorfer Str. 42
- 21073 Hamburg
- Germany
| | - Sabine Laschat
- Institut für Organische Chemie
- Universität Stuttgart
- Pfaffenwaldring 55
- 70569 Stuttgart
- Germany
| | - Andreas Schönhals
- Bundesanstalt für Materialforschung und -prüfung (BAM)
- Unter den Eichen 87
- 12205 Berlin
- Germany
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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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14
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Zhang RB, Ungar G, Zeng X, Shen Z. Diverse configurations of columnar liquid crystals in cylindrical nano- and micropores. SOFT MATTER 2017; 13:4122-4131. [PMID: 28548148 DOI: 10.1039/c7sm00620a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Using 2D X-ray diffraction and AFM we studied the configuration, in cylindrical confinement, of hexagonal columnar phases that anchor homeotropically, i.e. with the columns normal to the pore wall. A wide range of pore diameters, from 20 nm to 100 μm, were explored by employing anodic alumina membranes and glass capillaries. The compounds used were a small discotic, hexakis(hexyloxy)triphenylene (HAT6), a large discotic hexa-peri-hexabenzocoronene (HBC), and a T-shaped bolaamphiphile, forming a honeycomb-type columnar phase. It was found that in pores up to tens of μm in diameter the columns adopt the "logpile" configuration with parallel columns crossing the pore perpendicular to its axis. Starting with 20 nm pores, with increasing pore diameter up to 5 different configurations are observed, the sequence being the same for all three compounds in spite of their structural diversity. One of the {100} planes of the hexagonal logpile starts from being parallel to the pore axis, then rotates by 90° as the pore size increases, and eventually becomes tilted to the pore axis by (8.5 ± 1)° as the pore widens further. Finally, in glass capillaries of tens of μm and beyond, the columns become axially oriented, parallel to the capillary axis. This latter finding was particularly unexpected as common sense would suggest axial columns to be favoured by planar anchoring, where in fact, it was shown to be hard to achieve. The present findings should help in the design of low-dimensional semiconductor or ionic conductor devices based on oriented columnar phases.
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Affiliation(s)
- Rui-Bin Zhang
- Department of Physics, Zhejiang Sci-Tech University, Xiasha College Park, Hangzhou 310018, China.
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15
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Yıldız S, Çetinkaya MC, Üstünel Ş, Özbek H, Thoen J. Test of Halperin-Lubensky-Ma crossover function at the N-Sm-A transition in liquid crystal binary mixtures via high-resolution birefringence measurements. Phys Rev E 2016; 93:062706. [PMID: 27415333 DOI: 10.1103/physreve.93.062706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Indexed: 11/07/2022]
Abstract
We report optical birefringence data for a series of mixtures of the liquid crystals octylcyanobiphenyl (8CB) and decylcyanobiphenyl (10CB). Nematic order parameter S data in the nematic and smectic A phases have been derived from phase angle changes obtained in temperature scans with a rotating analyzer method. These S values have been used to arrive at values for possible entropy discontinuities at the smectic A to nematic phase transition temperature T_{NA}. The 10CB mole fraction dependence of the obtained entropy discontinuities could be well fitted with a crossover function consistent with the mean-field free-energy expression with a nonzero cubic term arising from the coupling between the smectic-A order parameter and the orientational order parameter director fluctuations in the Halperin-Lubensky-Ma theory. The obtained results are in good agreement with existing results from adiabatic scanning calorimetry. By exploiting the fact that the temperature derivative of the order parameter S(T) near T_{NA} exhibits the same power law divergence as the specific heat capacity, we have extracted the effective critical exponent α values for the compositions under study. The critical exponent α has been observed to reach the tricritical value α_{TCP}=0.5 for the 10CB mole fraction of x=0.330.
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Affiliation(s)
- Sevtap Yıldız
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - Mehmet Can Çetinkaya
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - Şenay Üstünel
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - Haluk Özbek
- Department of Physics, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - Jan Thoen
- Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, 3001 Leuven, Belgium
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16
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Wöhrle T, Wurzbach I, Kirres J, Kostidou A, Kapernaum N, Litterscheidt J, Haenle JC, Staffeld P, Baro A, Giesselmann F, Laschat S. Discotic Liquid Crystals. Chem Rev 2015; 116:1139-241. [PMID: 26483267 DOI: 10.1021/acs.chemrev.5b00190] [Citation(s) in RCA: 418] [Impact Index Per Article: 46.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tobias Wöhrle
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Iris Wurzbach
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Jochen Kirres
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Antonia Kostidou
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Nadia Kapernaum
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Juri Litterscheidt
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Johannes Christian Haenle
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Peter Staffeld
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Angelika Baro
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Frank Giesselmann
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
| | - Sabine Laschat
- Institut für Organische Chemie, and ‡Institut für Physikalische Chemie, Universität Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany
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17
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Temperature-dependent electro-optical and elastic properties of carbon nanotube doped polar smectogen octylcyanobiphenyl. J Mol Liq 2015. [DOI: 10.1016/j.molliq.2015.06.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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18
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Całus S, Kityk AV, Borowik L, Lefort R, Morineau D, Krause C, Schönhals A, Busch M, Huber P. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012503. [PMID: 26274191 DOI: 10.1103/physreve.92.012503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Indexed: 05/16/2023]
Abstract
We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites.
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Affiliation(s)
- Sylwia Całus
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland
| | - Andriy V Kityk
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland
| | - Lech Borowik
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland
| | - Ronan Lefort
- Institut de Physique de Rennes, UMR 6251, Université de Rennes 1, 35042 Rennes, France
| | - Denis Morineau
- Institut de Physique de Rennes, UMR 6251, Université de Rennes 1, 35042 Rennes, France
| | - Christina Krause
- BAM Federal Institute for Materials Research and Testing, D-12203 Berlin, Germany
| | - Andreas Schönhals
- BAM Federal Institute for Materials Research and Testing, D-12203 Berlin, Germany
| | - Mark Busch
- Institute of Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg, Germany
| | - Patrick Huber
- Institute of Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg, Germany
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19
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Całus S, Kityk AV, Eich M, Huber P. Inhomogeneous relaxation dynamics and phase behaviour of a liquid crystal confined in a nanoporous solid. SOFT MATTER 2015; 11:3176-3187. [PMID: 25759093 DOI: 10.1039/c5sm00108k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report filling-fraction dependent dielectric spectroscopy measurements on the relaxation dynamics of the rod-like nematogen 7CB condensed in 13 nm silica nanochannels. In the film-condensed regime, a slow interface relaxation dominates the dielectric spectra, whereas from the capillary-condensed state up to complete filling an additional, fast relaxation in the core of the channels is found. The temperature-dependence of the static capacitance, representative of the averaged, collective molecular orientational ordering, indicates a continuous, paranematic-to-nematic (P-N) transition, in contrast to the discontinuous bulk behaviour. It is well described by a Landau-de-Gennes free energy model for a phase transition in cylindrical confinement. The large tensile pressure of 10 MPa in the capillary-condensed state, resulting from the Young-Laplace pressure at highly curved liquid menisci, quantitatively accounts for a downward-shift of the P-N transition and an increased molecular mobility in comparison to the unstretched liquid state of the complete filling. The strengths of the slow and fast relaxations provide local information on the orientational order: the thermotropic behaviour in the core region is bulk-like, i.e. it is characterized by an abrupt onset of the nematic order at the P-N transition. By contrast, the interface ordering exhibits a continuous evolution at the P-N transition. Thus, the phase behaviour of the entirely filled liquid crystal-silica nanocomposite can be quantitatively described by a linear superposition of these distinct nematic order contributions.
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Affiliation(s)
- Sylwia Całus
- Faculty of Electrical Engineering, Czestochowa University of Technology, Al. Armii Krajowej 17, 42-200 Czestochowa, Poland.
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20
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Huber P. Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:103102. [PMID: 25679044 DOI: 10.1088/0953-8984/27/10/103102] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications. A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.
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Affiliation(s)
- Patrick Huber
- Hamburg University of Technology (TUHH), Institute of Materials Physics and Technology, Eißendorfer Str. 42, D-21073 Hamburg-Harburg (Germany
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21
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Zhang R, Zeng X, Kim B, Bushby RJ, Shin K, Baker PJ, Percec V, Leowanawat P, Ungar G. Columnar liquid crystals in cylindrical nanoconfinement. ACS NANO 2015; 9:1759-1766. [PMID: 25626118 DOI: 10.1021/nn506605p] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Axial orientation of discotic columnar liquid crystals in nanopores of inorganic templates, with the columns parallel to the axis of the nanochannels, is considered desirable for applications such as production of molecular wires. Here, we evaluate experimentally the role of the rigidity of the LC columns in achieving such orientation in nanopores where the planar anchoring (i.e., columns parallel to wall surface) is enforced. We studied the columnar phase of several discotic compounds with increasing column rigidity in the following order: dendronized carbazole, hexakis(hexyloxy)triphenylene (HAT6), a 1:1 HAT6-trinitrofluorenone (TNF) complex, and a helicene derivative. Using 2-D X-ray diffraction, AFM, grazing incidence diffraction, and polarized microscopy, we observed that the orientation of the columns changes from circular concentric to axial with increasing column rigidity. Additionally, when the rigidity is borderline, increasing pore diameter can change the configuration from axial back to circular. We derive expressions for distortion free energy that suggest that the orientation is determined by the competition between, on the one hand, the distortion energy of the 2-d lattice and the mismatch of its crystallographic facets with the curved pore wall in the axial orientation and, on the other hand, the bend energy of the columns in the circular configuration. Furthermore, the highly detailed AFM images of the core of the disclinations of strength +1 and +1/2 in the center of the pore reveal that the columns spiral down to the very center of the disclination and that there is no amorphous or misaligned region at the core, as suggested previously.
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Affiliation(s)
- Ruibin Zhang
- Department of Materials Science and Engineering, University of Sheffield , Sheffield S1 3JD, U.K
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22
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Pang J, Li X, Zhou G, Sun B, Wei Y. Fabrication of mesoporous silica nanospheres with radially oriented mesochannels by microemulsion templating for adsorption and controlled release of aspirin. RSC Adv 2015. [DOI: 10.1039/c4ra12291g] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The MSN spheres with narrow size distribution and radially oriented mesoporous channels were prepared using an O/W microemulsion system, consisting of CTAB (or PVP), ethanol, cyclohexane and water as template.
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Affiliation(s)
- Jinli Pang
- Key Laboratory of Fine Chemicals in Universities of Shandong
- School of Chemistry and Pharmaceutical Engineering
- Qilu University of Technology
- Jinan 250353
- People's Republic of China
| | - Xiuyan Li
- Key Laboratory of Fine Chemicals in Universities of Shandong
- School of Chemistry and Pharmaceutical Engineering
- Qilu University of Technology
- Jinan 250353
- People's Republic of China
| | - Guowei Zhou
- Key Laboratory of Fine Chemicals in Universities of Shandong
- School of Chemistry and Pharmaceutical Engineering
- Qilu University of Technology
- Jinan 250353
- People's Republic of China
| | - Bin Sun
- Key Laboratory of Fine Chemicals in Universities of Shandong
- School of Chemistry and Pharmaceutical Engineering
- Qilu University of Technology
- Jinan 250353
- People's Republic of China
| | - Yingqin Wei
- Key Laboratory of Fine Chemicals in Universities of Shandong
- School of Chemistry and Pharmaceutical Engineering
- Qilu University of Technology
- Jinan 250353
- People's Republic of China
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23
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Ndao M, Lefort R, Cerclier CV, Busselez R, Morineau D, Frick B, Ollivier J, Kityk AV, Huber P. Molecular dynamics of pyrene based discotic liquid crystals confined in nanopores probed by incoherent quasielastic neutron scattering. RSC Adv 2014. [DOI: 10.1039/c4ra13032d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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24
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Całus S, Jabłońska B, Busch M, Rau D, Huber P, Kityk AV. Paranematic-to-nematic ordering of a binary mixture of rodlike liquid crystals confined in cylindrical nanochannels. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:062501. [PMID: 25019799 DOI: 10.1103/physreve.89.062501] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Indexed: 06/03/2023]
Abstract
We explore the optical birefringence of the nematic binary mixtures 6CB_{1-x}7CB_{x} (0 ≤ x ≤ 1) embedded into parallel-aligned nanochannels of mesoporous alumina and silica membranes for channel radii of 3.4 ≤ R ≤ 21.0 nm. The results are compared with the bulk behavior and analyzed with a Landau-de Gennes model. Depending on the channel radius the nematic ordering in the cylindrical nanochannels evolves either discontinuously (subcritical regime, nematic ordering field σ<1/2) or continuously (overcritical regime, σ>1/2), but in both cases with a characteristic paranematic precursor behavior. The strength of the ordering field, imposed by the channel walls, and the magnitude of quenched disorder varies linearly with the mole fraction x and scales inversely proportionally with R for channel radii larger than 4 nm. The critical pore radius, R_{c}, separating a continuous from a discontinuous paranematic-to-nematic evolution varies linearly with x and differs negligibly between the silica and alumina membranes. We find no hints of preferred adsorption of one species at the channels walls. By contrast, a linear variation of the nematic-to-paranematic transition point T_{PN} and of the nematic ordering field σ versus x suggests that the binary mixtures of cyanobiphenyls 6CB and 7CB keep their homogeneous bulk stoichiometry also in nanoconfinement, at least for channel diameters larger than ∼7 nm.
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Affiliation(s)
- Sylwia Całus
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland
| | - Beata Jabłońska
- Faculty of Environmental Engineering and Biotechnology, Czestochowa University of Technology, 42-200 Czestochowa, Poland
| | - Mark Busch
- Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg, Germany
| | - Daniel Rau
- FR 7.2 Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany
| | - Patrick Huber
- Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg, Germany and FR 7.2 Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany
| | - Andriy V Kityk
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland
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