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Zheng X, Bourg IC. Nanoscale Prediction of the Thermal, Mechanical, and Transport Properties of Hydrated Clay on 10 6- and 10 15-Fold Larger Length and Time Scales. ACS NANO 2023; 17:19211-19223. [PMID: 37774155 PMCID: PMC10569101 DOI: 10.1021/acsnano.3c05751] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 09/25/2023] [Indexed: 10/01/2023]
Abstract
Coupled thermal, hydraulic, mechanical, and chemical (THMC) processes, such as desiccation-driven cracking or chemically driven fluid flow, significantly impact the performance of composite materials formed by fluid-mediated nanoparticle assembly, including energy storage materials, ordinary Portland cement, bioinorganic nanocomposites, liquid crystals, and engineered clay barriers used in the isolation of hazardous wastes. These couplings are particularly important in the isolation of high-level radioactive waste (HLRW), where heat generated by radioactive decay can drive the temperature up to at least 373 K in the engineered barrier. Here, we use large-scale all-atom molecular dynamics simulations of hydrated smectite clay nanoparticle assemblages to predict the fundamental THMC properties of hydrated compacted clay over a wide range of temperatures (up to 373 K) and dry densities relevant to HLRW management. Equilibrium simulations of clay-water mixtures at different hydration levels are analyzed to quantify material properties, including thermal conductivity, heat capacity, thermal expansion, suction, water and ion self-diffusivity, and hydraulic conductivity. Predictions are validated against experimental results for the properties of compacted bentonite clay. Our results demonstrate the feasibility of using atomistic-level simulations of assemblages of clay nanoparticles on scales of tens of nanometers and nanoseconds to infer the properties of compacted bentonite on scales of centimeters and days, a direct upscaling over 6 orders of magnitude in space and 15 orders of magnitude in time.
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Affiliation(s)
- Xiaojin Zheng
- Department
of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Ian C. Bourg
- Department
of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
- High
Meadows Environmental Institute, Princeton
University, Princeton, New Jersey 08544, United States
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2
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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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3
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Wachsmann SB, Bauhof J, Raab AR, Zens A, Sottmann T, Laschat S. N-Alkylimidazolium carboxylates as a new type of catanionic surface active ionic liquid: synthesis, thermotropic behavior and micellization in water. SOFT MATTER 2022; 18:7773-7781. [PMID: 36177986 DOI: 10.1039/d2sm00854h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Aiming at a new type of salt-free CASAIL (Catanionic Surface Active IL) for electrochemical applications or emulsifiers, dispersants, and foaming or antifoaming agents, we combined mesogenic anions (carboxylate) and cations (imidazolium) of similar shape and size to synthesize a series of congruent ion pairs of 1-alkyl-3-methylimidazolium alkylcarboxylates [Cnmim][Cm-1COO] (n = 10-16, m = 10-16). With particular focus on alkyl chain length varieties in both, imidazolium cations and carboxylate anions (n/m), the self-assembly in the bulk phase and in solution was investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), X-ray diffraction (XRD) experiments and surface tension measurements. Our results revealed that the presence of long alkyl chains on both the cation n and anion m leads to improved thermal stability of the bulk material while maintaining broad lamellar (SmA) mesophases. In water, we observed a strong and linear decrease of log(cmc) for increasing both the carboxylate anion and imidazolium cation chain length due to the increasing hydrophobic effect. Surprisingly, for both thermotropic behavior and micellization, the chain length of the carboxylate anion had a stronger impact than the chain length of the imidazolium cation, indicating its greater surface activity and tendency to form micelles.
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Affiliation(s)
- Sebastian B Wachsmann
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
| | - Jessica Bauhof
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
| | - Aileen Rebecca Raab
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
| | - Anna Zens
- Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.
| | - Thomas Sottmann
- 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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Majhi D, Dai J, Dvinskikh SV. Insights into cation-anion hydrogen bonding in mesogenic ionic liquids: an NMR study. Phys Chem Chem Phys 2022; 24:23532-23539. [PMID: 36129074 DOI: 10.1039/d2cp03188d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The hydrogen-bonding interaction is studied in imidazolium-based mesogenic ionic liquids in their isotropic, smectic, and solid phases and in a nanoconfined state by proton solid-state nuclear magnetic resonance (NMR). In the smectic phase, the more basic anions form stronger hydrogen bonds. A small decrease of H-bonding in the mesophase with respect to that in the isotropic phase is associated with the presence of a layered assembly with high orientational order and limited conformational freedom. Hydrogen bond strength is not sensitive to the cation structural modification as long as the aprotic nature of the material is preserved. The strong cation-anion hydrogen bonding observed in the smectic phases provides direct support for the presence of ionic sublayers which form in ionic liquid crystals regardless of the location and alignment of the charged group in the cation, particularly irrespective of whether the charged group occupies a terminal or central position in the cation structure. A comparison of the results obtained in isotropic, liquid-crystalline, and solid states shows that in the bulk materials the dynamic state of ions ranging from high reorientational and translational freedom to partial orientation and positional order to full immobilization, respectively, has no strong impact on the cation-anion hydrogen bond strength. On the other hand, nanoconfinement of ionic liquid crystals led to hydrogen bond disruption due to competing interactions of anions with a solid interface.
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Affiliation(s)
- Debashis Majhi
- KTH Royal Institute of Technology, Stockholm, Sweden. .,Stockholm University, Stockholm, Sweden
| | - Jing Dai
- KTH Royal Institute of Technology, Stockholm, Sweden.
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Wettstein A, Diddens D, Heuer A. Controlling Li + transport in ionic liquid electrolytes through salt content and anion asymmetry: a mechanistic understanding gained from molecular dynamics simulations. Phys Chem Chem Phys 2022; 24:6072-6086. [PMID: 35212346 DOI: 10.1039/d1cp04830a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In this work, we report the results from molecular dynamics simulations of lithium salt-ionic liquid electrolytes (ILEs) based either on the symmetric bis[(trifluoromethyl)sulfonyl]imide (TFSI-) anion or its asymmetric analogue 2,2,2-(trifluoromethyl)sulfonyl-N-cyanoamide (TFSAM-). Relating lithium's coordination environment to anion mean residence times and diffusion constants confirms the remarkable transport behaviour of the TFSAM--based ILEs that has been observed in recent experiments: for increased salt doping, the lithium ions must compete for the more attractive cyano over oxygen coordination and a fragmented landscape of solvation geometries emerges, in which lithium appears to be less strongly bound. We present a novel, yet statistically straightforward methodology to quantify the extent to which lithium and its solvation shell are dynamically coupled. By means of a Lithium Coupling Factor (LCF) we demonstrate that the shell anions do not constitute a stable lithium vehicle, which suggests for this electrolyte material the commonly termed "vehicular" lithium transport mechanism could be more aptly pictured as a correlated, flow-like motion of lithium and its neighbourhood. Our analysis elucidates two separate causes why lithium and shell dynamics progressively decouple with higher salt content: on the one hand, an increased sharing of anions between lithium limits the achievable LCF of individual lithium-anion pairs. On the other hand, weaker binding configurations naturally entail a lower dynamic stability of the lithium-anion complex, which is particularly relevant for the TFSAM--containing ILEs.
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Affiliation(s)
- Alina Wettstein
- Institut für physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, D-48149 Münster, Germany.
| | - Diddo Diddens
- Institut für Energie- und Klimaforschung, Ionics in Energy Storage, Helmholtz Institut Münster, Forschungszentrum Jülich, Corrensstraße 46, 48149 Münster, Germany
| | - Andreas Heuer
- Institut für physikalische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 28/30, D-48149 Münster, Germany. .,Institut für Energie- und Klimaforschung, Ionics in Energy Storage, Helmholtz Institut Münster, Forschungszentrum Jülich, Corrensstraße 46, 48149 Münster, Germany
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Ishino K, Shingai H, Hikita Y, Yoshikawa I, Houjou H, Iwase K. Cold Crystallization and the Molecular Structure of Imidazolium-Based Ionic Liquid Crystals with a p-Nitroazobenzene Moiety. ACS OMEGA 2021; 6:32869-32878. [PMID: 34901637 PMCID: PMC8655916 DOI: 10.1021/acsomega.1c04866] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 11/10/2021] [Indexed: 06/14/2023]
Abstract
The cold crystallization mechanism of 1-{[4'-(4″-nitrophenylazo)phenyloxy]}hexyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate ionic liquid crystal was investigated based on thermal analysis, structural analysis, infrared spectroscopy, and quantum chemical calculations. By conducting thorough structural characterization, we found that the prerequisite for cold crystallization is the irreversible molecular conformational alteration induced by the initial heating of the as-grown crystal into a smectic liquid crystal. The originally linear cation molecule bends and forms a step-stair conformation that persists throughout the subsequent heating and cooling processes as phase transition occurs from the crystal phase to the liquid crystal phase and then to the isotropic liquid phase. The formation of cold crystal occurs because of the choice of molecular stability over crystalline stability. Given the exothermic anomaly exhibited upon heating generic crystals to cold crystals, these findings demonstrate the promising potential of this ionic liquid crystal for thermal energy storage applications.
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Affiliation(s)
- Katsuma Ishino
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
| | - Hajime Shingai
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
| | - Yasuyuki Hikita
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
| | - Isao Yoshikawa
- Institute
of Industrial Science, The University of
Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Hirohiko Houjou
- Institute
of Industrial Science, The University of
Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
- Environmental
Science Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Katsunori Iwase
- DENSO
CORPORATION, 500-1 Minamiyama, Komenoki-cho, Nisshin, Aichi 470-0111, Japan
- Institute
of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-Ku, Nagoya, Aichi 464-8601, Japan
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