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Dolganov PV, Shuravin NS, Dolganov VK, Kats EI, Stannarius R, Harth K, Trittel T, Park CS, Maclennan JE. Transient hexagonal structures in sheared emulsions of isotropic inclusions on smectic bubbles in microgravity conditions. Sci Rep 2021; 11:19144. [PMID: 34580344 PMCID: PMC8476617 DOI: 10.1038/s41598-021-98166-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 08/19/2021] [Indexed: 11/08/2022] Open
Abstract
We describe the collective behavior of isotropic droplets dispersed over a spherical smectic bubble, observed under microgravity conditions on the International Space Station (ISS). We find that droplets can form two-dimensional hexagonal structures changing with time. Our analysis indicates the possibility of spatial and temporal periodicity of such structures of droplets. Quantitative analysis of the hexagonal structure including the first three coordination circles was performed. A peculiar periodic-in-time ordering of the droplets, related to one-dimensional motion of droplets with non-uniform velocity, was found.
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Affiliation(s)
- P V Dolganov
- Institute of Solid State Physics, Russian Academy of Sciences (ISSP RAS), 142432, Chernogolovka, Moscow Region, Russia
| | - N S Shuravin
- Institute of Solid State Physics, Russian Academy of Sciences (ISSP RAS), 142432, Chernogolovka, Moscow Region, Russia
| | - V K Dolganov
- Institute of Solid State Physics, Russian Academy of Sciences (ISSP RAS), 142432, Chernogolovka, Moscow Region, Russia.
| | - E I Kats
- L.D. Landau Institute for Theoretical Physics, Russian Academy of Sciences, 142432, Chernogolovka, Moscow Region, Russia
| | - R Stannarius
- Institute of Physics, Otto von Guericke University, 39106, Magdeburg, Germany
| | - K Harth
- Institute of Physics, Otto von Guericke University, 39106, Magdeburg, Germany
| | - T Trittel
- Institute of Physics, Otto von Guericke University, 39106, Magdeburg, Germany
| | - C S Park
- Department of Physics, University of Colorado Boulder, Boulder, CO, 80309, USA
| | - J E Maclennan
- Department of Physics, University of Colorado Boulder, Boulder, CO, 80309, USA
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2
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Abstract
We demonstrate controlled material transport driven by temperature differences in thin freely suspended smectic films. Films with submicrometer thicknesses and lateral extensions of several millimeters were studied in microgravity during suborbital rocket flights. In-plane temperature differences cause two specific Marangoni effects, directed flow and convection patterns. At low gradients, practically thresholdless, flow transports material with a normal (negative) temperature coefficient of the surface tension dσ/dT<0 from the hot to the cold film edge, it accumulates at the cold film edge. In materials with dσ/dT>0, the reverse transport from the cold to the hot edge is observed. We present a model that describes the effect quantitatively. It predicts that not the temperature gradient in the film plane but the temperature difference between the thermopads is relevant for the effect.
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Affiliation(s)
- T Trittel
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany
| | - K Harth
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany
- Universiteit Twente, Physics of Fluids and Max Planck Center for Complex Fluid Dynamics, P.O. Box 217, 7500 AE Enschede, Netherlands
| | - C Klopp
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany
| | - R Stannarius
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany
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3
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Aumaître S, Behringer RP, Cazaubiel A, Clément E, Crassous J, Durian DJ, Falcon E, Fauve S, Fischer D, Garcimartín A, Garrabos Y, Hou M, Jia X, Lecoutre C, Luding S, Maza D, Noirhomme M, Opsomer E, Palencia F, Pöschel T, Schockmel J, Sperl M, Stannarius R, Vandewalle N, Yu P. An instrument for studying granular media in low-gravity environment. Rev Sci Instrum 2018; 89:075103. [PMID: 30068123 DOI: 10.1063/1.5034061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A new experimental facility has been designed and constructed to study driven granular media in a low-gravity environment. This versatile instrument, fully automatized, with a modular design based on several interchangeable experimental cells, allows us to investigate research topics ranging from dilute to dense regimes of granular media such as granular gas, segregation, convection, sound propagation, jamming, and rheology-all without the disturbance by gravitational stresses active on Earth. Here, we present the main parameters, protocols, and performance characteristics of the instrument. The current scientific objectives are then briefly described and, as a proof of concept, some first selected results obtained in low gravity during parabolic flight campaigns are presented.
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Affiliation(s)
- S Aumaître
- SPEC, DSM, CEA-Saclay, CNRS URA 2464, F-91191 Gif-sur-Yvette, France
| | - R P Behringer
- Department of Physics, Duke University, Durham, North Carolina 27708-0305, USA
| | - A Cazaubiel
- Université Paris Diderot, SPC, MSC, UMR 7057 CNRS, F-75013 Paris, France
| | - E Clément
- PMMH, ESPCI, UMR 7636 CNRS, F-75005 Paris, France
| | - J Crassous
- Université Rennes 1, IPR, UMR 6251 CNRS, F-35042 Rennes, France
| | - D J Durian
- University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396, USA
| | - E Falcon
- Université Paris Diderot, SPC, MSC, UMR 7057 CNRS, F-75013 Paris, France
| | - S Fauve
- École Normale Supérieure, LPS, CNRS, UMR 8550, F-75005 Paris, France
| | - D Fischer
- IEP, Otto von Guericke Universität, D-39106 Magdeburg, Germany
| | - A Garcimartín
- DFMA, Universidad de Navarra, E-31080 Pamplona, Spain
| | - Y Garrabos
- CNRS, ICMCB, Université de Bordeaux, UMR 5026, F-33600 Pessac, France
| | - M Hou
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - X Jia
- Institut Langevin, ESPCI Paris, PSL, CNRS, F-75005 Paris, France
| | - C Lecoutre
- CNRS, ICMCB, Université de Bordeaux, UMR 5026, F-33600 Pessac, France
| | - S Luding
- MSM, University of Twente, 7500 AE Enschede, The Netherlands
| | - D Maza
- DFMA, Universidad de Navarra, E-31080 Pamplona, Spain
| | - M Noirhomme
- GRASP, Institute of Physics B5a, University of Liège, B-4000 Liège, Belgium
| | - E Opsomer
- GRASP, Institute of Physics B5a, University of Liège, B-4000 Liège, Belgium
| | - F Palencia
- CNRS, ICMCB, Université de Bordeaux, UMR 5026, F-33600 Pessac, France
| | - T Pöschel
- Friedrich-Alexander Universität, IMS, D-91052 Erlangen, Germany
| | - J Schockmel
- GRASP, Institute of Physics B5a, University of Liège, B-4000 Liège, Belgium
| | - M Sperl
- Institut für Materialphysik im Weltraum, DLR, D-51170 Köln, Germany
| | - R Stannarius
- IEP, Otto von Guericke Universität, D-39106 Magdeburg, Germany
| | - N Vandewalle
- GRASP, Institute of Physics B5a, University of Liège, B-4000 Liège, Belgium
| | - P Yu
- MSM, University of Twente, 7500 AE Enschede, The Netherlands
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Ashour A, Wegner S, Trittel T, Börzsönyi T, Stannarius R. Outflow and clogging of shape-anisotropic grains in hoppers with small apertures. Soft Matter 2017; 13:402-414. [PMID: 27878164 DOI: 10.1039/c6sm02374f] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Outflow of granular material through a small orifice is a fundamental process in many industrial fields, for example in silo discharge, and in everyday's life. Most experimental studies of the dynamics have been performed so far with monodisperse disks in two-dimensional (2D) hoppers or spherical grains in 3D. We investigate this process for shape-anisotropic grains in 3D hoppers and discuss the role of size and shape parameters on avalanche statistics, clogging states, and mean flow velocities. It is shown that an increasing aspect ratio of the grains leads to lower flow rates and higher clogging probabilities compared to spherical grains. On the other hand, the number of grains forming the clog is larger for elongated grains of comparable volumes, and the long axis of these blocking grains is preferentially aligned towards the center of the orifice. We find a qualitative transition in the hopper discharge behavior for aspect ratios larger than ≈6. At still higher aspect ratios >8-12, the outflowing material leaves long vertical holes in the hopper that penetrate the complete granular bed. This changes the discharge characteristics qualitatively.
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Affiliation(s)
- A Ashour
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany. and Faculty of Engineering and Technology, Future University, End of 90 St., New Cairo, Egypt
| | - S Wegner
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany.
| | - T Trittel
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany.
| | - T Börzsönyi
- Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P. O. Box 49, H-1525 Budapest, Hungary
| | - R Stannarius
- Institute of Experimental Physics, Otto von Guericke University, 39106 Magdeburg, Germany.
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Abstract
Disclinations in liquid crystals bear striking analogies to defect structures in a wide variety of physical systems, and their straightforward optical observability makes them excellent models to study fundamental properties of defect interactions. We employ freely suspended smectic-C films, which behave as quasi-two-dimensional polar nematics. A procedure to capture high-strength disclinations in localized spots is introduced. These disclinations are released in a controlled way, and the motion of the mutually repelling topological charges with strength +1 is studied quantitatively. We demonstrate that the classical models, which employ elastic one-constant approximation, fail to describe their dynamics correctly. In realistic liquid crystals, even small differences between splay and bend constants lead to the selection of pure splay or pure bend +1 defects. For those, the models work only in very special configurations. In general, additional director walls are involved which reinforce the repulsive interactions substantially.
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Affiliation(s)
- R Stannarius
- Institute for Experimental Physics, Otto von Guericke University, D-39106 Magdeburg, Germany
| | - K Harth
- Institute for Experimental Physics, Otto von Guericke University, D-39106 Magdeburg, Germany
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6
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Salili SM, Ostapenko T, Kress O, Bailey C, Weissflog W, Harth K, Eremin A, Stannarius R, Jákli A. Rupture and recoil of bent-core liquid crystal filaments. Soft Matter 2016; 12:4725-4730. [PMID: 27140824 DOI: 10.1039/c6sm00290k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The recoil process of free-standing liquid crystal filaments is investigated experimentally and theoretically. We focus on two aspects, the contraction speed of the filament and a spontaneously formed undulation instability. At the moment of rupture, the filaments buckle similarly to the classical Euler buckling of elastic rods. The tip velocity decays with decreasing filament length. The wavelength of buckling affinely decreases with the retracting filament tip. The energy gain related to the decrease of the total length and surface area of the filaments is mainly dissipated by layer rearrangements during thickening of the fibre. A flow back into the meniscus is relevant only in the final stage of the recoil process. We introduce a model for the quantitative description of the filament retraction speed. The dynamics of this recoil behaviour may find relevance as a model for biology-related filaments.
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Affiliation(s)
- S M Salili
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA.
| | - T Ostapenko
- Institute of Experimental Physics, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany.
| | - O Kress
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA.
| | - C Bailey
- Leidos, 3745 Pentagon Blvd., Beavercreek, OH 45431, USA
| | - W Weissflog
- Martin Luther University Halle-Wittenberg, Department of Chemistry, Physical Chemistry, von-Danckelmann-Platz 4, 06120 Halle, Germany
| | - K Harth
- Institute of Experimental Physics, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany.
| | - A Eremin
- Institute of Experimental Physics, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany.
| | - R Stannarius
- Institute of Experimental Physics, Otto von Guericke University, Universitätsplatz 2, 39106 Magdeburg, Germany.
| | - A Jákli
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA.
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Kredentser S, Eremin A, Davidson P, Reshetnyak V, Stannarius R, Reznikov Y. Light-induced Soret effect and adsorption of nanocrystals in organic solvents. Eur Phys J E Soft Matter 2016; 39:38. [PMID: 27021655 DOI: 10.1140/epje/i2016-16038-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 01/21/2016] [Indexed: 06/05/2023]
Abstract
A light-induced Soret effect accompanied by photoinduced adsorption of pigment nanoparticles is described in organic solvents. We report an unexpected inversion of the nanoparticle flux which is directed along the temperarture gradient at short exposures to the light and switches against the gradient at longer exposures. This change of flux direction is due to light-induced adsorption of the nanocrystals onto the substrates of the cell.
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Affiliation(s)
- S Kredentser
- Institute of Physics of National Academy of Sciences of Ukraine, Pr. Nauky 46, 03028, Kyiv, Ukraine.
| | - A Eremin
- Otto-von-Guericke-Universität Magdeburg, 4120, Magdeburg, Germany
| | - P Davidson
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, 91405, Orsay, France
| | - V Reshetnyak
- Taras Shevchenko National University of Kyiv, 01601, Kyiv, Ukraine
| | - R Stannarius
- Otto-von-Guericke-Universität Magdeburg, 4120, Magdeburg, Germany
| | - Yu Reznikov
- Institute of Physics of National Academy of Sciences of Ukraine, Pr. Nauky 46, 03028, Kyiv, Ukraine
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Eremin A, Geng Y, Stannarius R, Ostapenko T, Challa PK, Gleeson JT, Jákli A, Klein S. Correction: Peculiarities of the magneto-optical response in dispersions of anisometric pigment nano-particles. RSC Adv 2016. [DOI: 10.1039/c6ra90089e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Correction for ‘Peculiarities of the magneto-optical response in dispersions of anisometric pigment nano-particles’ by A. Eremin et al., RSC Adv., 2016, 6, 80666–80669.
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Affiliation(s)
- A. Eremin
- Otto-von-Guericke-Universität Magdeburg
- FNW/IEP/ANP
- 39016 Magdeburg
- Germany
| | - Y. Geng
- Otto-von-Guericke-Universität Magdeburg
- FNW/IEP/ANP
- 39016 Magdeburg
- Germany
| | - R. Stannarius
- Otto-von-Guericke-Universität Magdeburg
- FNW/IEP/ANP
- 39016 Magdeburg
- Germany
| | - T. Ostapenko
- Max Planck Institute for Dynamics and Self-Organization (MPIDS)
- 37077 Göttingen
- Germany
| | - P. K. Challa
- Department of Physics
- Kent State University
- Kent
- USA
| | | | - A. Jákli
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - S. Klein
- HP Laboratories
- Bristol BS34 8QZ
- UK
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Sebastián N, Tamba MG, Stannarius R, de la Fuente MR, Salamonczyk M, Cukrov G, Gleeson J, Sprunt S, Jákli A, Welch C, Ahmed Z, Mehl GH, Eremin A. Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic–nematic transition. Phys Chem Chem Phys 2016; 18:19299-308. [DOI: 10.1039/c6cp03899a] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate a liquid crystal system exhibiting a variety of modulated structures on different length-scales: from helicoidal nematic to modulated smectic.
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10
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Eremin A, Geng Y, Stannarius R, Ostapenko T, Challa PK, Gleeson JT, Jákli A, Klein S. Peculiarities of the magneto-optical response in dispersions of anisometric pigment nano-particles. RSC Adv 2016. [DOI: 10.1039/c6ra12020b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We demonstrate an unusually strong magneto-optical response of elongated plate-shaped pigment particles in magnetic fields ranging from 0 to 25 T.
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Affiliation(s)
- A. Eremin
- Otto-von-Guericke-Universität Magdeburg
- FNW/IEP/ANP
- 39016 Magdeburg
- Germany
| | - Y. Geng
- Otto-von-Guericke-Universität Magdeburg
- FNW/IEP/ANP
- 39016 Magdeburg
- Germany
| | - R. Stannarius
- Otto-von-Guericke-Universität Magdeburg
- FNW/IEP/ANP
- 39016 Magdeburg
- Germany
| | - T. Ostapenko
- Max Planck Institute for Dynamics and Self-Organization (MPIDS)
- 37077 Göttingen
- Germany
| | - P. K. Challa
- Department of Physics
- Kent State University
- Kent
- USA
| | | | - A. Jákli
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - S. Klein
- HP Laboratories
- Bristol BS34 8QZ
- UK
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11
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Harth K, Mauney A, Stannarius R. Frustrated packing of spheres in a flat container under symmetry-breaking bias. Phys Rev E Stat Nonlin Soft Matter Phys 2015; 91:030201. [PMID: 25871031 DOI: 10.1103/physreve.91.030201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Indexed: 06/04/2023]
Abstract
We study statistical properties of packings of monodisperse spheres in a flat box. After "gravitational" filling and appropriate agitation, a nearly regular (in plane) but frustrated (normal to the plane) triangular lattice forms, where beads at individual sites touch either the front or back wall. It has striking analogies to order in antiferromagnetic Ising spin models. When tilting the container, Earth's gravitational field mimics external forces similar to magnetic fields in the spin systems. While packings in vertical containers adopt a frustrated state with statistical correlations between neighboring sites, the configurations continuously approach the predictions of a random Ising model when the cell tilt is increased. Our experiments offer insights into both the influence of geometrical constraints on random granular packing and a descriptive example of frustrated ordering.
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Affiliation(s)
- K Harth
- Institute for Experimental Physics, Otto von Guericke University, D-39106 Magdeburg, Germany
| | - A Mauney
- Institute for Experimental Physics, Otto von Guericke University, D-39106 Magdeburg, Germany
| | - R Stannarius
- Institute for Experimental Physics, Otto von Guericke University, D-39106 Magdeburg, Germany
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12
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Abstract
We demonstrate the nanostructure and filament formation of a novel liquid crystal phase of a dimeric mesogen below the twist–bend nematic phase.
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Affiliation(s)
- M. G. Tamba
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - S. M. Salili
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - C. Zhang
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - A. Jákli
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
| | - G. H. Mehl
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - R. Stannarius
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
| | - A. Eremin
- Department of Nonlinear Phenomena
- Institute for Experimental Physics
- Otto von Guericke University Magdeburg
- Magdeburg
- Germany
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Harth K, Kornek U, Trittel T, Strachauer U, Höme S, Will K, Stannarius R. Granular gases of rod-shaped grains in microgravity. Phys Rev Lett 2013; 110:144102. [PMID: 25166993 DOI: 10.1103/physrevlett.110.144102] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Indexed: 06/03/2023]
Abstract
Granular gases are convenient model systems to investigate the statistical physics of nonequilibrium systems. In the literature, one finds numerous theoretical predictions, but only few experiments. We study a weakly excited dilute gas of rods, confined in a cuboid container in microgravity during a suborbital rocket flight. With respect to a gas of spherical grains at comparable filling fraction, the mean free path is considerably reduced. This guarantees a dominance of grain-grain collisions over grain-wall collisions. No clustering was observed, unlike in similar experiments with spherical grains. Rod positions and orientations were determined and tracked. Translational and rotational velocity distributions are non-Gaussian. Equipartition of kinetic energy between translations and rotations is violated.
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Affiliation(s)
- K Harth
- Institute of Experimental Physics, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
| | - U Kornek
- Institute of Experimental Physics, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
| | - T Trittel
- Institute of Experimental Physics, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
| | - U Strachauer
- Institute of Experimental Physics, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
| | - S Höme
- Institute of Automation Engineering, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
| | - K Will
- Institute for Electronics, Signal Processing and Communications, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
| | - R Stannarius
- Institute of Experimental Physics, Otto-von-Guericke Universität Magdeburg, D-39016 Magdeburg, Germany
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14
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Stannarius R. Structures and properties of liquid crystals, by Lev M. Blinov. Liquid Crystals Today 2012. [DOI: 10.1080/1358314x.2012.773608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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15
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Morys M, Trittel T, Eremin A, Murphy P, Stannarius R. Tension of freely suspended fluid filaments. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 86:040501. [PMID: 23214519 DOI: 10.1103/physreve.86.040501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Indexed: 06/01/2023]
Abstract
Stable fluid filaments with diameters of several micrometers and slenderness ratios well above 1000 are unique objects formed by some liquid crystalline phases of bent-core mesogens. We present a technique to determine filament tensions from their deflection under defined loads. A strong temperature dependence is observed, with a minimum near the clearing temperature. Both the nonlinear relation between filament tension and diameter and the substantial increase of the tension with lower temperatures indicate contributions of volume terms, in addition to surface capillary forces. We discuss a model that relates these bulk terms to elastic forces, originating from the undulated smectic layer structure. This model can explain the origin of the filament stability.
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Affiliation(s)
- M Morys
- Otto von Guericke University Magdeburg, Institute of Experimental Physics, Universitätsplatz 2, D-39106 Magdeburg, Germany
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16
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Eremin A, Baumgarten S, Harth K, Stannarius R, Nguyen ZH, Goldfain A, Park CS, Maclennan JE, Glaser MA, Clark NA. Two-dimensional microrheology of freely suspended liquid crystal films. Phys Rev Lett 2011; 107:268301. [PMID: 22243186 DOI: 10.1103/physrevlett.107.268301] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 08/21/2011] [Indexed: 05/31/2023]
Abstract
Smectic liquid crystals form freely-suspended, fluid films of highly uniform structure and thickness, making them ideal systems for studies of hydrodynamics in two dimensions. We have measured particle mobility and shear viscosity by direct observation of the gravitational drift of silica spheres and smectic islands included in these fluid membranes. In thick films, we observe a hydrodynamic regime dominated by lateral confinement effects, with the mobility of the inclusion determined predominantly by coupling of the fluid flow to the fixed boundaries of the film. In thin films, the mobility of inclusions is governed primarily by coupling of the fluid to the surrounding air, as predicted by Saffman-Delbrück theory.
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Affiliation(s)
- A Eremin
- Otto-von-Guericke Universität Magdeburg, Institute for Experimental Physics, D-39016 Magdeburg, Germany
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17
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Weissflog W, Pelzl G, Kresse H, Baumeister U, Brand K, Schröder MW, Tamba MG, Findeisen-Tandel S, Kornek U, Stern S, Eremin A, Stannarius R, Svoboda J. In search of a new design strategy for solid single-component organic ferroelectrics: Polar crystalline phases formed by bent-core molecules. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/c0jm00322k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Harth K, Stannarius R. Corona patterns around inclusions in freely suspended smectic films. Eur Phys J E Soft Matter 2009; 28:265-272. [PMID: 19169722 DOI: 10.1140/epje/i2008-10404-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Accepted: 12/10/2008] [Indexed: 05/27/2023]
Abstract
We discuss the structure and physical origin of corona patterns observed around solid or liquid spherical inclusions in freely suspended smectic films. Such patterns are observed when droplets or solid beads of micrometer size are sprayed onto the films. They are found in the smectic C phase and in the smectic A phase above such a smectic C phase, but disappear, for example, at the transition into a lower-temperature smectic B phase. We show that these structures are equivalent to splay domains found in the meniscus of freely suspended films, originating from surface-induced spontaneous splay.
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Affiliation(s)
- K Harth
- Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany.
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19
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Findeisen-Tandel S, Schröder MW, Pelzl G, Baumeister U, Weissflog W, Stern S, Nemes A, Stannarius R, Eremin A. Multistage polar switching in bent-core mesogens. Eur Phys J E Soft Matter 2008; 25:395-402. [PMID: 18425409 DOI: 10.1140/epje/i2007-10306-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 02/27/2008] [Indexed: 05/26/2023]
Abstract
We report a novel type of electro-optical switching in a tilted smectic phase of bent-shaped mesogens. The switching consists of a continuous stage and two bistable transitions. Detailed optical and electro-optical measurements using high-speed imaging are given and possible interpretations of the experimental results are discussed.
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Affiliation(s)
- S Findeisen-Tandel
- Martin-Luther-Universität Halle-Wittenberg, Institut für Physikalische Chemie, Halle (Saale), Germany
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20
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Stannarius R, Eremin A, Tamba MG, Pelzl G, Weissflog W. Field-induced texture transitions in a bent-core nematic liquid crystal. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 76:061704. [PMID: 18233858 DOI: 10.1103/physreve.76.061704] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2006] [Revised: 11/02/2007] [Indexed: 05/25/2023]
Abstract
It is demonstrated in electro-optic experiments that an external electric field of the order of 10;{5} V/m induces persisting texture transitions in a nematic phase formed by bent-core mesogens. The field-induced metastable state is identified by its optical and electric properties. After the field is switched off, the original and induced states can coexist in domains for about one hour in planar sandwich cells. During this time, the induced domains gradually shrink but they can be stabilized in moderate electric fields. The occurrence of similar domains in homeotropic cells suggests that the transition into a metastable biaxial state is observed. In the field-free planar ground state, the formation of inversion walls is observed inside the metastable domains.
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Affiliation(s)
- R Stannarius
- Institute of Experimental Physics, Otto-von-Guericke-University, Universitätsplatz 2, D-39106 Magdeburg, Germany
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21
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Stannarius R, Heuer J. Electroconvection in nematics above the splay Fréedericksz transition. Eur Phys J E Soft Matter 2007; 24:27-33. [PMID: 17767374 DOI: 10.1140/epje/i2007-10207-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 07/12/2007] [Indexed: 05/17/2023]
Abstract
We present a basic model for an instability leading to a novel type of electroconvection patterns observed above the splay Fréedericksz transition in nematics. Such patterns, with wave vector perpendicular to the director easy axis, are found in planar sandwich cells under crossed polarizers, they do not produce shadowgraph images at onset. An adaptation of the classical Carr Helfrich mechanism is introduced. The ground state is a tilted director field uniform in the cell plane. The proposed mechanism destabilizes this director field and leads to a structure with modulated out-of-plane (twist) deformations. Experimental confirmation is provided by polarizing microscopy. All experimental observations are qualitatively explained with the proposed model.
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Affiliation(s)
- R Stannarius
- Otto-von-Guericke Universität Magdeburg, Institut für Experimentelle Physik, D-39106 Magdeburg, Germany.
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22
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Bohley C, Stannarius R. Colloidal inclusions in smectic films with spontaneous bend. Eur Phys J E Soft Matter 2007; 23:25-30. [PMID: 17510750 DOI: 10.1140/epje/i2007-10172-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Accepted: 04/24/2007] [Indexed: 05/15/2023]
Abstract
Inclusions in free-standing smectic films are simple model systems for two-dimensional anisotropic dispersions. From theory and experiment, different topologies of elastic distortions of the embedding liquid crystal are known. Quadrupolar and different dipolar defect configurations in the vicinity of the inclusion are possible, and these configurations determine the type of interactions between the inclusions. The quadrupolar configuration is often energetically preferred. We show, however, that dipolar director configurations around inclusions can be energetically favourable over quadrupolar arrangements in chiral smectics, as a consequence of a spontaneous-bend term in the elastic-energy formulation. As the inclusion size influences the selection of the deformation types, the corresponding spontaneous-bend constant can be estimated for the strong anchoring limit if the c -director fields around inclusions of different diameters are taken into account.
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Affiliation(s)
- C Bohley
- Institute of Experimental Physics, Nonlinear Phenomena, Universitätsplatz 2, D-39016 Magdeburg, Germany.
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23
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Tamba MG, Weissflog W, Eremin A, Heuer J, Stannarius R. Electro-optic characterization of a nematic phase formed by bent core mesogens. Eur Phys J E Soft Matter 2007; 22:85-95. [PMID: 17334690 DOI: 10.1140/epje/e2007-00015-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2006] [Indexed: 05/14/2023]
Abstract
The purpose of this paper is the demonstration that bent core nematic phases behave quantitatively and qualitatively very different from ordinary calamitic nematics in their electro-optical characteristics. We present measurements of the elastic properties from the analysis of Brochard-Leger walls that are formed during the splay Fréedericksz transition in sandwich cells. These walls possess an unusually large shape anisotropy as compared to similar structures in calamitic nematics. The wall shapes can be explained when one assumes that the bend elastic constant K(33) is one order of magnitude larger than the twist constant K(22) of the material, supposing that flexoelectricity in the description of the elastic deformations can be neglected. Further we report periodic structures above the splay Fréedericksz transition with a wave vector perpendicular to the director easy axis. They represent either a static instability or an unconventional type of electrically driven convection.
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Affiliation(s)
- M-G Tamba
- Martin-Luther-University Halle, Institute of Physical Chemistry, Mühlpforte 1, 06108, Halle, Germany
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24
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Affiliation(s)
- H. Amm
- a Universität Leipzig, Fakultät für Physik , Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - U. Behn
- a Universität Leipzig, Fakultät für Physik , Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - Th. John
- a Universität Leipzig, Fakultät für Physik , Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - R. Stannarius
- a Universität Leipzig, Fakultät für Physik , Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
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25
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Affiliation(s)
- Ch. Cramer
- a Universität Leipzig , Fakultät für Physik und Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - Th. Cramer
- a Universität Leipzig , Fakultät für Physik und Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - M. Arndt
- a Universität Leipzig , Fakultät für Physik und Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - F. Kremer
- a Universität Leipzig , Fakultät für Physik und Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - L. Naji
- a Universität Leipzig , Fakultät für Physik und Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
| | - R. Stannarius
- a Universität Leipzig , Fakultät für Physik und Geowissenschaften Linnéstr. 5, Leipzig , 04103 , Germany
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26
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Affiliation(s)
- J. Birnstock
- a Universittät Leipzig, Institut für Experimentalphysik I , Linnéstrasse 5, D-04103, Leipzig
| | - R. Stannarius
- a Universittät Leipzig, Institut für Experimentalphysik I , Linnéstrasse 5, D-04103, Leipzig
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27
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Affiliation(s)
- R. Stannarius
- a Universität Leipzig, Institut für Experimentalphysik I , Linnéstrasse 5, D-04103 , Leipzig
| | - H. Schüring
- a Universität Leipzig, Institut für Experimentalphysik I , Linnéstrasse 5, D-04103 , Leipzig
| | - C. Tolksdorf
- b Universität Mainz, FB19- Organisch-chemisches Institut , Duesbergweg 10-14, D-55099 , Mainz
| | - R. Zentel
- b Universität Mainz, FB19- Organisch-chemisches Institut , Duesbergweg 10-14, D-55099 , Mainz
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28
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Affiliation(s)
- R. Stannarius
- a Universität Leipzig, Fakultät für Physik und Geowissenschaften , Linnéstr. 5, Leipzig , 04103 , Germany
| | - C. Cramer
- b University of Delaware , Newark , DE , 19716 , USA
| | - H. Schüring
- a Universität Leipzig, Fakultät für Physik und Geowissenschaften , Linnéstr. 5, Leipzig , 04103 , Germany
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29
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Affiliation(s)
- S. A. Rozanski
- a Maria Sklodowska-Curie High School , W. Pola 11, 64‐920 , Pila , Poland
| | - L. Naji
- b Universität Leipzig, Fakultät für Physik und Geowissenschaften , Linnéstr. 5, D-04103 , Leipzig , Germany
| | - F. Kremer
- b Universität Leipzig, Fakultät für Physik und Geowissenschaften , Linnéstr. 5, D-04103 , Leipzig , Germany
| | - R. Stannarius
- b Universität Leipzig, Fakultät für Physik und Geowissenschaften , Linnéstr. 5, D-04103 , Leipzig , Germany
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30
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Eremin A, Bohley C, Stannarius R. c-director relaxation around a vortex of strength +1 in free-standing smectic-C films. Eur Phys J E Soft Matter 2006; 21:57-67. [PMID: 17093894 DOI: 10.1140/epje/i2006-10046-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Accepted: 10/02/2006] [Indexed: 05/12/2023]
Abstract
The relaxation of director fields in freely suspended smectic films is studied experimentally by means of polarizing microscopy, and analyzed by solving the torque balance equation under appropriate initial and boundary conditions. We consider in particular the role of anchoring conditions of the c-director at particles and defects in the film. The structure of regular relaxation patterns allows to determine the elastic anisotropy of smectic materials. The splay elastic constant can exceed the bend constant by a factor of two and more. A remarkable consequence of this anisotropy is the stick-slip-like relaxation around a central defect of topological strength s = + 1.
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Affiliation(s)
- A Eremin
- Institut für Experimentelle Physik, Otto-von-Guericke-Universität, Universitätsplatz 2, D-39106, Magdeburg, Germany.
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31
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Bohley C, Stannarius R. Energetics of 2D colloids in free-standing smectic-C films. Eur Phys J E Soft Matter 2006; 20:299-308. [PMID: 16858514 DOI: 10.1140/epje/i2006-10019-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Accepted: 06/29/2006] [Indexed: 05/10/2023]
Abstract
The formation of regular colloid patterns in free-standing smectic films at the transition from the smectic-C to the isotropic or nematic phase is well known experimentally. The self-organization of isotropic or nematic droplets is caused by their mutual interaction, mediated by elastic distortions of the local director in the surrounding liquid crystal. These distortions are related to the anchoring conditions of the director at the droplet border. We describe analytically the energetics of the liquid crystal environment of a single droplet in one-constant approximation. A method of complex analysis, Conformal Mapping, is employed. Following a suggestion of Dolganov et al. (Phys. Rev. E. 73, 041706 (2006)), energetics of chain and grid patterns built from the colloids are investigated numerically in order to explain experimentally observed formations and their director fields.
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Affiliation(s)
- C Bohley
- Institute of Experimental Physics, Nonlinear Phenomena, Universitätsplatz 2, D-39016, Magdeburg, Germany.
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32
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Stannarius R, Aksenov V, Bläsing J, Krost A, Rössle M, Zentel R. Mechanical manipulation of molecular lattice parameters in smectic elastomers. Phys Chem Chem Phys 2006; 8:2293-8. [PMID: 16688312 DOI: 10.1039/b600839a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Smectic liquid crystalline elastomers (SLCE) represent unique materials that combine a 1-D molecular lattice arrangement and orientational order with rubber-elasticity mediated by a polymer network. Such materials may exhibit large thermo-mechanical, opto-mechanical and electro-mechanical effects, due to the coupling of macroscopic sample geometry and microscopic structural features. It is shown that the molecular layer dimensions in the smectic phases can be influenced reversibly by macroscopic strain of the material. We present a microscopic model on the basis of experimental results obtained by mechanical dilatation measurements, optical interferometry, X-ray scattering, (13)C NMR, FTIR and polarizing microscopy data. The model gives an explanation of the controversial results obtained in different types of smectic elastomers.
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Affiliation(s)
- R Stannarius
- Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, Germany.
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33
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Völtz C, Stannarius R. Buckling instability of droplet chains in freely suspended smectic films. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:011705. [PMID: 16089985 DOI: 10.1103/physreve.72.011705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Indexed: 05/03/2023]
Abstract
A buckling instability of chains of isotropic droplets in smectic films is investigated. The c -director field in a free-standing film is prepared as a target pattern with a continuous radial deformation. In such a pattern, isotropic liquid droplets are induced by light irradiation of the photochromic mesogenic material. The droplets align tangentially in regular chains in the regular structure of the c -director field. Incorporation of additional droplets lengthens the chains at a given ring diameter until they form complete rings. Further chain growth introduces a reversible buckling with a characteristic wave length. The phenomenon is similar in many respects to growth processes in biosystems or Euler buckling in polymer foils. A simple model of the wavelength selection mechanism is introduced.
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Affiliation(s)
- C Völtz
- Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, Germany
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34
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Völtz C, Stannarius R. Self-organization of isotropic droplets in smectic- C free-standing films. Phys Rev E Stat Nonlin Soft Matter Phys 2004; 70:061702. [PMID: 15697385 DOI: 10.1103/physreve.70.061702] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Indexed: 05/24/2023]
Abstract
Free standing smectic films have been investigated at the transition from the smectic- C phase to the isotropic phase. In the vicinity of the bulk transition temperatures, isotropic droplets of micrometer size appear in the film. Such systems represent convenient models for anisotropic, two-dimensional emulsions. A characteristic feature of the droplets is their mutual interaction by elastic distortions of the local orientation of the film, the c director, which are related to the anchoring conditions of the c director at the droplet border. We describe in detail the director deformations created by isotropic droplets of different sizes, and their role in the spontaneous organization of regular droplet patterns. Depending upon droplet size and anchoring strength, topological defects can be induced in the c -director field. Qualitative differences to literature data on cholesteric droplets in smectic- C* films are discussed.
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Affiliation(s)
- C Völtz
- Otto-von-Guericke-Universität Magdeburg, Institut für Experimentelle Physik, D-39106 Magdeburg, Germany.
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35
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Grigutsch M, Stannarius R. Stripe patterns in the magnetic reorientation of a glass-forming nematic liquid crystal. Eur Phys J E Soft Matter 2002; 8:365-372. [PMID: 15010937 DOI: 10.1140/epje/i2001-10107-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We study spontaneous pattern formation in a glass-forming nematic liquid crystal during the magnetically induced dynamic Fréedericksz transition. Pattern growth rates and wavelengths as functions of the magnetic field are extracted from optical transmission textures of thin planar cells. The characteristics of the observed stripe pattern can be related to viscoelastic parameters of the nematic by means of a linear stability analysis of director fluctuation modes. The viscous properties of the material allow to vary the time scales of the experiment with temperature by orders of magnitude, leaving the spatial structure of the pattern essentially unchanged. We find that the ratios of shear and rotational viscosity coefficients relevant for the pattern wavelength selection remain constant in the temperature range investigated, whereas their absolute values change by almost two orders.
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Affiliation(s)
- M Grigutsch
- Universität Leipzig, Institut für Experimentelle Physik I, Leipzig, Germany
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36
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Stannarius R, Köhler R, Dietrich U, Lösche M, Tolksdorf C, Zentel R. Structure and elastic properties of smectic liquid crystalline elastomer films. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 65:041707. [PMID: 12005846 DOI: 10.1103/physreve.65.041707] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2001] [Indexed: 05/23/2023]
Abstract
Mechanical measurements, x-ray investigations, and optical microscopy are employed to characterize the interplay of chemical composition, network topology, and elastic response of smectic liquid crystalline elastomers (LCEs) in various mesophases. Macroscopically ordered elastomer films of submicrometer thicknesses were prepared by cross linking freely suspended smectic polymer films. The cross-linked material preserves the mesomorphism and phase transitions of the precursor polymer. The elastic response of the smectic LCE is entropic, and the corresponding elastic moduli are of the order of MPa. In the tilted ferroelectric smectic-C* phase, the network structure plays an important role. Due to the coupling of elastic network deformations to the orientation of the mesogenic groups in interlayer cross-linked materials (mesogenic cross-linker units), the stress-strain characteristics is found to differ qualitatively from that in the other phases.
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Affiliation(s)
- R Stannarius
- Institut für Experimentalphysik I, Universität Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany
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37
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Stannarius R, Birnstock J. Comment on "double diffusive convection in freely suspended soap films". Phys Rev Lett 2001; 86:4187-4188. [PMID: 11328127 DOI: 10.1103/physrevlett.86.4187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2000] [Indexed: 05/23/2023]
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38
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Bohatsch H, Stannarius R. Frequency-induced structure transition of nematic electroconvection in twist cells. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:5591-9. [PMID: 11970436 DOI: 10.1103/physreve.60.5591] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/1998] [Revised: 05/14/1999] [Indexed: 04/18/2023]
Abstract
We investigate electroconvection of nematic liquid crystals in planar 90 degrees twist cells in the dielectric regime. These cells provide competing boundary conditions for the nematic director at both electrodes. When the ratio of cell gap and roll width is not too small (in thin cells and at low frequencies), the convection rolls form along the director in the cell middle, which is diagonal to the anchoring directions. This is in accordance with known behavior in the conduction regime and with the assumption of a bulk instability (rolls traversing the cell). When the ratio of roll periodicity to cell gap is very small in the high-frequency range and the thick cells, a regular convection pattern sets in with wave vectors directed along the two alignment directions. We suggest the interpretation that two independent systems of convection rolls form localized near the electrode plates. It is very likely that a similar behavior occurs in nontwisted cells where it is difficult to identify experimentally.
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Affiliation(s)
- H Bohatsch
- Fakultät für Physik und Geowissenschaften, Universität Leipzig, Linnéstrasse 5, D-04103 Leipzig, Germany
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39
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Grigutsch M, Stannarius R. Comment on "Corresponding states of periodic structures in nematic liquid crystals". Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:1092-5; author reply 1096-8. [PMID: 11969862 DOI: 10.1103/physreve.60.1092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/1998] [Indexed: 04/18/2023]
Abstract
Palangana, Simões, Evangelista, and Arrotéia [Phys. Rev. E 56, 4282 (1997)] (PSEA) propose a general scaling model for periodic wall patterns in the magnetic twist Fréedericksz transition of nematics, performing an elastic energy analysis. We demonstrate that this model is incorrect because it does not consider consistently the hydrodynamic wavelength selection of the observed structures, but is based on the assumption of inappropriate model functions instead. It is shown that experimental data actually contradict the proposed theory. The approach of PSEA is particularly not suited to determine elastic constant ratios of nematic liquid crystals.
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Fleischer G, Voigt-Martin I, Kremer F, Kratochvíl P, Blümich B, Huwe A, Klöpper N, Fischer T, Stannarius R, Klöpper N, Pfeifer H. Book reviews. Colloid Polym Sci 1997. [DOI: 10.1007/bf03035218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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41
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Cramer C, Cramer T, Kremer F, Stannarius R. Measurement of orientational order and mobility of a nematic liquid crystal in random nanometer confinement. J Chem Phys 1997. [DOI: 10.1063/1.473425] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Arndt M, Stannarius R, Gorbatschow W, Kremer F. Dielectric investigations of the dynamic glass transition in nanopores. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 54:5377-5390. [PMID: 9965723 DOI: 10.1103/physreve.54.5377] [Citation(s) in RCA: 198] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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44
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Fischer T, Stannarius R, Boehnke UC, Kremer F, Shilov S. Book reviews. Colloid Polym Sci 1996. [DOI: 10.1007/bf00654678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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45
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Schäfer H, Sternin E, Stannarius R, Arndt M, Kremer F. Novel approach to the analysis of broadband dielectric spectra. Phys Rev Lett 1996; 76:2177-2180. [PMID: 10060625 DOI: 10.1103/physrevlett.76.2177] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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46
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47
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Schmiedel H, Stannarius R, Feller G, Cramer C. Induction of a Tilted Chiral Structure in Micro-confined Cholesteric Liquid Crystals. Z PHYS CHEM 1995. [DOI: 10.1524/zpch.1995.190.part_1.135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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48
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Grigutsch M, Klöpper N, Schmiedel H, Stannarius R. Transient structures in the twist Fréedericksz transition of low-molecular-weight nematic liquid crystals. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1994; 49:5452-5461. [PMID: 9961872 DOI: 10.1103/physreve.49.5452] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Crawford GP, Stannarius R, Doane JW. Surface-induced orientational order in the isotropic phase of a liquid-crystal material. Phys Rev A 1991; 44:2558-2569. [PMID: 9906236 DOI: 10.1103/physreva.44.2558] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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