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Cao Y, Tan T, Walba DM, Clark NA, Ungar G, Zhu C, Zhang L, Liu F. Understanding and Manipulating Helical Nanofilaments in Binary Systems with Achiral Dopants. NANO LETTERS 2022; 22:4569-4575. [PMID: 35584547 DOI: 10.1021/acs.nanolett.2c01525] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Here, we report the relationship between helical pitch of the helical nanofilament (HNF) phase formed by bent-core molecule NOBOW and the concentration of achiral dopants 5CB and octane, using linearly polarized resonant soft X-ray scattering (RSoXS). Utilizing theory-based simulation, which fits well with the experiments, the molecular helices in the filament were probed and the superstructure of helical 5CB directed by groove of HNFs was observed. Quantitative pitch determination with RSoXS reveals that helical pitch variation is related to 5CB concentration with no temperature dependence. Doping rodlike immiscible 5CB led to a pitch shortening of up to 30%, which was attributed to a change in interfacial tension. By shedding light not only on phase behavior of binary systems but also enabling control over pitch length, our work may benefit various applications of HNF-containing binary systems, including optical rotation devices, circularly polarized light emitters, and chirality transfer agents.
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Affiliation(s)
- Yu Cao
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi'an Jiaotong University, Xi'an 710049, P.R. China
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, P.R. China
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Tianyi Tan
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi'an Jiaotong University, Xi'an 710049, P.R. China
| | - David M Walba
- Department of Chemistry and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - Noel A Clark
- Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, Colorado 80309, United States
| | - Goran Ungar
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi'an Jiaotong University, Xi'an 710049, P.R. China
| | - Chenhui Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Lei Zhang
- MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, School of Physics, Xi'an Jiaotong University, Xi'an 710049, P.R. China
| | - Feng Liu
- Shaanxi International Research Center for Soft Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi'an Jiaotong University, Xi'an 710049, P.R. China
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Molecular Simulation Approaches to the Study of Thermotropic and Lyotropic Liquid Crystals. CRYSTALS 2022. [DOI: 10.3390/cryst12050685] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Over the last decade, the availability of computer time, together with new algorithms capable of exploiting parallel computer architectures, has opened up many possibilities in molecularly modelling liquid crystalline systems. This perspective article points to recent progress in modelling both thermotropic and lyotropic systems. For thermotropic nematics, the advent of improved molecular force fields can provide predictions for nematic clearing temperatures within a 10 K range. Such studies also provide valuable insights into the structure of more complex phases, where molecular organisation may be challenging to probe experimentally. Developments in coarse-grained models for thermotropics are discussed in the context of understanding the complex interplay of molecular packing, microphase separation and local interactions, and in developing methods for the calculation of material properties for thermotropics. We discuss progress towards the calculation of elastic constants, rotational viscosity coefficients, flexoelectric coefficients and helical twisting powers. The article also covers developments in modelling micelles, conventional lyotropic phases, lyotropic phase diagrams, and chromonic liquid crystals. For the latter, atomistic simulations have been particularly productive in clarifying the nature of the self-assembled aggregates in dilute solution. The development of effective coarse-grained models for chromonics is discussed in detail, including models that have demonstrated the formation of the chromonic N and M phases.
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Yu G, Wilson MR. All-atom simulations of bent liquid crystal dimers: the twist-bend nematic phase and insights into conformational chirality. SOFT MATTER 2022; 18:3087-3096. [PMID: 35377382 DOI: 10.1039/d2sm00291d] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The liquid crystal dimer 1,7-bis-4-(4'-cyanobiphenyl)heptane (CB7CB) is known to exhibit a nematic-nematic phase transition, with the lower temperature phase identified as the twist-bend nematic (NTB) phase. Despite the achiral nature of the mesogen, the NTB phase demonstrates emergent chirality through the spontaneous formation of a helical structure. We present extensive molecular dynamics simulations of CB7CB using an all-atom force field. The NTB phase is observed in this model and, upon heating, shows phase transitions into the nematic (N) and isotropic phases. The simulated NTB phase returns a pitch of 8.35 nm and a conical tilt angle of 29°. Analysis of the bend angle between the mesogenic units reveals an average angle of 127°, which is invariant to the simulated phase. We have calculated distributions of the chirality order parameter, χ, for the ensemble of conformers in the NTB and N phases. These distributions elucidate that CB7CB is statistically achiral but can adopt chiral conformers with no preference for a specific handedness. Furthermore, there is no change in the extent of conformational chirality between the NTB and N phases. Using single-molecule stochastic dynamics simulations in the gas phase, we study the dimer series CBnCB (where n = 6, 7, 8 or 9) and CBX(CH2)5YCB (where X/Y = CH2, O or S) in terms of the bend angle and conformational chirality. We confirm that the bent molecular shape determines the ability of a dimer to exhibit the NTB phase rather than its potential to assume chiral conformers; as |χ|max increases with the spacer length, but the even-membered dimers have a linear shape in contrast to the bent nature of dimers with spacers of odd parity. For CBX(CH2)5YCB, it is found that |χ|max increases as the bend angle of the dimer decreases, while the flexibility of the dimers remains unchanged through the series.
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Affiliation(s)
- Gary Yu
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, UK.
| | - Mark Richard Wilson
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, UK.
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Czajkowski M, Feder-Kubis J, Potaniec B, Duda Ł, Cybińska J. On the Miscibility of Nematic Liquid Crystals with Ionic Liquids and Joint Reaction for High Helical Twisting Power Product(s). MATERIALS (BASEL, SWITZERLAND) 2021; 15:157. [PMID: 35009303 PMCID: PMC8745833 DOI: 10.3390/ma15010157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/18/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Abstract
Mixtures of nematic liquid crystals (LCs) with chiral ionic liquids (CILs) may find application as active materials for electrically driven broadband mirrors. Five nematic liquid crystal hosts were mixed with twenty three ionic liquids, including chiral ones, and studied in terms of their miscibility within the nematic phase. Phase diagrams of the mixtures with CILs which exhibited twisted nematic phase were determined. Miscibility, at levels between 2 and 5 wt%, was found in six mixtures with cyanobiphenyl-based liquid crystal host-E7. On the other hand, the highest changes in the isotropization temperature was found in the mixtures with isothiocyanate-based liquid crystal host-1825. Occurrence of chemical reactions was found. A novel chiral binaphtyl-based organic salt [N11116][BNDP] was synthesized and, in reaction to the 1825 host, resulted in high helical twisting power product(s). Selectivity of the reaction with the isothiocyanate-based liquid crystal was found.
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Affiliation(s)
- Maciej Czajkowski
- Advanced Materials Synthesis Research Group, Łukasiewicz Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, 54-066 Wroclaw, Poland; (B.P.); (Ł.D.); (J.C.)
| | - Joanna Feder-Kubis
- Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland;
| | - Bartłomiej Potaniec
- Advanced Materials Synthesis Research Group, Łukasiewicz Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, 54-066 Wroclaw, Poland; (B.P.); (Ł.D.); (J.C.)
| | - Łukasz Duda
- Advanced Materials Synthesis Research Group, Łukasiewicz Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, 54-066 Wroclaw, Poland; (B.P.); (Ł.D.); (J.C.)
- Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383 Wroclaw, Poland
| | - Joanna Cybińska
- Advanced Materials Synthesis Research Group, Łukasiewicz Research Network—PORT Polish Center for Technology Development, Stabłowicka 147, 54-066 Wroclaw, Poland; (B.P.); (Ł.D.); (J.C.)
- Faculty of Chemistry, University of Wroclaw, F. Joliot-Curie 14, 50-383 Wroclaw, Poland
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Kim BC, Walker M, Jo SY, Wilson MR, Takezoe H, Choi SW. Effect of terminal chain length on the helical twisting power in achiral bent-core molecules doped in a cholesteric liquid crystal. RSC Adv 2018; 8:1292-1295. [PMID: 35540888 PMCID: PMC9076949 DOI: 10.1039/c7ra11589j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 12/22/2017] [Indexed: 12/20/2022] Open
Abstract
We prepared a homologous series of achiral bent-core (BC) liquid crystals with different terminal alkoxy chain lengths, n (BC-n), and evaluated the helical twisting power (HTP) of the BC-n doped in a cholesteric liquid crystal. The BC-n molecules with longer terminal chains showed larger HTPs. To interpret this striking phenomenon, a stochastic dynamics simulation was performed to determine the distribution of the chirality order parameters (χ) for BC molecules with n = 8-16. The distribution of χ for each simulated conformation varied with n, and the variation tendency was different for molecules with n < 12 and n > 12 despite the linear relationship between HTP and n in the experiment.
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Affiliation(s)
- Byeong-Cheon Kim
- Department of Advanced Materials Engineering for Information and Electronics (BK21Plus), Kyung Hee University Yongin-shi Gyeonggi-do 17104 Korea
| | - Martin Walker
- Department of Chemistry, Durham University Lower Mountjoy, South Road DH13LE UK
| | - Seong-Yong Jo
- Department of Advanced Materials Engineering for Information and Electronics (BK21Plus), Kyung Hee University Yongin-shi Gyeonggi-do 17104 Korea
| | - Mark R Wilson
- Department of Chemistry, Durham University Lower Mountjoy, South Road DH13LE UK
| | - Hideo Takezoe
- Toyota Physical and Chemical Research Institute 41-1 Yokomichi Nagakute Aichi 480-1192 Japan
| | - Suk-Won Choi
- Department of Advanced Materials Engineering for Information and Electronics (BK21Plus), Kyung Hee University Yongin-shi Gyeonggi-do 17104 Korea
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