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El Karout H, Shchur Y, Andrushchak A, Sahraoui B, Wielgosz R, Kityk O, Jędryka J, Slyvka Y, Kityk AV. Second harmonic generation on crystalline organic nanoclusters under extreme nanoconfinement in functionalized silica-benzil composites. Sci Rep 2023; 13:9943. [PMID: 37337016 DOI: 10.1038/s41598-023-37147-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Accepted: 06/16/2023] [Indexed: 06/21/2023] Open
Abstract
We demonstrate a series of organic-inorganic nanocomposite materials combining the mesoporous silica (PS) and benzil (BZL) nanocrystals embedded into its nanochannels (6.0-13.0 nm in diameter) by capillary crystallization. One aims to design novel, efficient nonlinear optical composite materials in which inactive amorphous host PS-matrix provides a tubular scaffold structure, whereas nonlinear optical functionality results from specific properties of the deposited guest BZL-nanocrystals. A considerable contraction of the BZL melt during its crystallization inside the silica nanochannels results in a formation of the texture consisting of (221)- and (003)-oriented BZL nanoclusters (22 nm in length), separated by voids. Specificity of the textural morphology similarly to the spatial confinement significantly influences the nonlinear optical features of composite PS:BZL materials being explored in the second harmonic generation (SHG) experiment. The light polarization anisotropy of the SHG response appears to be considerably reduced at channel diameters larger than 7 nm apparently due to the multiple scattering and depolarization of the light on randomly distributed and crystallographically oriented BZL-nanoclusters. The normalized SHG response decreases nonlinearly by more than one order of magnitude as the channel diameter decreases from 13.0 to 6.0 nm and vanishes when spatial cylindrical confinement approaches the sizes of a few molecular layers suggesting that the embedded BZL clusters indeed are not uniformly crystalline but are characterized by more complex morphology consisting of a disordered SHG-inactive amorphous shell, covering the channel wall, and SHG-active crystalline core. Understanding and controlling of the textural morphology in inorganic-organic nanocrystalline composites as well as its relationships with nonlinear optical properties can lead to the development of novel efficient nonlinear optical materials for the light energy conversion with prospective optoelectronic and photonic applications.
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Affiliation(s)
- Houda El Karout
- University of Angers, LPhiA, SFR MATRIX, 2 Bd. Lavoisier, 49045, Angers Cedex 01, France
- University of Angers, MOLTECH-Anjou-UMR CNRS 6200, SFR MATRIX, 49000, Angers, France
| | - Yaroslav Shchur
- Institute for Condensed Matter Physics, 1 Svientsitskii str., Lviv, 79011, Ukraine.
| | | | - Bouchta Sahraoui
- University of Angers, LPhiA, SFR MATRIX, 2 Bd. Lavoisier, 49045, Angers Cedex 01, France
| | - Robert Wielgosz
- Energia Oze Sp. z o.o., ul. Czȩstochowska 7, 42-274, Konopiska, Poland
| | - Olha Kityk
- Energia Oze Sp. z o.o., ul. Czȩstochowska 7, 42-274, Konopiska, Poland
| | - Jarosław Jędryka
- Faculty of Electrical Engineering, Częstochowa University of Technology, Al. Armii Krajowej 17, 42-200, Częstochowa, Poland
| | - Yurii Slyvka
- Department of Inorganic Chemistry, Ivan Franko National University of Lviv, Kyryla i Mefodiya Str. 6, Lviv, 79005, Ukraine
| | - Andriy V Kityk
- Faculty of Electrical Engineering, Częstochowa University of Technology, Al. Armii Krajowej 17, 42-200, Częstochowa, Poland.
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2
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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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3
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Jasiurkowska-Delaporte M, Juszyńska-Gałązka E, Sas W, Zieliński PM, Baranowska-Korczyc A. Soft versus hard confinement effects on the phase transitions, and intra- and inter- molecular dynamics of 6BT liquid crystal constrained in electrospun polymer fibers and in nanopores. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115817] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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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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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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Ogawa S, Nakamura J. Fractal and spinodal-decomposed turbidities of nanoporous glass: fluctuation picture in turbid and transparent Vycor. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2017; 34:449-463. [PMID: 28375339 DOI: 10.1364/josaa.34.000449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The light propagation and scattering in monolithic transparent nanoporous materials such as Vycor glasses exhibit two optical turbidities, both of which are slightly deviated from the λ-4 Rayleigh wavelength dependence in the visible region: one is a transient white turbidity τf, characterized by the convex-upward dependence on the inverse fourth power of wavelength, and the other is turbidity τsp inherent to the structural inhomogeneity, characterized by the convex-downward dependence. The former is attributed to a fractal-like percolation network of imbibed or drained pores as a consequence of transient imbibition or drainage of wetting fluid into or from the pore space. The latter is attributed to the structural inhomogeneities inherent to the original dry porous glass, which are produced by spinodal decomposition. In this paper, we develop a general scheme to estimate the transmittance spectra of Vycor through the turbidities τf and τsp in the visible region on the basis of the theory of dielectric constant fluctuations. We show the applicability and its limitation of the turbidity analysis of the photospectroscopically measured data as a method to study the correlation functions that characterize the pore space and the structural features of isotropic transparent nanoporous media, on the presupposition that there exists no light attenuation other than the scattering.
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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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Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts. Colloids Surf A Physicochem Eng Asp 2016. [DOI: 10.1016/j.colsurfa.2015.09.055] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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9
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Andrews JE, Sinha S, Chung PW, Das S. Wetting dynamics of a water nanodrop on graphene. Phys Chem Chem Phys 2016; 18:23482-93. [DOI: 10.1039/c6cp01936f] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spreading of water nanodrop on supported and unsupported graphene reveals inertia-dominated behavior.
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Affiliation(s)
| | - Shayandev Sinha
- Department of Mechanical Engineering
- University of Maryland
- College Park
- USA
| | - Peter W. Chung
- Department of Mechanical Engineering
- University of Maryland
- College Park
- USA
| | - Siddhartha Das
- Department of Mechanical Engineering
- University of Maryland
- College Park
- USA
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10
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Całus S, Borowik L, Kityk AV, Eich M, Busch M, Huber P. Thermotropic interface and core relaxation dynamics of liquid crystals in silica glass nanochannels: a dielectric spectroscopy study. Phys Chem Chem Phys 2015; 17:22115-24. [PMID: 26255586 DOI: 10.1039/c5cp03039k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report dielectric relaxation spectroscopy experiments on two rod-like liquid crystals of the cyanobiphenyl family (5CB and 6CB) confined in tubular nanochannels with 7 nm radius and 340 micrometer length in a monolithic, mesoporous silica membrane. The measurements were performed on composites for two distinct regimes of fractional filling: monolayer coverage at the pore walls and complete filling of the pores. For the layer coverage a slow surface relaxation dominates the dielectric properties. For the entirely filled channels the dielectric spectra are governed by two thermally-activated relaxation processes with considerably different relaxation rates: a slow relaxation in the interface layer next to the channel walls and a fast relaxation in the core region of the channel filling. The strengths and characteristic frequencies of both relaxation processes have been extracted and analysed as a function of temperature. Whereas the temperature dependence of the static capacitance reflects the effective (average) molecular ordering over the pore volume and is well described within a Landau-de Gennes theory, the extracted relaxation strengths of the slow and fast relaxation processes provide an access to distinct local molecular ordering mechanisms. The order parameter in the core region exhibits a bulk-like behaviour with a strong increase in the nematic ordering just below the paranematic-to-nematic transition temperature TPN and subsequent saturation during cooling. By contrast, the surface ordering evolves continuously with a kink near TPN. A comparison of the thermotropic behaviour of the monolayer with the complete filling reveals that the molecular order in the core region of the pore filling affects the order of the peripheral molecular layers at the wall.
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Affiliation(s)
- Sylwia Całus
- Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland.
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11
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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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12
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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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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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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: 130] [Impact Index Per Article: 14.4] [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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15
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Carlton R, Zayas-Gonzalez YM, Manna U, Lynn DM, Abbott NL. Surfactant-induced ordering and wetting transitions of droplets of thermotropic liquid crystals "caged" inside partially filled polymeric capsules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:14944-53. [PMID: 24911044 PMCID: PMC4270404 DOI: 10.1021/la501596b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 06/08/2014] [Indexed: 05/31/2023]
Abstract
We report a study of the wetting and ordering of thermotropic liquid crystal (LC) droplets that are trapped (or "caged") within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40% of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of "free" LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurational transitions when LC droplets were caged within polymeric capsules. Specifically, upon addition of SDS to the aqueous phase, we observed the contact angles (θ) of caged LC on the interior surface of the capsule to decrease, resulting in a progression of complex droplet shapes, including lenses (θ ≈ 130 ± 10°), hemispheres (θ ≈ 89 ± 5°), and concave hemispheres (θ < 85°). The wetting transitions induced by SDS also resulted in changes in the internal ordering of the LC to yield states topologically equivalent to axial and radial configurations. Although topologically equivalent to free droplets, the contributions that surface anchoring, LC elasticity, and topological defects make to the free energy of caged LC droplets differ from those of free droplets. Overall, these results and others reported herein lead us to conclude that caged LC droplets offer a platform for new designs of LC-droplet-based responsive soft matter that cannot be realized in dispersions of free droplets.
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Affiliation(s)
- Rebecca
J. Carlton
- Department of Chemical and
Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Yashira M. Zayas-Gonzalez
- Department of Chemical and
Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Uttam Manna
- Department of Chemical and
Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - David M. Lynn
- Department of Chemical and
Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
| | - Nicholas L. Abbott
- Department of Chemical and
Biological Engineering, University of Wisconsin—Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, United States
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Kityk AV, Busch M, Rau D, Calus S, Cerclier CV, Lefort R, Morineau D, Grelet E, Krause C, Schönhals A, Frick B, Huber P. Thermotropic orientational order of discotic liquid crystals in nanochannels: an optical polarimetry study and a Landau-de Gennes analysis. SOFT MATTER 2014; 10:4522-4534. [PMID: 24832498 DOI: 10.1039/c4sm00211c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Optical polarimetry measurements of the orientational order of a discotic liquid crystal based on a pyrene derivative confined in parallelly aligned nanochannels of monolithic, mesoporous alumina, silica, and silicon as a function of temperature, channel radius (3-22 nm) and surface chemistry reveal a competition of radial and axial columnar orders. The evolution of the orientational order parameter of the confined systems is continuous, in contrast to the discontinuous transition in the bulk. For channel radii larger than 10 nm we suggest several, alternative defect structures, which are compatible both with the optical experiments on the collective molecular orientation presented here and with a translational, radial columnar order reported in previous diffraction studies. For smaller channel radii our observations can semi-quantitatively be described by a Landau-de Gennes model with a nematic shell of radially ordered columns (affected by elastic splay deformations) that coexists with an orientationally disordered, isotropic core. For these structures, the cylindrical phase boundaries are predicted to move from the channel walls to the channel centres upon cooling, and vice-versa upon heating, in accord with the pronounced cooling/heating hystereses observed and the scaling behavior of the transition temperatures with the channel diameter. The absence of experimental hints of a paranematic state is consistent with a biquadratic coupling of the splay deformations to the order parameter.
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Affiliation(s)
- Andriy V Kityk
- Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg, Germany.
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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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Gor GY, Paris O, Prass J, Russo PA, Ribeiro Carrott MML, Neimark AV. Adsorption of n-pentane on mesoporous silica and adsorbent deformation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:8601-8608. [PMID: 23758155 DOI: 10.1021/la401513n] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Development of quantitative theory of adsorption-induced deformation is important, e.g., for enhanced coalbed methane recovery by CO2 injection. It is also promising for the interpretation of experimental measurements of elastic properties of porous solids. We study deformation of mesoporous silica by n-pentane adsorption. The shape of experimental strain isotherms for this system differs from the shape predicted by thermodynamic theory of adsorption-induced deformation. We show that this difference can be attributed to the difference of disjoining pressure isotherm, responsible for the solid-fluid interactions. We suggest the disjoining pressure isotherm suitable for n-pentane adsorption on silica and derive the parameters for this isotherm from experimental data of n-pentane adsorption on nonporous silica. We use this isotherm in the formalism of macroscopic theory of adsorption-induced deformation of mesoporous materials, thus extending this theory for the case of weak solid-fluid interactions. We employ the extended theory to calculate solvation pressure and strain isotherms for SBA-15 and MCM-41 silica and compare it with experimental data obtained from small-angle X-ray scattering. Theoretical predictions for MCM-41 are in good agreement with the experiment, but for SBA-15 they are only qualitative. This deviation suggests that the elastic modulus of SBA-15 may change during pore filling.
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Affiliation(s)
- Gennady Yu Gor
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, USA.
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