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Emelyanenko AV, Rudyak VY, Shvetsov SA, Araoka F, Nishikawa H, Ishikawa K. Emergence of paraelectric, improper antiferroelectric, and proper ferroelectric nematic phases in a liquid crystal composed of polar molecules. Phys Rev E 2022; 105:064701. [PMID: 35854528 DOI: 10.1103/physreve.105.064701] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 05/13/2022] [Indexed: 05/15/2023]
Abstract
We have elaborated a theoretical approach for the description of polar nematic phases observed by Nishikawa et al. [Adv. Mater. 29, 1702354 (2017)0935-964810.1002/adma.201702354], their structures, and transitions between them. Specific symmetry contributions to the pair molecular potentials provide the molecular mechanisms responsible for the formation of proper and improper polarity on the macroscopic level. An improper antiferroelectric nematic M2 phase can arise between paraelectric nematic M1 and proper ferroelectric nematic MP in the temperature scale. The local polarization in M2 arises mostly due to the local splay deformation. The director distribution in M2 represents the conjugation of cylindrical waves with opposite splay and polarization signs. The director and polarization are parallel to the cylindrical domain axes in the middle of each cylinder but exhibit considerable (mostly radial) deformation on the periphery of each cylinder. Polarization vectors are mostly stacked antiparallel on the borders between the domains without the director disruption. The domain size decreases with the decreasing temperature, the percentage of the antiferroelectric decouplings increases, and M2 exhibits the first-order phase transition into proper ferroelectric MP. With the increasing temperature the domain size in the M2 phase increases, the domination of particular polar orientation of molecules reduces, and finally, the domain size diverges at particular temperature corresponding to the second-order phase transition from M2 to paraelectric M1. Variations of the polar and nonpolar orientational order parameters are estimated within each phase and between the phases. Our experimental and computer simulation results (also presented in the paper) fully support our theoretical findings.
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Affiliation(s)
| | - V Yu Rudyak
- Lomonosov Moscow State University, Moscow 119991, Russia
| | - S A Shvetsov
- Lomonosov Moscow State University, Moscow 119991, Russia
- Lebedev Physical Institute, Moscow 119991, Russia
| | - F Araoka
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa Wako, Saitama 351-0198, Japan
| | - H Nishikawa
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa Wako, Saitama 351-0198, Japan
| | - K Ishikawa
- Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
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Shvetsov SA, Rudyak VY, Gruzdenko AA, Emelyanenko AV. Axisymmetric skyrmion-like structures in spherical-cap droplets of chiral nematic liquid crystal. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Dubtsov AV, Pasechnik SV, Shmeliova DV, Saidgaziev AS, Gongadze E, Iglič A, Kralj S. Liquid crystalline droplets in aqueous environments: electrostatic effects. SOFT MATTER 2018; 14:9619-9630. [PMID: 30457151 DOI: 10.1039/c8sm01529e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We demonstrate the strong impact of electrostatic properties on radial-bipolar structural transitions in nematic liquid crystal (LC) droplets dispersed in different aqueous environments. In the experimental part of the study, we systematically changed the electrostatic properties of both LC droplets and aqueous solutions. Mixtures of nematics were studied by combining LC materials with negative (azoxybenzene compounds) and strongly positive (cyanobiphenyl) dielectric anisotropy. The aqueous solutions were manipulated by introducing either polyvinyl alcohol, glycerol, electrolyte or amphiphilic anionic surfactant SDS into water. In the supporting theoretical study, we identified the key parameters influencing the dielectric constant and the electric field strength of aqueous solutions. We also estimated the impact of different electrolytes on the Debye length at the LC-aqueous interface. The obtained results are further analysed for chemical and biological sensing applications.
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Affiliation(s)
- Alexander V Dubtsov
- Problem Laboratory of Molecular Acoustics, MIREA - Russian Technological University, 119454, 78 Vernadsky Avenue, Moscow, Russia.
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Photoinduced orientational structures of nematic liquid crystal droplets in contact with polyimide coated surface. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.01.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Shvetsov SA, Emelyanenko AV, Bugakov MA, Boiko NI, Liu JH. Photo-Orientation at the Interface between Thermotropic Nematic Liquid Crystal and Water Caused by Azobenzene Polymer Additives. POLYMER SCIENCE SERIES C 2018. [DOI: 10.1134/s1811238218010071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Shvetsov SA, Emelyanenko AV, Boiko NI, Zolot'ko AS, Zhang YS, Liu JH, Khokhlov AR. Optical orientation of nematic liquid crystal droplets via photoisomerization of an azodendrimer dopant. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2018; 9:870-879. [PMID: 29600148 PMCID: PMC5870153 DOI: 10.3762/bjnano.9.81] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/11/2018] [Indexed: 06/08/2023]
Abstract
Two sequential transformations of the orientational structure in nematic liquid crystal droplets containing a dendrimer additive (nanosized macromolecules with light-absorbing azobenzene terminal moieties) under light irradiation in the UV-blue spectral range were investigated. The origin of these transitions is in the change of the boundary conditions due to photoisomerization of the dendrimer adsorbed onto the liquid crystal-glycerol interface. It was shown that the photoisomerization processes of dendrimer molecules in a liquid crystal are accompanied by a spatial rearrangement of their azobenzene moieties, which is the key point in the explanation of the observed effects.
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Affiliation(s)
- Sergey A Shvetsov
- M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
- P.N. Lebedev Physical Institute, Moscow, 119991, Russia
| | | | - Natalia I Boiko
- M.V. Lomonosov Moscow State University, Moscow, 119991, Russia
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Rudyak VY, Krakhalev MN, Sutormin VS, Prishchepa OO, Zyryanov VY, Liu JH, Emelyanenko AV, Khokhlov AR. Electrically induced structure transition in nematic liquid crystal droplets with conical boundary conditions. Phys Rev E 2017; 96:052701. [PMID: 29347734 DOI: 10.1103/physreve.96.052701] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Indexed: 11/07/2022]
Abstract
Polymer-dispersed liquid crystal composites have been a focus of study for a long time for their unique electro-optical properties and manufacturing by "bottom-up" techniques at large scales. In this paper, nematic liquid crystal oblate droplets with conical boundary conditions (CBCs) under the action of electric field were studied by computer simulations and polarized optical microscopy. Droplets with CBCs were shown to prefer an axial-bipolar structure, which combines a pair of boojums and circular disclinations on a surface. In contrast to droplets with degenerate planar boundary conditions (PBCs), hybridization of the two structure types in droplets with CBCs leads to a two-minima energy profile, resulting in an abrupt structure transition and bistable behavior of the system. The nature of the low-energy barrier in droplets with CBCs makes it highly sensitive to external stimuli, such as electric or magnetic fields, temperature, and light. In particular, the value of the electric field of the structure reorientation in droplets with CBCs was found to be a few times smaller than the one for droplets with PBCs, and the droplet state remained stable after switching off the voltage.
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Affiliation(s)
- V Yu Rudyak
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
| | - M N Krakhalev
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia.,Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk 660041, Russia
| | - V S Sutormin
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia
| | - O O Prishchepa
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia.,Institute of Engineering Physics and Radio Electronics, Siberian Federal University, Krasnoyarsk 660041, Russia
| | - V Ya Zyryanov
- Kirensky Institute of Physics, Federal Research Center - Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk 660036, Russia
| | - J-H Liu
- Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - A V Emelyanenko
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
| | - A R Khokhlov
- Lomonosov Moscow State University, Faculty of Physics, Moscow 119991, Russia
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