1
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Stanković I, Dašić M, Jovanović M, Martini A. Effects of Water Content on the Transport and Thermodynamic Properties of Phosphonium Ionic Liquids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:9049-9058. [PMID: 38641549 DOI: 10.1021/acs.langmuir.4c00372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/21/2024]
Abstract
We present a numerical investigation of the influence of water content on the dynamic properties of a family of phosphonium-based room-temperature ionic liquids. The study presents a compelling correlation between structural changes in water-ionic liquid solutions and thermodynamic and transport properties across diverse systems. The results for phosphonium ionic liquids are compared with 1-butyl-3-methylimidazolium hexaphosphate ([bmim]PF6) as a reference. Through this approach, phosphonium cation structure-related characteristics can be identified and placed within the broader context of ionic liquids. These insights are underpinned by observed changes in interaction energy, boiling point, diffusion rate, and viscosity, highlighting the crucial role of water molecules in weakening the strength of interactions between ions within the ionic liquid. The investigation also explains temperature-dependent trends in phosphonium cations, showing that alkyl group length and molecular symmetry are important tuning parameters for the strength of Coulomb interactions. These results contribute to a refined understanding of phosphonium ionic liquid behavior in the presence of water, offering valuable insights for optimizing their use in diverse fields.
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Affiliation(s)
- Igor Stanković
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, Belgrade 11080, Serbia
| | - Miljan Dašić
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, Belgrade 11080, Serbia
| | - Mateja Jovanović
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, Belgrade 11080, Serbia
| | - Ashlie Martini
- Department of Mechanical Engineering, University of California, Merced, California 95343, United States
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2
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Nuthalapati K, Sheng YJ, Tsao HK. Atypical wetting behavior of binary mixtures of partial and total wetting liquids: leak-out phenomena. Colloids Surf A Physicochem Eng Asp 2023. [DOI: 10.1016/j.colsurfa.2023.131299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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3
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Taßler S, Bonatout N, Eusébio TM, Valente RM, Rego T, Ibrahim H, Morgado P, J. M. Filipe E, Goldmann M, Fontaine P. Surface behaviour of 1-alkyl-3-methylimidazolium ionic liquids at the air-water-interface. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.121028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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4
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Huang HJ, Nuthalapati K, Sheng YJ, Tsao HK. Precursor Film of Self-propelled Droplets: Inducing Motion of a Static Droplet. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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5
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Shiomoto S, Higuchi H, Yamaguchi K, Takaba H, Kobayashi M. Spreading Dynamics of a Precursor Film of Ionic Liquid or Water on a Micropatterned Polyelectrolyte Brush Surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:3049-3056. [PMID: 33667098 DOI: 10.1021/acs.langmuir.0c03260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Time evolution of the microscopic wetting velocity of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI) or water on a micrometer-scale line-patterned surface with a poly(3-sulfopropyl methacrylate) brush and a hydrophobic perfluoroalkyl monolayer was precisely measured by direct observation using optical microscopy and a selective dyeing method over a long period (178 days). When a liquid droplet was placed on the dyed line-patterned brush surface, the liquid penetrated and spread into the polymer brush layer, forming a precursor thin film that extended beyond the macroscopic contact line. The elongation proceeded in two stages by an adiabatic process followed by a diffusive process. The elongation distance X increased with time in proportion to t2.6 for water and t0.81 for EMI-TFSI during the adiabatic process. In a diffusive process, the advancing velocity of the precursor film was markedly reduced to be expressed as X ∝ t0.66 for water and X ∝ t0.21 for EMI-TFSI, indicating that the diffusive process was affected by the energy dissipation of the wetting system. The high viscosity and the strong molecular interaction of EMI-TFSI with the polymer brush gave a large entropy change during the wetting process to result in a slower spreading velocity.
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Affiliation(s)
- Shohei Shiomoto
- Graduate School of Engineering, Kogakuin University, Tokyo 192-0015, Japan
| | - Hayato Higuchi
- Graduate School of Engineering, Kogakuin University, Tokyo 192-0015, Japan
| | - Kazuo Yamaguchi
- School of Advanced Engineering, Kogakuin University, Tokyo 192-0015, Japan
| | - Hiromitsu Takaba
- School of Advanced Engineering, Kogakuin University, Tokyo 192-0015, Japan
| | - Motoyasu Kobayashi
- School of Advanced Engineering, Kogakuin University, Tokyo 192-0015, Japan
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6
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Ivanova N, Esenbaev T. Wetting and dewetting behaviour of hygroscopic liquids: Recent advancements. Curr Opin Colloid Interface Sci 2021. [DOI: 10.1016/j.cocis.2020.101399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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7
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Lu Y, Chen W, Wang Y, Huo F, Dong Y, Wei L, He H. Research Progress on the Preparation and Properties of Two Dimensional Structure of Ionic Liquids. ACTA CHIMICA SINICA 2021. [DOI: 10.6023/a20100475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Campos RM, Alves ACPM, Lima MAL, Farinha AFM, Cardoso JPS, Mendes A, Costa JCS, Santos LMNBF. Morphology, Structure, and Dynamics of Pentacene Thin Films and Their Nanocomposites with [C
2
C
1
im][NTf
2
] and [C
2
C
1
im][OTF] Ionic Liquids. Chemphyschem 2020; 21:1814-1825. [DOI: 10.1002/cphc.202000431] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/18/2020] [Indexed: 11/09/2022]
Affiliation(s)
- Ricardo M. Campos
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Alexandre C. P. M. Alves
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Marco A. L. Lima
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Artur F. M. Farinha
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - João P. S. Cardoso
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Adélio Mendes
- LEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy Faculdade de Engenharia Universidade do Porto Portugal
| | - José C. S. Costa
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
- LEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy Faculdade de Engenharia Universidade do Porto Portugal
| | - Luís M. N. B. F. Santos
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
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9
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Wang YL, Li B, Sarman S, Mocci F, Lu ZY, Yuan J, Laaksonen A, Fayer MD. Microstructural and Dynamical Heterogeneities in Ionic Liquids. Chem Rev 2020; 120:5798-5877. [PMID: 32292036 PMCID: PMC7349628 DOI: 10.1021/acs.chemrev.9b00693] [Citation(s) in RCA: 197] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/11/2022]
Abstract
Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.
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Affiliation(s)
- Yong-Lei Wang
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Bin Li
- School
of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, P. R. China
| | - Sten Sarman
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Francesca Mocci
- Department
of Chemical and Geological Sciences, University
of Cagliari, I-09042 Monserrato, Italy
| | - Zhong-Yuan Lu
- State
Key Laboratory of Supramolecular Structure and Materials, Institute
of Theoretical Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Jiayin Yuan
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- State
Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
- Centre of
Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania
- Department
of Engineering Sciences and Mathematics, Division of Energy Science, Luleå University of Technology, SE-97187 Luleå, Sweden
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
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10
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An R, Qiu X, Shah FU, Riehemann K, Fuchs H. Controlling the nanoscale friction by layered ionic liquid films. Phys Chem Chem Phys 2020; 22:14941-14952. [PMID: 32588010 DOI: 10.1039/d0cp02146f] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nanofriction coefficient of ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), on the surfaces of mica and graphite was investigated using atomic force microscopy (AFM). A pronounced layered spatial distribution was found in the IL film formed on the solid substrates and can be divided into 3 well distinguishable regions exhibiting different physical properties with increasing distance from the substrate. We found that the friction coefficient (μ) increases monotonically as the layering thickness decreases, no matter what the thickness of the bulk IL is. This suggests that the layering assembled IL at solid surfaces is more important than the bulk phase in determining the magnitude of the nanoscale friction. The increase in the friction coefficient as the layering thickness decreases is most likely attributed to the assembled ordered IL layers closer to the substrate surfaces having a greater activation barrier for unlocking the surfaces to allow shear.
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Affiliation(s)
- Rong An
- Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China. and Center for Nanotechnology (CeNTech), Institute of Physics, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Xiuhua Qiu
- Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China.
| | - Faiz Ullah Shah
- Chemistry of Interfaces, Luleå University of Technology, SE 971 87 Luleå, Sweden
| | - Kristina Riehemann
- Center for Nanotechnology (CeNTech), Institute of Physics, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Harald Fuchs
- Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China. and Center for Nanotechnology (CeNTech), Institute of Physics, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
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11
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Wang Y, Li L. Uncovering the Underlying Mechanisms Governing the Solidlike Layering of Ionic Liquids (ILs) on Mica. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:2743-2756. [PMID: 32101445 DOI: 10.1021/acs.langmuir.9b03865] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Significant progress has been made in understanding the IL-solid interface in the past three decades, and a key finding is that ILs can form solidlike layers at the interface. It has been recognized that the electrostatic forces at the solid-IL interface and self-assembly of ILs are key enablers of the IL layering. However, regarding the layering structure of ILs, research from different laboratories is not consistent; i.e., the number of solidlike layers could range from 0 to ∼60, indicating the complexity of the underlying mechanisms and/or the existence of overlooked key parameters. In the current review, we will discuss the underlying mechanisms and key parameters governing the layering of ILs on mica, the most studied model solid. First, we will present the experimental findings from various laboratories, both consistent and contradictory ones, and summarize the current understanding of the governing mechanisms. Then, we will discuss the possible key parameters, including the structure of ILs, surface modification and contamination of mica, and cosolvent impacting the solidlike layering of ILs. Finally, we will discuss future research directions in uncovering the underlying mechanisms.
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Affiliation(s)
- Yali Wang
- Department of Chemistry and Chemical Engineering, Yulin University, Yulin, Shaanxi, P.R. China 719000
- Department of Chemical & Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Lei Li
- Department of Chemical & Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
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12
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Kiratidis AL, Miklavcic SJ. Density functional theory of confined ionic liquids: A survey of the effects of ion type, molecular charge distribution, and surface adsorption. J Chem Phys 2019; 150:184502. [DOI: 10.1063/1.5093552] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Adrian L. Kiratidis
- Phenomics and Bioinformatics Research Centre, School of Information Technology and Mathematical Sciences, University of South Australia, Mawson Lakes, SA, Australia
| | - Stanley J. Miklavcic
- Phenomics and Bioinformatics Research Centre, School of Information Technology and Mathematical Sciences, University of South Australia, Mawson Lakes, SA, Australia
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13
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Dašić M, Stanković I, Gkagkas K. Molecular dynamics investigation of the influence of the shape of the cation on the structure and lubrication properties of ionic liquids. Phys Chem Chem Phys 2019; 21:4375-4386. [DOI: 10.1039/c8cp07364c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A theoretical study of the influence of the geometry of the cation on the response of ionic liquids to confinement and mechanical strain is presented. The specific friction is low and the friction force decreases with tail size. The low hysteretic losses during the linear cyclic motion suggest strong slip inside the gap.
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Affiliation(s)
- Miljan Dašić
- Scientific Computing Laboratory
- Center for the Study of Complex Systems
- Institute of Physics Belgrade
- University of Belgrade
- 11080 Belgrade
| | - Igor Stanković
- Scientific Computing Laboratory
- Center for the Study of Complex Systems
- Institute of Physics Belgrade
- University of Belgrade
- 11080 Belgrade
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14
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Gong X, Wang B, Li L. Spreading of Nanodroplets of Ionic Liquids on the Mica Surface. ACS OMEGA 2018; 3:16398-16402. [PMID: 31458275 PMCID: PMC6643696 DOI: 10.1021/acsomega.8b02423] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 11/22/2018] [Indexed: 06/01/2023]
Abstract
Previously, the molecular structure of ionic liquids (ILs) next to a solid surface has been extensively studied because the IL-solid interfaces are critical to many important applications. What is largely unknown is the mobility of ILs confined to a solid surface. The solid-like stable structure of ILs on the solid surfaces has been reported in previous research, which indicates that the mobility of ILs next to a solid surface is quite low and the structure of ILs will not change with time. However, here, we show that the nanodroplets of ILs flow on the mica surface, which suggest that, at a small scale, the solid-like stable structure of ILs on the solid surfaces indeed changes with time. Interestingly, although the IL nanodroplets show a layered structure, no terrace-like flow of the droplet has been observed, which has been attributed to the weak mica-IL interaction at low humidity.
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Affiliation(s)
- Xiao Gong
- State
Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China
- Department
of Chemical & Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Bingchen Wang
- Department
of Chemical & Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Lei Li
- Department
of Chemical & Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
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15
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Dašić M, Stanković I, Gkagkas K. Influence of confinement on flow and lubrication properties of a salt model ionic liquid investigated with molecular dynamics. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:130. [PMID: 30377867 DOI: 10.1140/epje/i2018-11740-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 10/09/2018] [Indexed: 06/08/2023]
Abstract
We present a molecular dynamics study of the effects of confinement on the lubrication and flow properties of ionic liquids. We use a coarse-grained salt model description of ionic liquid as a lubricant confined between finite solid plates and subjected to two dynamic regimes: shear and cyclic loading. The impact of confinement on the ion arrangement and mechanical response of the system has been studied in detail and compared to static and bulk properties. The results have revealed that the wall slip has a profound influence on the force built-up as a response to mechanical deformation and that at the same time in the dynamic regime interaction with the walls represents a principal driving force governing the behaviour of ionic liquid in the gap. We also observe a transition from a dense liquid to an ordered and potentially solidified state of the ionic liquid taking place under variable normal loads and under shear.
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Affiliation(s)
- Miljan Dašić
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080, Belgrade, Serbia.
| | - Igor Stanković
- Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080, Belgrade, Serbia
| | - Konstantinos Gkagkas
- Advanced Technology Division, Toyota Motor Europe NV/SA, Technical Center, Hoge Wei 33B, 1930, Zaventem, Belgium
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16
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Gong X, Wang B, Kozbial A, Li L. From Molecular Arrangement to Macroscopic Wetting of Ionic Liquids on the Mica Surface: Effect of Humidity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:12167-12173. [PMID: 30230344 DOI: 10.1021/acs.langmuir.8b02450] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
To optimize the wetting performance of ionic liquids (ILs) on solid surfaces, which is important in catalysis, lubrication, and energy storage, it is critical to control the molecular arrangement of ILs at the IL/solid interface. Here, we report our experimental results, showing that tuning humidity is a facile and effective approach manipulating the molecular arrangement and thus controlling the macroscopic wettability of ILs on the mica surface. Fourier transform infrared spectroscopy, contact angle testing, and atomic force microscopy results showed that with the increase of humidity, more water adsorbs on the mica surface, which dissolves and mobilizes K+ on the mica. As a result, the cations of ILs occupy the empty spot left by the K+ and initiate the layering of ILs. The water-enabled ion exchange and IL layering processes result in not only the decrease of the IL contact angle on the mica but also the time-dependent contact angle. The finding here potentially provides a new dimension tailoring the performance of ILs at the IL/solid interface.
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Affiliation(s)
- Xiao Gong
- State Key Laboratory of Silicate Materials for Architectures , Wuhan University of Technology , Wuhan 430070 , China
- Department of Chemical & Petroleum Engineering, Swanson School of Engineering , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , United States
| | - Bingchen Wang
- Department of Chemical & Petroleum Engineering, Swanson School of Engineering , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , United States
| | - Andrew Kozbial
- Department of Chemical & Petroleum Engineering, Swanson School of Engineering , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , United States
| | - Lei Li
- Department of Chemical & Petroleum Engineering, Swanson School of Engineering , University of Pittsburgh , Pittsburgh , Pennsylvania 15261 , United States
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17
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David A, Fajardo OY, Kornyshev AA, Urbakh M, Bresme F. Electrotunable lubricity with ionic liquids: the influence of nanoscale roughness. Faraday Discuss 2017; 199:279-297. [DOI: 10.1039/c6fd00244g] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The properties of ionic liquids can be modified by applying an external electrostatic potential, providing a route to control their performance in nanolubrication applications. Most computational studies to date have focused on the investigation of smooth surfaces. Real surfaces are generally inhomogeneous and feature roughness of different length scales. We report here a study of the possible effects that surface roughness may have on electrotunable lubricity with ionic liquids, performed here by means of non-equilibrium molecular dynamics simulations. In order to advance our understanding of the interplay of friction and substrate structure we investigate coarse grained models of ionic liquids confined in model surfaces with nanometer roughness. The friction is shown to depend on the roughness of the substrate and the direction of shear. For the investigated systems, the friction coefficient is found to increase with roughness. These results are in contrast with previous studies, where roughness induced reduction of friction was reported, and they highlight the strong sensitivity of the friction process to the structure of the surfaces. The friction force features a maximum at a specific surface charge density. This behaviour is reminiscent of the one reported in ionic liquids confined by flat surfaces, showing the generality of this physical effect in confined ionic liquids. We find that an increase of the substrate–liquid dispersion interactions shifts the maximum to lower surface charges. This effect opens a route to control electrotunable friction phenomena by tuning both the electrostatic potential and the composition of the confining surfaces.
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Affiliation(s)
- Alessio David
- Department of Chemistry
- Imperial College London
- SW7 2AZ London
- UK
- Department of Physics
| | - Oscar Y. Fajardo
- Department of Chemistry
- Imperial College London
- SW7 2AZ London
- UK
- Department of Chemistry
| | | | - Michael Urbakh
- Department of Chemistry
- Tel Aviv University
- 69978 Tel Aviv
- Israel
| | - Fernando Bresme
- Department of Chemistry
- Imperial College London
- SW7 2AZ London
- UK
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18
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Abstract
The role of relative humidity (RH) on the wetting behavior of droplets of two [Rmim][NTf2] ionic liquids (ILs) on a mica surface was investigated and water vapor adsorption was found to enhance the ILs precursor film formation and droplet spreading.
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Affiliation(s)
- Zhantao Wang
- Key Laboratory of Optoelectronic Devices and Systems of MOE
- Institute of Optoelectronics
- Shenzhen University
- Shenzhen 518060
- China
| | - Fuxi Shi
- College of Mechanical and Electronic Engineering
- Northwest A&F University
- Yangling 712100
- China
| | - Cunlu Zhao
- Key Laboratory of Thermo-Fluid Science and Engineering of MOE
- School of Energy and Power Engineering
- Xi'an Jiaotong University
- Xi'an 710049
- China
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19
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Wang Z, Li H, Atkin R, Priest C. Influence of Water on the Interfacial Nanostructure and Wetting of [Rmim][NTf2] Ionic Liquids at Mica Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:8818-8825. [PMID: 27486675 DOI: 10.1021/acs.langmuir.6b01790] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The effect of water concentration on the interfacial nanostructure and wetting behavior of a family of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Rmim][NTf2], at the surface of mica was investigated by contact angle measurement and atomic force microscopy (AFM). AFM reveals that interfacial layers of ILs observed at the surface of mica for "dry" ILs are not present for water-saturated ILs. The interaction of the IL ions of [Rmim][NTf2] with water molecules through hydrogen bonding is suspected to disrupt IL ion layering and precursor film growth on mica. Without the IL precursor film, contact angle relaxation of "wet" ILs on mica is less significant and ambient vapor adsorption becomes more important in determining the macroscopic wetting behavior.
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Affiliation(s)
- Zhantao Wang
- Ian Wark Research Institute, University of South Australia , Mawson Lakes 5095, Australia
| | - Hua Li
- Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle , Callaghan, New South Wales 2308, Australia
| | - Rob Atkin
- Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle , Callaghan, New South Wales 2308, Australia
| | - Craig Priest
- Ian Wark Research Institute, University of South Australia , Mawson Lakes 5095, Australia
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Costa JCS, Mendes A, Santos LMNBF. Morphology of Imidazolium-Based Ionic Liquids as Deposited by Vapor Deposition: Micro-/Nanodroplets and Thin Films. Chemphyschem 2016; 17:2123-7. [DOI: 10.1002/cphc.201600198] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Indexed: 11/10/2022]
Affiliation(s)
- José C. S. Costa
- Centro de Investigação em Química (CIQ); Departamento de Química e Bioquímica; Faculdade de Ciências; Universidade do Porto; Rua do Campo Alegre, 687 4169-007 Porto Portugal
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE); Faculdade de Engenharia; Universidade do Porto; Rua Dr. Roberto Frias 4200-465 Porto Portugal
| | - Adélio Mendes
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE); Faculdade de Engenharia; Universidade do Porto; Rua Dr. Roberto Frias 4200-465 Porto Portugal
| | - Luís M. N. B. F. Santos
- Centro de Investigação em Química (CIQ); Departamento de Química e Bioquímica; Faculdade de Ciências; Universidade do Porto; Rua do Campo Alegre, 687 4169-007 Porto Portugal
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21
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Fajardo OY, Bresme F, Kornyshev AA, Urbakh M. Electrotunable Friction with Ionic Liquid Lubricants: How Important Is the Molecular Structure of the Ions? J Phys Chem Lett 2015; 6:3998-4004. [PMID: 26722768 DOI: 10.1021/acs.jpclett.5b01802] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Using nonequilibrium molecular dynamics simulations and a coarse-grained model of ionic liquids, we have investigated the impact that the shape and the intramolecular charge distribution of the ions have on the electrotunable friction with ionic liquid nanoscale films. We show that the electric field induces significant structural changes in the film, leading to dramatic modifications of the friction force. Comparison of the present work with previous studies using different models of ionic liquids indicate that the phenomenology presented here applies to a wide range of ionic liquids. In particular, the electric-field-induced shift of the slippage plane from the solid-liquid interface to the interior of the film and the nonmonotonic variation of the friction force are common features of ionic lubricants under strong confinement. We also demonstrate that the molecular structure of the ions plays an important role in determining the electrostriction and electroswelling of the confined film, hence showing the importance of ion-specific effects in electrotunable friction.
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Affiliation(s)
- O Y Fajardo
- School of Chemistry, Tel Aviv University , 69978 Tel Aviv, Israel
| | - Fernando Bresme
- Deparment of Chemistry, Imperial College London , SW7 2AZ London, United Kingdom
| | - Alexei A Kornyshev
- Deparment of Chemistry, Imperial College London , SW7 2AZ London, United Kingdom
| | - Michael Urbakh
- School of Chemistry, Tel Aviv University , 69978 Tel Aviv, Israel
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22
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Capozza R, Vanossi A, Benassi A, Tosatti E. Squeezout phenomena and boundary layer formation of a model ionic liquid under confinement and charging. J Chem Phys 2015; 142:064707. [PMID: 25681935 DOI: 10.1063/1.4907747] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Electrical charging of parallel plates confining a model ionic liquid down to nanoscale distances yields a variety of charge-induced changes in the structural features of the confined film. That includes even-odd switching of the structural layering and charging-induced solidification and melting, with important changes of local ordering between and within layers, and of squeezout behavior. By means of molecular dynamics simulations, we explore this variety of phenomena in the simplest charged Lennard-Jones coarse-grained model including or excluding the effect a neutral tail giving an anisotropic shape to one of the model ions. Using these models and open conditions permitting the flow of ions in and out of the interplate gap, we simulate the liquid squeezout to obtain the distance dependent structure and forces between the plates during their adiabatic approach under load. Simulations at fixed applied force illustrate an effective electrical pumping of the ionic liquid, from a thick nearly solid film that withstands the interplate pressure for high plate charge to complete squeezout following melting near zero charge. Effective enthalpy curves obtained by integration of interplate forces versus distance show the local minima that correspond to layering and predict the switching between one minimum and another under squeezing and charging.
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Affiliation(s)
- R Capozza
- International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
| | - A Vanossi
- International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
| | - A Benassi
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - E Tosatti
- International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
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23
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Delcheva I, Ralston J, Beattie DA, Krasowska M. Static and dynamic wetting behaviour of ionic liquids. Adv Colloid Interface Sci 2015; 222:162-71. [PMID: 25103860 DOI: 10.1016/j.cis.2014.07.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/08/2014] [Accepted: 07/08/2014] [Indexed: 11/29/2022]
Abstract
Ionic liquids (ILs) are a unique family of molecular liquids ('molten salts') that consist of a combination of bulky organic cations coupled to inorganic or organic anions. The net result of steric hindrance and strong hydrogen bonding between components results in a material that is liquid at room temperature. One can alter the properties of ionic liquids through chemical modification of anion and cation, thus tailoring the IL for a given application. One such property that can be controlled or selected is the wettability of an IL on a particular solid substrate. However, the study of wetting of ionic liquids is complicated by the care required for accurate and reproducible measurement, due to both the susceptibility of the IL properties to water content, as well as to the sensitivity of wettability measurements to the state of the solid surface. This review deals with wetting studies of ILs to date, including both static and dynamic wetting, as well as issues concerning line tension and the formation of precursor and wetting films.
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Affiliation(s)
- Iliana Delcheva
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Adelaide, Australia
| | - John Ralston
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Adelaide, Australia
| | - David A Beattie
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Adelaide, Australia
| | - Marta Krasowska
- Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Adelaide, Australia.
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24
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Gong X, Kozbial A, Li L. What causes extended layering of ionic liquids on the mica surface? Chem Sci 2015; 6:3478-3482. [PMID: 28706709 PMCID: PMC5492871 DOI: 10.1039/c5sc00832h] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 04/19/2015] [Indexed: 01/08/2023] Open
Abstract
Extended layering of ionic liquids (ILs) on the mica surface has been reported by several groups previously and it is generally accepted that the electrostatic interaction at the IL/mica interface is critical to the observed extended layering. Here we report that, indeed, water adsorption on the mica surface is the key to the extended layering of ionic liquids. The atomic force microscopy (AFM), attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR) and contact angle (CA) results show that ionic liquids form extended layering on a mica surface under ambient conditions when water is adsorbed on the mica surface under such conditions. However, when airborne hydrocarbon contaminants replace the water on the mica surface at the elevated temperatures, instead of layering, ionic liquids exhibit droplet structure, i.e., dewetting. Based on the experimental results, we propose that water enables ion exchange between K+ and the cations of ILs on the mica surface and thus triggers the ordered packing of cations/anions in ILs, resulting in extended layering.
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Affiliation(s)
- Xiao Gong
- Department of Chemical & Petroleum Engineering , Swanson School of Engineering , University of Pittsburgh , Pittsburgh , PA 15261 , USA
| | - Andrew Kozbial
- Department of Chemical & Petroleum Engineering , Swanson School of Engineering , University of Pittsburgh , Pittsburgh , PA 15261 , USA
| | - Lei Li
- Department of Chemical & Petroleum Engineering , Swanson School of Engineering , University of Pittsburgh , Pittsburgh , PA 15261 , USA
- Department of Mechanical Engineering & Materials Science , Swanson School of Engineering , University of Pittsburgh , Pittsburgh , PA 15261 , USA .
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25
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Affiliation(s)
- Robert Hayes
- Discipline
of Chemistry, The University of Newcastle, NSW 2308, Callaghan, Australia
| | - Gregory G. Warr
- School
of Chemistry, The University of Sydney, NSW 2006, Sydney, Australia
| | - Rob Atkin
- Discipline
of Chemistry, The University of Newcastle, NSW 2308, Callaghan, Australia
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26
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Beattie DA, Harmer-Bassell SL, Ho TTM, Krasowska M, Ralston J, Sellapperumage PMF, Wąsik P. Spectroscopic study of ionic liquid adsorption from solution onto gold. Phys Chem Chem Phys 2015; 17:4199-209. [DOI: 10.1039/c4cp05558f] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
HMIM NTf2 adsorbs on gold from ethanol to form a patchy bilayer. ‘Bound’ anion (filled anion) and ‘bound’ cation (filled blue) sit underneath a layer of cation (empty blue) and anion (empty orange). The IL regions are separated by oxidised gold (darker colour).
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Affiliation(s)
- David A. Beattie
- The Ian Wark Research Institute
- University of South Australia
- Adelaide
- Australia
| | | | - Tracey T. M. Ho
- The Ian Wark Research Institute
- University of South Australia
- Adelaide
- Australia
| | - Marta Krasowska
- The Ian Wark Research Institute
- University of South Australia
- Adelaide
- Australia
| | - John Ralston
- The Ian Wark Research Institute
- University of South Australia
- Adelaide
- Australia
| | | | - Patryk Wąsik
- The Ian Wark Research Institute
- University of South Australia
- Adelaide
- Australia
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