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Elstone N, Shimizu K, Shaw EV, Lane PD, D’Andrea L, Demé B, Mahmoudi N, Rogers SE, Youngs S, Costen ML, McKendrick KG, Canongia Lopes JN, Bruce DW, Slattery JM. Understanding the Liquid Structure in Mixtures of Ionic Liquids with Semiperfluoroalkyl or Alkyl Chains. J Phys Chem B 2023; 127:7394-7407. [PMID: 37555779 PMCID: PMC10461228 DOI: 10.1021/acs.jpcb.3c02647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/15/2023] [Indexed: 08/10/2023]
Abstract
By mixing ionic liquids (ILs), it is possible to fine-tune their bulk and interfacial structure. This alters their physical properties and solvation behavior and is a simple way to prepare a collection of ILs whose properties can be tuned to optimize a specific application. In this study, mixtures of perfluorinated and alkylated ILs have been prepared, and links between composition, properties, and nanostructure have been investigated. These different classes of ILs vary substantially in the flexibility and polarizability of their chains. Thus, a range of useful structural and physical property variations are accessible through mixing that will expand the library of IL mixtures available in an area that to this point has received relatively little attention. In the experiments presented herein, the physical properties and bulk structure of mixtures of 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide [C8MIM][Tf2N] and 1-(1H,1H,2H,2H-perfluorooctyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C8MIM-F13][Tf2N] have been prepared. The bulk liquid structure was investigated using a combination of small-angle X-ray and neutron scattering (SAXS and SANS, respectively) experiments in combination with atomistic molecular dynamics simulations and the measurement of density and viscosity. We observed that the addition of [C8MIM-F13][Tf2N] to [C8MIM][Tf2N] causes changes in the nanostructure of the IL mixtures that are dependent on composition so that variation in the characteristic short-range correlations is observed as a function of composition. Thus, while the length scales associated with the apolar regions (polar non-polar peak─PNPP) increase with the proportion of [C8MIM-F13][Tf2N] in the mixtures, perhaps surprisingly given the greater volume of the fluorocarbon chains, the length scale of the charge-ordering peak decreases. Interestingly, consideration of the contact peak shows that its origins are both in the direct anion···cation contact length scale and the nature (and hence volume) of the chains appended to the imidazolium cation.
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Affiliation(s)
- Naomi
S. Elstone
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
| | - Karina Shimizu
- Centro
de Química Estrutural, Institute of Molecular Sciences, Instituto
Superior Técnico, Universidade de
Lisboa, Av. Rovisco Pais, Lisboa 1049 001, Portugal
| | - Emily V. Shaw
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
| | - Paul D. Lane
- Institute
of Chemical Sciences, School of Engineering and Physical Sciences, Heriot−Watt University, Edinburgh EH14 4AS, U.K.
| | - Lucía D’Andrea
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
| | - Bruno Demé
- Institut
Laue−Langevin, Grenoble 38000, France
| | - Najet Mahmoudi
- ISIS
Neutron Source Facility, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Sarah E. Rogers
- ISIS
Neutron Source Facility, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Sarah Youngs
- ISIS
Neutron Source Facility, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K.
| | - Matthew L. Costen
- Institute
of Chemical Sciences, School of Engineering and Physical Sciences, Heriot−Watt University, Edinburgh EH14 4AS, U.K.
| | - Kenneth G. McKendrick
- Institute
of Chemical Sciences, School of Engineering and Physical Sciences, Heriot−Watt University, Edinburgh EH14 4AS, U.K.
| | - Jose N. Canongia Lopes
- Centro
de Química Estrutural, Institute of Molecular Sciences, Instituto
Superior Técnico, Universidade de
Lisboa, Av. Rovisco Pais, Lisboa 1049 001, Portugal
| | - Duncan W. Bruce
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
| | - John M. Slattery
- Department
of Chemistry, University of York, Heslington, York YO10
5DD, U.K.
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Ahmadi Khoshooei M, Maham Y. Enthalpic perspective on thermodynamic equilibrium of bulk and confined liquids: A review. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116411] [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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Tsuura M, Shuto A, Hiraki S, Imai Y, Sakamoto H, Matsubara H, Aratono M, Tanida H, Nitta K, Uruga T, Takiue T. Surface freezing and molecular miscibility of binary fluoroalkanol-alkanol liquid mixture. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.04.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Haji-Akbari A, Debenedetti PG. Thermodynamic and kinetic anisotropies in octane thin films. J Chem Phys 2015; 143:214501. [PMID: 26646882 DOI: 10.1063/1.4935801] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Confinement breaks the translational symmetry of materials, making all thermodynamic and kinetic quantities functions of position. Such symmetry breaking can be used to obtain configurations that are not otherwise accessible in the bulk. Here, we use computer simulations to explore the effect of substrate-liquid interactions on thermodynamic and kinetic anisotropies induced by a solid substrate. We consider n-octane nano-films that are in contact with substrates with varying degrees of attraction, parameterized by an interaction parameter ϵS. Complete freezing of octane nano-films is observed at low temperatures, irrespective of ϵS, while at intermediate temperatures, a frozen monolayer emerges at solid-liquid and vapor-liquid interfaces. By carefully inspecting the profiles of translational and orientational relaxation times, we confirm that the translational and orientational degrees of freedom are decoupled at these frozen monolayers. At sufficiently high temperatures, however, free interfaces and solid-liquid interfaces close to loose (low-ϵS) substrates undergo "pre-freezing," characterized by mild peaks in several thermodynamic quantities. Two distinct dynamic regimes are observed at solid-liquid interfaces. The dynamics is accelerated in the vicinity of loose substrates, while sticky (high-ϵS) substrates decelerate dynamics, sometimes by as much as two orders of magnitude. These two distinct dynamical regimes have been previously reported by Haji-Akbari and Debenedetti [J. Chem. Phys. 141, 024506 (2014)] for a model atomic glass-forming liquid. We also confirm the existence of two correlations-proposed in the above-mentioned work-in solid-liquid subsurface regions of octane thin films, i.e., a correlation between atomic density and normal stress, and between atomic translational relaxation time and lateral stress. Finally, we inspect the ability of different regions of an octane film to explore the potential energy landscape by performing inherent structure calculations, and observe no noticeable difference between the free surface and the bulk in efficiently exploring the potential energy landscape. This is unlike the films of model atomic glass formers that tend to sample their respective landscape more efficiently at free surfaces. We discuss the implications of this finding to the ability of octane-and other n-alkanes-to form ultrastable glasses.
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Affiliation(s)
- Amir Haji-Akbari
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Pablo G Debenedetti
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
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Mitani K, Imai Y, Ina T, Nitta K, Tanida H, Uruga T, Matsubara H, Aratono M, Takiue T. Effect of Hydrophobic Chain Structure on Phase Transition and Domain Formation of Hybrid Alcohol Films Adsorbed at the Hexane/Water Interface. J Phys Chem B 2015; 119:12436-45. [PMID: 26308905 DOI: 10.1021/acs.jpcb.5b07632] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The phase transition and domain formation of the adsorbed film of two kinds of hybrid alcohols (CF3(CF2)m-1(CH2)nOH, FmHnOH), 2-perfluorooctylethanol (F8H2OH) and 2-perfluorohexylhexanol (F6H6OH), as a mixture at the hexane/water interface was investigated by interfacial tensiometry and X-ray reflection. The interfacial tension γ versus total molality m curve of pure F8H2OH has a break point at high concentration, and thus, the mean area per molecule A changes discontinuously at high interfacial pressure π, corresponding to the phase transition between expanded and condensed films. The Fresnel divided reflectivity R/RF versus Qz plots in the expanded state was well-fitted by the domain model for incoherent interference to determine the interfacial coverage, which is the fraction of the interface covered by the condensed phase. This indicates that the expanded film is heterogeneous and consists of a condensed F8H2OH domain, the size of which is larger than the X-ray coherence length (∼5 μm). In the mixed system, the discontinuous change in A at the phase transition point becomes small with increasing the bulk composition of F6H6OH X2 in the mixture, and eventually the A value changes continuously; i.e, the phase transition becomes obscure in X2 ≥ 0.6. This behavior was linked to an increase in interfacial coverage with X2. Furthermore, the R/RF versus Qz plot was fitted by the domain model for coherent interference, suggesting that the size of the domain is smaller than 5 μm. These results are probably due to the reduction of domain line tension by preferential adsorption of F6H6OH at the F8H2OH domain boundary.
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Affiliation(s)
- Kenta Mitani
- Department of Chemistry, Faculty of Sciences, Kyushu University , Fukuoka 812-8581, Japan
| | - Yosuke Imai
- Faculty of Arts and Science, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Toshiaki Ina
- Japan Synchrotron Radiation Research Institute , Hyogo 678-5198, Japan
| | - Kiyofumi Nitta
- Japan Synchrotron Radiation Research Institute , Hyogo 678-5198, Japan
| | - Hajime Tanida
- Japan Synchrotron Radiation Research Institute , Hyogo 678-5198, Japan
| | - Tomoya Uruga
- Japan Synchrotron Radiation Research Institute , Hyogo 678-5198, Japan
| | - Hiroki Matsubara
- Department of Chemistry, Faculty of Sciences, Kyushu University , Fukuoka 812-8581, Japan
| | - Makoto Aratono
- Department of Chemistry, Faculty of Sciences, Kyushu University , Fukuoka 812-8581, Japan
| | - Takanori Takiue
- Department of Chemistry, Faculty of Sciences, Kyushu University , Fukuoka 812-8581, Japan.,Faculty of Arts and Science, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
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