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Rudyak VY, Krakhalev MN, Gardymova AP, Abdullaev AS, Alekseev AA, Zyryanov VY. Effect of elastic constants on electrically induced transition in twisted radial cholesteric droplets. Sci Rep 2022; 12:9565. [PMID: 35688866 PMCID: PMC9187752 DOI: 10.1038/s41598-022-13612-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 05/10/2022] [Indexed: 11/09/2022] Open
Abstract
In this work, we investigated the behavior of cholesteric droplets with homeotropic boundary conditions experimentally and by computer simulations. Small droplets forming twisted radial structures were studied. We obtained two different paths of structural transformations under electric field in such droplets. The choice between these paths has probabilistic nature. The ratio between the two transition types was found to be sensitive to the elastic constants of LC forming the droplet. We suggest the principal approach for in situ estimation of ratios between elastic constants in cholesteric LCs deposited in polymer-dispersed LC material and discuss its strong and weak sides.
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Affiliation(s)
- Vladimir Yu Rudyak
- Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia, 119991.
| | - Mikhail N Krakhalev
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia, 660036.,Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russia, 660041
| | - Anna P Gardymova
- Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russia, 660041
| | - Abylgazy S Abdullaev
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia, 660036.,Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk, Russia, 660041
| | - Andrey A Alekseev
- Faculty of Physics, Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Victor Ya Zyryanov
- Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia, 660036
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Senyuk B, Mozaffari A, Crust K, Zhang R, de Pablo JJ, Smalyukh II. Transformation between elastic dipoles, quadrupoles, octupoles, and hexadecapoles driven by surfactant self-assembly in nematic emulsion. SCIENCE ADVANCES 2021; 7:7/25/eabg0377. [PMID: 34144988 PMCID: PMC8213233 DOI: 10.1126/sciadv.abg0377] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
Emulsions comprising isotropic fluid drops within a nematic host are of interest for applications ranging from biodetection to smart windows, which rely on changes of molecular alignment structures around the drops in response to chemical, thermal, electric, and other stimuli. We show that absorption or desorption of trace amounts of common surfactants can drive continuous transformations of elastic multipoles induced by the droplets within the uniformly aligned nematic host. Out-of-equilibrium dynamics of director structures emerge from a controlled self-assembly or desorption of different surfactants at the drop-nematic interfaces, with ensuing forward and reverse transformations between elastic dipoles, quadrupoles, octupoles, and hexadecapoles. We characterize intertransformations of droplet-induced surface and bulk defects, probe elastic pair interactions, and discuss emergent prospects for fundamental science and applications of the reconfigurable nematic emulsions.
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Affiliation(s)
- Bohdan Senyuk
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO 80309, USA
| | - Ali Mozaffari
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
| | - Kevin Crust
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO 80309, USA
| | - Rui Zhang
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR
| | - Juan J de Pablo
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
- Center for Molecular Engineering, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Ivan I Smalyukh
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, CO 80309, USA.
- Department of Electrical, Computer, and Energy Engineering and Materials Science and Engineering Program, University of Colorado, Boulder, CO 80309, USA
- Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado, Boulder, CO 80309, USA
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Benyettou F, Zheng X, Elacqua E, Wang Y, Dalvand P, Asfari Z, Olsen JC, Han DS, Saleh N, Elhabiri M, Weck M, Trabolsi A. Redox-Responsive Viologen-Mediated Self-Assembly of CB[7]-Modified Patchy Particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:7144-7150. [PMID: 27323835 DOI: 10.1021/acs.langmuir.6b01433] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Sulfonated surface patches of poly(styrene)-based colloidal particles (CPs) were functionalized with cucurbit[7]uril (CB[7]). The macrocycles served as recognition units for diphenyl viologen (DPV(2+)), a rigid bridging ligand. The addition of DPV(2+) to aqueous suspensions of the particles triggered the self-assembly of short linear and branched chainlike structures. The self-assembly mechanism is based on hydrophobic/ion-charge interactions that are established between DPV(2+) and surface-adsorbed CB[7]. DPV(2+) guides the self-assembly of the CPs by forming a ternary DPV(2+)⊂(CB[7])2 complex in which the two CB[7] macrocycles are attached to two different particles. Viologen-driven particle assembly was found to be both directional and reversible. Whereas sodium chloride triggers irreversible particle disassembly, the one-electron reduction of DPV(2+) with sodium dithionite causes disassembly that can be reversed via air oxidation. Thus, this bottom-up synthetic supramolecular approach allowed for the reversible formation and directional alignment of a 2D colloidal material.
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Affiliation(s)
- Farah Benyettou
- New York University Abu Dhabi , Abu Dhabi, United Arab Emirates
| | - Xiaolong Zheng
- Molecular Design Institute and Department of Chemistry, New York University , New York, New York 10003, United States
| | - Elizabeth Elacqua
- Molecular Design Institute and Department of Chemistry, New York University , New York, New York 10003, United States
| | - Yu Wang
- Molecular Design Institute and Department of Chemistry, New York University , New York, New York 10003, United States
| | - Parastoo Dalvand
- Laboratoire de Chimie Bioorganique et Médicinale, UMR 7509 CNRS, Université de Strasbourg, ECPM , Strasbourg, France
| | - Zouhair Asfari
- Laboratoire d'Ingénierie Moléculaire Appliquée à l'Analyse, IPHC, UMR 7178 CNRS, Université de Strasbourg, ECPM , 25 rue Becquerel, 67200 Strasbourg, France
| | - John-Carl Olsen
- School of Sciences, Indiana University Kokomo , Kokomo, Indiana 46904, United States
| | - Dong Suk Han
- Chemical Engineering Program, Texas A&M University at Qatar, Education City , Doha, Qatar
| | - Na'il Saleh
- College of Science, Department of Chemistry, United Arab Emirates University , Al-Ain, United Arab Emirates
| | - Mourad Elhabiri
- Laboratoire de Chimie Bioorganique et Médicinale, UMR 7509 CNRS, Université de Strasbourg, ECPM , Strasbourg, France
| | - Marcus Weck
- Molecular Design Institute and Department of Chemistry, New York University , New York, New York 10003, United States
| | - Ali Trabolsi
- New York University Abu Dhabi , Abu Dhabi, United Arab Emirates
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Kos Ž, Ravnik M. Relevance of saddle-splay elasticity in complex nematic geometries. SOFT MATTER 2016; 12:1313-1323. [PMID: 26610395 DOI: 10.1039/c5sm02417j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate the relevance of saddle-splay elasticity in nematic liquid crystalline fluids in the context of complex surface anchoring conditions and the complex geometrical confinement. Specifically, nematic cells with patterns of surface anchoring and colloidal knots are shown as examples where saddle-splay free energy contribution can have a notable role which originates from nonhomogeneous surface anchoring and the varying surface curvature. Patterned nematic cells are shown to exhibit various (meta)stable configurations of nematic field, with relative (meta)stability depending on the saddle-splay. We show that for high enough values of saddle-splay elastic constant K24 a previously unstable conformation can be stabilised, more generally indicating that the saddle-splay can reverse or change the (meta)stability of various nematic structures affecting their phase diagrams. Furthermore, we investigate saddle-splay elasticity in the geometry of highly curved boundaries - the colloidal particle knots in nematic - where the local curvature of the particles induces complex spatial variations of the saddle-splay contributions. Finally, a nematic order parameter tensor based saddle-splay invariant is shown, which allows for the direct calculation of saddle-splay free energy from the Q-tensor, a possibility very relevant for multiple mesoscopic modelling approaches, such as Landau-de Gennes free energy modelling.
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Affiliation(s)
- Žiga Kos
- Faculty of Mathematics and Physics, University of Ljubljana, Slovenia.
| | - Miha Ravnik
- Faculty of Mathematics and Physics, University of Ljubljana, Slovenia. and Josef Stefan Institute, Ljubljana, Slovenia
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Cattaneo L, Kos Ž, Savoini M, Kouwer P, Rowan A, Ravnik M, Muševič I, Rasing T. Electric field generation of Skyrmion-like structures in a nematic liquid crystal. SOFT MATTER 2016; 12:853-8. [PMID: 26549212 PMCID: PMC5299589 DOI: 10.1039/c5sm01726b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 10/30/2015] [Indexed: 06/05/2023]
Abstract
Skyrmions are particle-like topological objects that are increasingly drawing attention in condensed matter physics, where they are connected to inversion symmetry breaking and chirality. Here we report the generation of stable Skyrmion-like structures in a thin nematic liquid crystal film on chemically patterned patchy surfaces. Using the interplay of material elasticity and surface boundary conditions, we use a strong electric field to quench the nematic liquid crystal from a fully aligned phase to vortex-like nematic liquid crystal structures, centered on patterned patches, which carry two different sorts of topological defects. Numerical calculations reveal that these are Skyrmion-like structures, seeded from the surface boojum topological defects and swirling towards the second confining surface. These observations, supported by numerical methods, demonstrate the possibility to generate, manipulate and study Skyrmion-like objects in nematic liquid crystals on patterned surfaces.
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Affiliation(s)
- Laura Cattaneo
- Radboud University, Institute of Molecules and Materials (IMM), Heyendaalseweg 135, 6525 AJ, Nijmegen, Netherlands
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Rudyak VY, Emelyanenko AV. Orientational ordering of Janus colloids in cholesteric liquid crystals. SOFT MATTER 2015; 11:7237-7240. [PMID: 26291514 DOI: 10.1039/c5sm01784j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In this paper we show that Janus colloids, which are spherical particles with hybrid anchoring conditions, have preferable orientations in cholesteric media depending on the cholesteric wave vector. Simulations reveal that the tilt angle of a particle varies greatly with variation of the particle diameter to the cholesteric pitch ratio, which makes it possible to stabilize the appropriate particle orientation and to control it by variation of the cholesteric pitch.
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Beller DA, Gharbi MA, Liu IB. Shape-controlled orientation and assembly of colloids with sharp edges in nematic liquid crystals. SOFT MATTER 2015; 11:1078-1086. [PMID: 25523158 DOI: 10.1039/c4sm01910e] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The assembly of colloids in nematic liquid crystals via topological defects has been extensively studied for spherical particles, and investigations of other colloid shapes have revealed a wide array of new assembly behaviors. We show, using Landau-de Gennes numerical modeling, that nematic defect configurations and colloidal assembly can be strongly influenced by fine details of colloid shape, in particular the presence of sharp edges. For cylinder, microbullet, and cube colloid geometries, we obtain the particles' equilibrium alignment directions and effective pair interaction potentials as a function of simple shape parameters. We find that defects pin at sharp edges, and that the colloid consequently orients at an oblique angle relative to the far-field nematic director that depends on the colloid's shape. This shape-dependent alignment, which we confirm in experimental measurements, raises the possibility of selecting self-assembly outcomes for colloids in liquid crystals by tuning particle geometry.
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Affiliation(s)
- Daniel A Beller
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
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