Local Structure and Flow Properties of Ionic Liquids on Charged and Inert Substrates

Jitvisate, Monchai; Seddon, James Richard Thorley

doi:10.1021/acs.jpcc.5b10727

Cited by 6 publications

(12 citation statements)

References 28 publications

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“…As the Coulombic interactions are not considered in the calculation of the surface parameters, this suggests a strong influence of the surface polarity on friction in the presence of a polar fluid (such as an ionic liquid), which is reflected by a substantial increase of the force corrugation. This is also consistent with experimental observations that point out the locking of counterions of IL on mica surfaces (charged surface) …”

Section: Discussionsupporting

confidence: 92%

“…This is also consistent with experimental observations that point out the locking of counterions of IL on mica surfaces (charged surface). 68 Over the past 20 years, a number of experimental and MD studies claimed the existence of a quasi-universal relationship between the slip length and the wetting properties of the liquid/solid couple, 69,70 although some recent studies have shown that the wetting properties alone can fail to predict the slip length. 71,72 For the present work, comparable wetting properties are expected for all of the carbon-based surfaces, and yet they display extremely different interfacial fiction coefficients (up to more than 2 orders of magnitude).…”

Section: ■ Discussionmentioning

confidence: 99%

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Orders of Magnitude Changes in the Friction of an Ionic Liquid on Carbonaceous Surfaces

et al. 2018

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The fast development of ionic liquids as new lubricants and carbon-based coatings as performant tribological surfaces calls for the characterization of their frictional and interfacial hydrodynamic behavior. Here we use molecular dynamics simulations to explore the response under shear of an ionic liquid confined between various carbon-based surfaces and an iron oxide surface for comparison. We show that extremely low fluid friction and giant hydrodynamic slippage can be obtained on graphite and to a lesser extent on diamond, but that friction on amorphous carbon surfaces is comparable to that on iron oxide. We relate these differences to the atom-scale roughness of the surfaces. In particular, although amorphous carbon surfaces are apolar, their nanometric roughness is enough to generate a fluid friction comparable to that of the extremely smooth but polar iron oxide surface. We also show that, at high shear rates, seemingly small differences in viscosity and interfacial friction can result in a significant change of the slip length. We finally discuss the consequences of the ultralow fluid friction that we observed on the macroscopic behavior of lubricated contacts.

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Section: Discussionsupporting

confidence: 92%

Section: ■ Discussionmentioning

confidence: 99%

Orders of Magnitude Changes in the Friction of an Ionic Liquid on Carbonaceous Surfaces

et al. 2018

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“…Previous experimental and theoretical studies on IL-water and IL-DMSO mixtures in front of uncharged and purely repulsive surfaces revealed some interesting insights and have underlined the entropic effects on the molecular structuring. [50,[52][53][54] However, due to strong electrostatic and dispersion interactions, it can be assumed that also enthalpic contributions play an important role. [55] Motivated by the above studies, here we propose a new qualitative measure of molecular interactions within IL bulk solutions.…”

Section: Introductionmentioning

confidence: 99%

“…[56] As representative IL solutions, we discuss IL-water and IL-DMSO solutions, which attracted some interest in the last years. [52,54] In view of these, the paper is organized as follows: we begin with an outline of the methodology in Section 2, discuss the results of our MD simulations in Section 3 and provide a summary on the relevance of these outcomes in Section 4.…”

Section: Introductionmentioning

confidence: 99%

Energetic Arguments on the Microstructural Analysis in Ionic Liquids

Kobayashi

Smiatek

Fyta

2021

Advcd Theory and Sims

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The interaction of ionic liquids (ILs) with additives or impurities is crucial for the performance of ILs in technological applications. In order to understand the interaction between these, an insight onto the microscopic arrangement of molecules is needed. As a representative case, 1-ethyl-3-methylimidazolium dicyanamide ([EMIM] + [DCA] − ) mixtures are studied with dimethyl sulfoxide (DMSO) and water in bulk phase using molecular dynamics (MD) simulations. Different molar fractions of DMSO and water are studied to elucidate the influence of the molecular solute concentration on the structuring of the ILs. The results indicate that DMSO-[EMIM] + [DCA] and water-[EMIM] + [DCA] − mixtures are defined by quite distinct molecular interactions between the species. By increasing the DMSO or water concentration, in the former the solute molecules are repelled from the ions, while in the latter they accumulate closer to the ions. The differences arise from the weakening of the interactions between the ions imposed by the presence of the water molecules whereas DMSO promotes a strengthening of these interactions. Accordingly, this study provides a deep understanding of the IL behavior in combination with neutral solute molecules and allows for a proper selection of IL-solute combinations in view of specific technological applications.

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“… 3 − 14 The intricate near-wall behavior of the ions then plays a governing role in interlayer slip, as well as in controlling accessibility to an underlying electrode for electron transfer. 2 , 15 − 17 …”

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confidence: 99%

Near-Wall Molecular Ordering of Dilute Ionic Liquids

Jitvisate

Seddon

2017

J. Phys. Chem. C

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The interfacial behavior of ionic liquids promises tunable lubrication as well as playing an integral role in ion diffusion for electron transfer. Diluting the ionic liquids optimizes bulk parameters, such as electric conductivity, and one would expect dilution to disrupt the near-wall molecular ordering. We study this ordering in the ionic liquids [Emim]+[NTf2]−, [Emim]+[DCA]−, and [C4mpyr]+[NTf2]−, diluted in the solvent dimethyl sulfoxide. We found a structural crossover from well-ordered ionic liquids to a well-ordered solvent with increasing dilution, but this occurs nonlinearly, with solvent molecules initially space-filling and solvating and later disrupting the ionic layers. This is of key importance for ionic liquids as optimized tunable nanolubricants.

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Local Structure and Flow Properties of Ionic Liquids on Charged and Inert Substrates

Cited by 6 publications

References 28 publications

Orders of Magnitude Changes in the Friction of an Ionic Liquid on Carbonaceous Surfaces

Orders of Magnitude Changes in the Friction of an Ionic Liquid on Carbonaceous Surfaces

Energetic Arguments on the Microstructural Analysis in Ionic Liquids

Near-Wall Molecular Ordering of Dilute Ionic Liquids

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