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Yao J, Saielli G, Meng F, Wang Y. Phase coexistence in [C 22/C 1MIm] +[NO 3] - ionic-liquid mixtures and first-order phase transitions from homogeneous liquid to smectic B by varying the cation ratio. Phys Chem Chem Phys 2023; 25:21595-21603. [PMID: 37551110 DOI: 10.1039/d3cp01670f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
We perform molecular dynamics simulations to investigate the transition processes of [C22/C1MIm]+[NO3]- binary mixtures by varying the cation ratio of C22 to C1 at a fixed temperature of 400 K. The cation ratio is tuned by ranging C22 percentage from 0% to 100% with a fixed number of 4096 total simulated ion pairs. Our simulated-annealing results indicate that, at 400 K, pure C1 is a homogeneous liquid whilst pure C22 is an ionic liquid crystal (ILC) of smectic-B (SmB) type. With increasing C22 percentage, the system goes through a first-order phase transition from homogeneous liquid to nano-fragment liquid in the range from 15% to 17.5%, during which some of the individual cationic alkyl side chains locally aggregate to form small bundles "floating" in the polar "solvent" composed of anions and cationic head groups. Although the side chains in each bundle are parallelly aligned, the bundles distribute randomly without a global orientation. As the C22 percentage further increases, another first-order phase transition occurs to bring the system into the SmB ILC phase. Particularly, when the C22 percentage is in the range from 45% to 50%, the SmB phase coexists with the liquid phase containing both individual and bundled alkyl side chains.
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Affiliation(s)
- Jie Yao
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, P. O. Box 2735, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, China
| | - Giacomo Saielli
- CNR Institute on Membrane Technology, Unit of Padova, Via Marzolo, 1 - 35131, Padova, Italy
- Department of Chemical Sciences, University of Padova, Via Marzolo, 1 - 35131, Padova, Italy
| | - Fanlong Meng
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, P. O. Box 2735, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, China
- Center for Theoretical Interdisciplinary Sciences, Wenzhou Institute, University of Chinese Academy of Sciences, 1 Jinlian Road, Wenzhou, 325001, China
| | - Yanting Wang
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 55 East Zhongguancun Road, P. O. Box 2735, Beijing, 100190, China.
- School of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Beijing, 100049, China
- Center for Theoretical Interdisciplinary Sciences, Wenzhou Institute, University of Chinese Academy of Sciences, 1 Jinlian Road, Wenzhou, 325001, China
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Mazzilli V, Satoh K, Saielli G. Phase behaviour of mixtures of charged soft disks and spheres. SOFT MATTER 2023; 19:3311-3324. [PMID: 37093590 DOI: 10.1039/d3sm00223c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We have investigated the phase behaviour of mixtures of soft disks (Gay-Berne oblate ellipsoids, GB) and soft spheres (Lennard-Jones, LJ) with opposite charge as a model of ionic liquid crystals and colloidal suspensions. We have used constant volume Molecular Dynamics simulations and fixed the stoichiometry of the mixture in order to have electroneutrality; three systems have been selected GB : LJ = 1 : 2, GB : LJ = 1 : 1 and GB : LJ = 2 : 1. For each system we have selected three values of the scaled point charge q* of the GB particles, namely 0.5, 1.0 and 2.0 (and a corresponding negative scaled charge of the LJ particles that depends on the stoichiometric ratio). We have found a very rich mesomorphism with the formation, as a function of the scaled temperature, of the isotropic phase, the discotic nematic phase, the hexagonal columnar phase and crystal phases. While the structure of the high temperature phases was similar in all systems, the hexagonal columnar phases exhibited a highly variable morphology depending on the scaled charge and stoichiometry. On the one hand, GB : LJ = 1 : 2 systems form lamellar structures, akin to smectic phases, with an alternation of layers of disks (exhibiting an hexagonal columnar phase) and layers of LJ particles (in the isotropic phase). On the other hand, for the 2 : 1 stoichiometry we observe the formation of a frustrated hexagonal columnar phase with an alternating tilt direction of the molecular axis. We rationalize these findings based on the structure of the neutral ion pair dominating the behaviour at low temperature and high charge.
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Affiliation(s)
- Valerio Mazzilli
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
- CNR-ITM, Institute on Membrane Technology, Padova Unit, Via Marzolo, 1, 35131 Padova, Italy
| | - Katsuhiko Satoh
- Department of Chemistry, Osaka Sangyo University, Daito, Osaka, 574-8530, Japan.
| | - Giacomo Saielli
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
- CNR-ITM, Institute on Membrane Technology, Padova Unit, Via Marzolo, 1, 35131 Padova, Italy
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Haege C, Jagiella S, Giesselmann F. Towards Nematic Phases in Ionic Liquid Crystals - A Simulation Study. Chemphyschem 2023; 24:e202200424. [PMID: 36053025 PMCID: PMC10092135 DOI: 10.1002/cphc.202200424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 08/30/2022] [Indexed: 01/04/2023]
Abstract
Ionic liquid crystals (ILCs) are soft matter materials with broad liquid crystalline phases and intrinsic electric conductivity. They typically consist of a rod-shaped mesogenic ion and a smaller spherical counter-ion. Their mesomorphic properties can be easily tuned by exchanging the counter ion. ILCs show a strong tendency to form smectic A phases due to the segregation of ionic and the non-ionic molecular segments. Nematic phases are therefore extremely rare in ILCs and the question of why nematic phases are so exceptional in existing ILCs, and how nematic ILCs might be obtained in the future is of vital interest for both the fundamental understanding and the potential applications of ILCs. Here, we present the result of a simulation study, which highlights the crucial role of the location of the ionic charge on the rod-like mesogenic ions in the phase behaviour of ILCs. We find that shifting the charge from the ends towards the centre of the mesogenic ion destabilizes the liquid crystalline state and induces a change from smectic A to nematic phases.
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Affiliation(s)
- Christian Haege
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Stefan Jagiella
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Frank Giesselmann
- Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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Mazzilli V, Satoh K, Saielli G. Mixtures of discotic and spherical soft particles: de-mixing, liquid crystal behaviour and relative solubility. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Kapernaum N, Lange A, Ebert M, Grunwald MA, Haege C, Marino S, Zens A, Taubert A, Giesselmann F, Laschat S. Current Topics in Ionic Liquid Crystals. Chempluschem 2021; 87:e202100397. [PMID: 34931472 DOI: 10.1002/cplu.202100397] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/10/2021] [Indexed: 12/20/2022]
Abstract
Ionic liquid crystals (ILCs), that is, ionic liquids exhibiting mesomorphism, liquid crystalline phases, and anisotropic properties, have received intense attention in the past years. Among others, this is due to their special properties arising from the combination of properties stemming from ionic liquids and from liquid crystalline arrangements. Besides interesting fundamental aspects, ILCs have been claimed to have tremendous application potential that again arises from the combination of properties and architectures that are not accessible otherwise, or at least not accessible easily by other strategies. The current review highlights recent developments in ILC research, starting with some key fundamental aspects. Further subjects covered include the synthesis and variations of modern ILCs, including the specific tuning of their mesomorphic behavior. The review concludes with reflections on some applications that may be within reach for ILCs and finally highlights a few key challenges that must be overcome prior and during true commercialization of ILCs.
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Affiliation(s)
- Nadia Kapernaum
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Alyna Lange
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Golm, Germany
| | - Max Ebert
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Marco A Grunwald
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Christian Haege
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Sebastian Marino
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Anna Zens
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Andreas Taubert
- Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Golm, Germany
| | - Frank Giesselmann
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Sabine Laschat
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
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Peppel T, Köckerling M. New Low-Melting Triply Charged Homoleptic Cr(III)-Based Ionic Liquids in Comparison to Their Singly Charged Heteroleptic Analogues. MATERIALS (BASEL, SWITZERLAND) 2021; 14:2676. [PMID: 34065306 PMCID: PMC8160797 DOI: 10.3390/ma14102676] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/10/2021] [Accepted: 05/11/2021] [Indexed: 02/01/2023]
Abstract
A series of new low-melting triply charged homoleptic Cr(III)-based ionic liquids of the general formula (RMIm)3[Cr(NCS)6] (R = methyl, ethyl, n-butyl, benzyl) is reported. Their syntheses and properties are described in comparison to their singly charged heteroleptic analogues of the general formula (RMIm)[Cr(NCS)4L2] (R = methyl, ethyl, n-butyl, benzyl; L = pyridine, γ-picoline). In total, sixteen new Reineckate related salts with large imidazolium cations are described. Out of these, five compounds were crystallized, and their structures determined by single-crystal X-ray structure analyses. They all consisted of discrete anions and cations with octahedrally coordinated Cr(III) ions. In the structures, various hydrogen contacts interconnect the entities to build up hydrogen bonded networks. Thermal investigations showed relatively low melting points for the homoleptic complexes. The compounds with the [Cr(NCS)6]3- anion melt without decomposition and are stable up to 200 K above their melting points. The complex salts with the [Cr(NCS)4L2]- anion, in contrast, start to decompose and lose L molecules (Pyr or Pic) already at the melting point.
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Affiliation(s)
- Tim Peppel
- Leibniz-Institut für Katalyse e.V. (LIKAT), Heterogene Photokatalyse, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
| | - Martin Köckerling
- Institut für Chemie, Anorganische Festkörperchemie, Universität Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany;
- Department Life, Light and Matter, Universität Rostock, 18051 Rostock, Germany
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Bhowmik PK, Noori O, Chen SL, Han H, Fisch MR, Robb CM, Variyam A, Martinez-Felipe A. Ionic liquid crystals: Synthesis and characterization via NMR, DSC, POM, X-ray diffraction and ionic conductivity of asymmetric viologen bistriflimide salts. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.115370] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Liu M, Shiba H, Liu H, Peng H. Molecular-dynamics simulations on the mesophase transition induced by oscillatory shear in imidazolium-based ionic liquid crystals. Phys Chem Chem Phys 2021; 23:6496-6508. [PMID: 33688864 DOI: 10.1039/d0cp05677d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Molecular dynamics simulations were performed on a 1-dodecyl-3-methylimidazolium hexafluorophosphate ([C12mim][PF6]) ionic liquid crystal (ILC) with the application of an oscillatory shear. We found that the oscillatory shear can both accelerate and suppress mesophase formation depending on shear amplitude. A small amplitude shear can speed up the mesophase transition dynamics and result in a more ordered mesomorphic structure than that without shear, i.e., an effect of accelerated aging. The mesophase is destabilized when the shear amplitude is large enough, resulting in a smectic A (SmA) to liquid or a smectic B (SmB) to SmA transition, with the mesophase behaviour summarized in an out-of-equilibrium phase diagram. Inside the layer plane a medium-range hexatic order was observed, with the correlation length extending to several nanometres in the shear-induced SmA phase. We rationalize the nonequilibrium mesophase behaviour from the rheology of isotropic liquids, finding a temperature-independent critical relaxation time for the mesophase transition in the translational or rotational dynamics. This finding can be used to predict the mesophase behaviour in the sheared ILCs from the rheology of isotropic liquids.
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Affiliation(s)
- Min Liu
- School of Materials Science and Engineering, Central South University, Changsha 410083, China.
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Rzoska SJ, Starzonek S, Łoś J, Drozd-Rzoska A, Kralj S. Dynamics and Pretransitional Effects in C 60 Fullerene Nanoparticles and Liquid Crystalline Dodecylcyanobiphenyl (12CB) Hybrid System. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E2343. [PMID: 33255904 PMCID: PMC7761475 DOI: 10.3390/nano10122343] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/15/2020] [Accepted: 11/16/2020] [Indexed: 11/16/2022]
Abstract
The report shows the strong impact of fullerene C60 nanoparticles on phase transitions and complex dynamics of rod-like liquid crystal dodecylcyanobiphenyl (12CB), within the limit of small concentrations. Studies were carried out using broadband dielectric spectroscopy (BDS) via the analysis of temperature dependences of the dielectric constant, the maximum of the primary loss curve, and relaxation times. They revealed a strong impact of nanoparticles, leading to a ~20% change of dielectric constant even at x = 0.05% of C60 fullerene. The application of the derivative-based and distortion-sensitive analysis showed that pretransitional effects dominate in the isotropic liquid phase up to 65 K above the clearing temperature and in the whole Smectic A mesophase. The impact of nanoparticles on the pretransitional anomaly appearance is notable for the smectic-solid phase transition. The fragility-based analysis of relaxation times revealed the universal pattern of its temperature changes, associated with scaling via the "mixed" ("activated" and "critical") relation. Phase behavior and dynamics of tested systems are discussed within the extended Landau-de Gennes-Ginzburg mesoscopic approach.
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Affiliation(s)
- Sylwester J. Rzoska
- Institute of High Pressure Physics Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland; (S.S.); (J.Ł.); (A.D.-R.)
| | - Szymon Starzonek
- Institute of High Pressure Physics Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland; (S.S.); (J.Ł.); (A.D.-R.)
| | - Joanna Łoś
- Institute of High Pressure Physics Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland; (S.S.); (J.Ł.); (A.D.-R.)
| | - Aleksandra Drozd-Rzoska
- Institute of High Pressure Physics Polish Academy of Sciences, Sokołowska 29/37, 01-142 Warsaw, Poland; (S.S.); (J.Ł.); (A.D.-R.)
| | - Samo Kralj
- Laboratory of Physics of Complex Systems, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška 160, 2000 Maribor, Slovenia;
- Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
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Mann SK, Devgan MK, Franks WT, Huband S, Chan CL, Griffith J, Pugh D, Brooks NJ, Welton T, Pham TN, McQueen LL, Lewandowski JR, Brown SP. MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal. J Phys Chem B 2020; 124:4975-4988. [PMID: 32412761 PMCID: PMC7341529 DOI: 10.1021/acs.jpcb.0c02328] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structure and molecular order in the thermotropic ionic liquid crystal (ILC), [choline][geranate(H)octanoate], an analogue of Choline And GEranate (CAGE), which has potential for use as a broad-spectrum antimicrobial and transdermal and oral delivery agent, were investigated by magic-angle spinning (MAS) nuclear magnetic resonance (NMR), polarizing optical microscopy, small-angle X-ray scattering (SAXS), and mass spectrometry. Mass spectrometry and the 1H NMR chemical shift reveal that CAGE-oct is a dynamic system, with metathesis (the exchange of interacting ions) and hydrogen exchange occurring between hydrogen-bonded/ionic complexes such as [(choline)(geranate)(H)(octanoate)], [(choline)(octanoate)2(H)], and [(choline)(geranate)2(H)]. These clusters, which are shown by mass spectrometry to be significantly more stable than expected for typical electrostatic ion clusters, involve hydrogen bonding between the carboxylic acid, carboxylate, and hydroxyl groups, with rapid hydrogen bond breaking and re-formation observed to average the 1H chemical shifts. The formation of a partial bilayer liquid crystal (LC) phase was identified by SAXS and polarizing optical microscopy at temperatures below ∼293 K. The occurrence of this transition close to room temperature could be utilized as a potential temperature-induced "switch" of the anisotropic properties for particular applications. The presence of an isotropic component of approximately 23% was observed to coexist with the LC phase, as detected by polarizing optical microscopy and quantified by both 1H-13C dipolar-chemical shift correlation (DIPSHIFT) and 1H double-quantum (DQ) MAS NMR experiments. At temperatures above the LC-to-isotropic transition, intermediate-range order (clustering of polar and nonpolar domains), a feature of many ILs, persists. Site-specific order parameters for the LC phase of CAGE-oct were obtained from the MAS NMR measurement of the partially averaged 13C-1H dipolar couplings (DCH) by cross-polarization (CP) build-up curves and DIPSHIFT experiments, and 1H-1H dipolar couplings (DHH) by double-quantum (DQ) build-up curves. The corresponding order parameters, SCH and SHH, are in the range 0-0.2 and are lower compared to those for smectic (i.e., layered) phases of conventional nonionic liquid crystals, resembling those of lamellar phases formed by lyotropic surfactant-solvent systems.
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Affiliation(s)
- Sarah K Mann
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Mohit K Devgan
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - W Trent Franks
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.,Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Steven Huband
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
| | - Chi Long Chan
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Jeraime Griffith
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - David Pugh
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Nicholas J Brooks
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Tom Welton
- Department of Chemistry, Imperial College London, London SW7 2AZ, U.K
| | - Tran N Pham
- GSK R&D, Stevenage, Hertfordshire SG1 2NY, U.K
| | - Lisa L McQueen
- GSK R&D, Collegeville, Pennsylvania 19426, United States
| | | | - Steven P Brown
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
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