1
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Onuki A. Ions and dipoles in electric field: nonlinear polarization and field-dependent chemical reaction. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2024; 47:3. [PMID: 38206545 DOI: 10.1140/epje/s10189-023-00398-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 12/17/2023] [Indexed: 01/12/2024]
Abstract
We investigate electric-field effects in dilute electrolytes with nonlinear polarization. As a first example of such systems, we add a dipolar component with a relatively large dipole moment [Formula: see text] to an aqueous electrolyte. As a second example, the solvent itself exhibits nonlinear polarization near charged objects. For such systems, we present a Ginzburg-Landau free energy and introduce field-dependent chemical potentials, entropy density, and stress tensor, which satisfy general thermodynamic relations. In the first example, the dipoles accumulate in high-field regions, as predicted by Abrashikin et al.[Phys.Rev.Lett. 99, 077801 (2007)]. Finally, we consider the case, where Bjerrum ion pairs form a dipolar component with nonlinear polarization. The Bjerrum dipoles accumulate in high-field regions, while field-induced dissociation was predicted by Onsager [J. Chem. Phys.2, 599 (1934)]. We present an expression for the field-dependent association constant K(E), which depends on the field strength nonmonotonically.
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Affiliation(s)
- Akira Onuki
- Department of Physics, Kyoto University, Kyoto, 606-8502, Japan.
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2
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Sprik M. Continuum model of the simple dielectric fluid: consistency between density based and continuum mechanics methods. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1887950] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- M. Sprik
- Department of Chemistry, University of Cambridge, Cambridge, UK
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3
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Zemb T, Rosenberg R, Marčelja S, Haffke D, Dufrêche JF, Kunz W, Horinek D, Cölfen H. Phase separation of binary mixtures induced by soft centrifugal fields. Phys Chem Chem Phys 2021; 23:8261-8272. [PMID: 33527947 DOI: 10.1039/d0cp01527j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We use the model system ethanol-dodecane to demonstrate that giant critical fluctuations induced by easily accessible weak centrifugal fields as low as 2000g can be observed above the miscibility gap of a binary liquid mixture. Moreover, several degrees above the phase transition, i.e. in the one-phase region, strong gradients of ethanol concentration occur upon centrifugation. In this case, the standard interpretation of sedimentation equilibrium in the analytical ultracentrifuge (AUC) yields an apparent molar mass of ethanol three orders of magnitude higher than the real value. Notably, these composition gradients have no influence on the distribution gradient of solutes such as dyes like Nile red. The thick opaque interphase formed upon centrifugation does not appear as the commonly observed sharp meniscus, but as a turbidity zone, similar to critical opalescence. This layer is a few millimeters thick and separates two fluids with low compositional gradients. All these effects can be qualitatively understood and explained using the Flory-Huggins solution model coupled to classical density functional theory (DFT). In this domain hetero-phase fluctuations can be triggered by gravity even far from the critical point. Taking into account Jean Perrin's approach to external fields in colloids, a self-consistent definition of the Flory effective volume and an explicit calculation of the total free energy per unit volume is possible.
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Affiliation(s)
- Thomas Zemb
- Institute for Separation Chemistry ICSM U Montpellier/CEA/CNRS/ENSCM, Marcoule, France
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4
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Jung D, Harting J, Sega M. Monolayer Structures of Supramolecular Antagonistic Salt Aggregates. J Phys Chem B 2021; 125:2351-2359. [PMID: 33634691 DOI: 10.1021/acs.jpcb.0c10005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The speculated presence of monomolecular lamellae of antagonistic salts in oil-water mixtures has left several open questions besides their hypothetical existence, including their microscopic structure and stabilization mechanism. Here, we simulate the spontaneous formation of supramolecular aggregates of the antagonistic salt sodium tetraphenylborate (NaBPh4) in water and 3-methylpyridine (3-MP) at the atomistic level. We show that, indeed, the lamellae are formed by a monomolecular layer of the anion, enveloped by 3-MP and hydrated sodium counterions. To understand which thermodynamic forces drive the aggregation, we compare the full-atomistic model with a simplified one for the salt and show that the strong hydrophobic effect granted by the large excluded volume of the anion, together with electrostatic repulsion, suffice to explain the stability of the monomolecular lamellae.
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Affiliation(s)
- David Jung
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy, Forschungszentrum Jülich, Fürther Straße 248, 90429 Nürnberg, Germany
| | - Jens Harting
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy, Forschungszentrum Jülich, Fürther Straße 248, 90429 Nürnberg, Germany
| | - Marcello Sega
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy, Forschungszentrum Jülich, Fürther Straße 248, 90429 Nürnberg, Germany
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5
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Mußotter M, Bier M, Dietrich S. Heterogeneous surface charge confining an electrolyte solution. J Chem Phys 2020; 152:234703. [PMID: 32571064 DOI: 10.1063/5.0006208] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The structure of dilute electrolyte solutions close to a surface carrying a spatially inhomogeneous surface charge distribution is investigated by means of classical density functional theory within the approach of fundamental measure theory. For electrolyte solutions, the influence of these inhomogeneities is particularly strong because the corresponding characteristic length scale is the Debye length, which is large compared to molecular sizes. Here, a fully three-dimensional investigation is performed, which accounts explicitly for the solvent particles, and thus provides insight into effects caused by ion-solvent coupling. The present study introduces a versatile framework to analyze a broad range of types of surface charge heterogeneities even beyond the linear response regime. This reveals a sensitive dependence of the number density profiles of the fluid components and of the electrostatic potential on the magnitude of the charge as well as on the details of the surface charge patterns at small scales.
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Affiliation(s)
- Maximilian Mußotter
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany
| | - Markus Bier
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany
| | - S Dietrich
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany
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6
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Glende G, de Wijn AS, Pousaneh F. The Vanishing water/oil interface in the presence of antagonistic salt. J Chem Phys 2020; 152:124707. [DOI: 10.1063/1.5142811] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Gudrun Glende
- Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | - Astrid S. de Wijn
- Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
- Department of Physics, Stockholm University, Stockholm, Sweden
| | - Faezeh Pousaneh
- Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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7
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Zhang C, Sprik M. Electromechanics of the liquid water vapour interface. Phys Chem Chem Phys 2020; 22:10676-10686. [PMID: 32025669 DOI: 10.1039/c9cp06901a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Two collective properties distinguishing the thin liquid water vapour interface from the bulk liquid are the anisotropy of the pressure tensor giving rise to surface tension and the orientational alignment of the molecules leading to a finite dipolar surface potential. Both properties can be regarded as capillary phenomena and are likely to be coupled. We have investigated this coupling by determining the response of the tangential component of the surface tension to the application of an electric field normal to the surface using finite field molecular dynamics simulations. We find an upside down parabola with a maximum shifted away from zero field. Comparing the molecular dynamics results to a phenomenological electromechanical model we relate the zero field derivative of the tangential part of the surface tension to the electrostatic potential generated by the spontaneous interface polarization. When interpreted with this model our simulations also indicate that Kelvin forces due to electric field gradients at a polarized interface play an important role in the effective dielectric response.
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Affiliation(s)
- Chao Zhang
- Department of Chemistry-Ångström Laboratory, Uppsala University, Lägerhyddsvägen 1, Box 538, 75121, Uppsala, Sweden
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8
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Effect of potassium thiocyanate on the phase diagram of Methyl Ethyl Ketone + secondary Butyl Alcohol + Water: Search for the Quadruple Critical Point. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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9
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Jung D, Rivas N, Harting J. How antagonistic salts cause nematic ordering and behave like diblock copolymers. J Chem Phys 2019; 150:064912. [PMID: 30769987 DOI: 10.1063/1.5085660] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present simulation results and an explanatory theory on how antagonistic salts affect the spinodal decomposition of binary fluid mixtures. We find that spinodal decomposition is arrested and complex structures form only when electrostatic ion-ion interactions are small. In this case, the fluid and ion concentrations couple and the charge field can be approximated as a polynomial function of the relative fluid concentrations alone. When the solvation energy associated with transferring an ion from one fluid phase to the other is of the order of a few kBT, the coupled fluid and charge fields evolve according to the Ohta-Kawasaki free energy functional. This allows us to accurately predict structure sizes and reduce the parameter space to two dimensionless numbers. The lamellar structures induced by the presence of the antagonistic salt in our simulations exhibit a high degree of nematic ordering and the growth of ordered domains over time follows a power law. This power law carries a time exponent proportional to the salt concentration. We qualitatively reproduce and interpret neutron scattering data from previous experiments of similar systems. The dissolution of structures at high salt concentrations observed in these experiments agrees with our simulations, and we explain it as the result of a vanishing surface tension due to electrostatic contributions. We conclude by presenting 3D results showing the same morphologies as predicted by the Ohta-Kawasaki model as a function of volume fraction and suggesting that our findings from 2D systems remain valid in 3D.
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Affiliation(s)
- David Jung
- Forschungszentrum Jülich, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Fürther Straße 248, 90429 Nürnberg, Germany
| | - Nicolas Rivas
- Forschungszentrum Jülich, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Fürther Straße 248, 90429 Nürnberg, Germany
| | - Jens Harting
- Forschungszentrum Jülich, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Fürther Straße 248, 90429 Nürnberg, Germany
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10
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Bore SL, Kolli HB, Kawakatsu T, Milano G, Cascella M. Mesoscale Electrostatics Driving Particle Dynamics in Nonhomogeneous Dielectrics. J Chem Theory Comput 2019; 15:2033-2041. [DOI: 10.1021/acs.jctc.8b01201] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sigbjørn Løland Bore
- Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, PO Box 1033 Blindern, 0315 Oslo, Norway
| | - Hima Bindu Kolli
- Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, PO Box 1033 Blindern, 0315 Oslo, Norway
| | - Toshihiro Kawakatsu
- Department of Physics, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Miyagi, Japan
| | - Giuseppe Milano
- Department of Organic Materials Science, Yamagata University, 4-3-16 Jonan ,Yonezawa, Yamagata-ken 992-8510, Japan
| | - Michele Cascella
- Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, PO Box 1033 Blindern, 0315 Oslo, Norway
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11
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Mußotter M, Bier M, Dietrich S. Electrolyte solutions at heterogeneously charged substrates. SOFT MATTER 2018; 14:4126-4140. [PMID: 29693687 DOI: 10.1039/c8sm00497h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The influence of a chemically or electrically heterogeneous distribution of interaction sites at a planar substrate on the number density of an adjacent fluid is studied by means of classical density functional theory (DFT). In the case of electrolyte solutions the effect of this heterogeneity is particularly long ranged, because the corresponding relevant length scale is set by the Debye length which is large compared to molecular sizes. The DFT used here takes the solvent particles explicitly into account and thus captures phenomena, inter alia, due to ion-solvent coupling. The present approach provides closed analytic expressions describing the influence of chemically and electrically nonuniform walls. The analysis of isolated δ-like interactions, isolated interaction patches, and hexagonal periodic distributions of interaction sites reveals a sensitive dependence of the fluid density profiles on the type of the interaction, as well as on the size and the lateral distribution of the interaction sites.
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Affiliation(s)
- Maximilian Mußotter
- Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany.
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12
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Sadakane K, Fujii K, Tsuzuki S, Watanabe H, Umebayashi Y. Solvation state of sodium tetraphenylborate in 3-methylpyridine and its aqueous solutions. J Mol Liq 2017. [DOI: 10.1016/j.molliq.2017.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Bier M, Mars J, Li H, Mezger M. Salt-induced microheterogeneities in binary liquid mixtures. Phys Rev E 2017; 96:022603. [PMID: 28950527 DOI: 10.1103/physreve.96.022603] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Indexed: 11/07/2022]
Abstract
The salt-induced microheterogeneity (MH) formation in binary liquid mixtures is studied by small-angle x-ray scattering (SAXS) and liquid state theory. Previous experiments have shown that this phenomenon occurs for antagonistic salts, whose cations and anions prefer different components of the solvent mixture. However, so far the precise mechanism leading to the characteristic length scale of MHs has remained unclear. Here, it is shown that MHs can be generated by the competition of short-ranged interactions and long-ranged monopole-dipole interactions. The experimental SAXS patterns can be reproduced quantitatively by fitting to the derived correlation functions without assuming any specific model. The dependency of the MH structure with respect to ionic strength and temperature is analyzed. Close to the demixing phase transition, critical-like behavior occurs with respect to the spinodal line in the phase diagram.
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Affiliation(s)
- Markus Bier
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany.,Institute for Theoretical Physics IV, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
| | - Julian Mars
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.,Institute of Physics and MAINZ Graduate School, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Hailong Li
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Markus Mezger
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.,Institute of Physics and MAINZ Graduate School, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
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14
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Katsir Y, Tsori Y. Recent advances in liquid mixtures in electric fields. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:063002. [PMID: 27991433 DOI: 10.1088/1361-648x/29/6/063002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
When immiscible liquids are subject to electric fields interfacial forces arise due to a difference in the permittivity or the conductance of the liquids, and these forces lead to shape change in droplets or to interfacial instabilities. In this topical review we discuss recent advances in the theory and experiments of liquids in electric fields with an emphasis on liquids which are initially miscible and demix under the influence of an external field. In purely dielectric liquids demixing occurs if the electrode geometry leads to sufficiently large field gradients. In polar liquids field gradients are prevalent due to screening by dissociated ions irrespective of the electrode geometry. We examine the conditions for these 'electro prewetting' transitions and highlight few possible systems where they might be important, such as in stabilization of colloids and in gating of pores in membranes.
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Affiliation(s)
- Yael Katsir
- Department of Chemical Engineering and the Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel
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15
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Pousaneh F, Edholm O, Maciołek A. Molecular dynamics simulation of a binary mixture near the lower critical point. J Chem Phys 2017; 145:014501. [PMID: 27394111 DOI: 10.1063/1.4954768] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
2,6-lutidine molecules mix with water at high and low temperatures but in a wide intermediate temperature range a 2,6-lutidine/water mixture exhibits a miscibility gap. We constructed and validated an atomistic model for 2,6-lutidine and performed molecular dynamics simulations of 2,6-lutidine/water mixture at different temperatures. We determined the part of demixing curve with the lower critical point. The lower critical point extracted from our data is located close to the experimental one. The estimates for critical exponents obtained from our simulations are in a good agreement with the values corresponding to the 3D Ising universality class.
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Affiliation(s)
- Faezeh Pousaneh
- Theoretical Biological Physics, Department of Theoretical Physics, Royal Institute of Technology (KTH), AlbaNova University Center, SE-106 91 Stockholm, Sweden
| | - Olle Edholm
- Theoretical Biological Physics, Department of Theoretical Physics, Royal Institute of Technology (KTH), AlbaNova University Center, SE-106 91 Stockholm, Sweden
| | - Anna Maciołek
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
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16
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Prevost S, Lopian T, Pleines M, Diat O, Zemb T. Small-angle scattering and morphologies of ultra-flexible microemulsions. J Appl Crystallogr 2016; 49:2063-2072. [PMID: 27980512 PMCID: PMC5139994 DOI: 10.1107/s1600576716016150] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 10/11/2016] [Indexed: 11/23/2022] Open
Abstract
Three-component fluids can exhibit structured density fluctuations, and their small-angle scattering patterns present similarities to those of classical microemulsions. One general analytical expression with two additive contributions (one for the two immiscible fluids and a smaller one for a structured fluid) allows the whole phase diagram to be mapped in the single-phase domain. The phase diagrams of ternary mixtures of partly miscible solvents containing a hydrotropic co-solvent exhibit a variable miscibility gap and one critical point. This work investigates the entire monophasic region far from and near to the miscibility gap in octan-1-ol/ethanol/water, for which ultra-flexible microemulsions (UFMEs) are observed by small-angle scattering techniques. SWAXS (combined small- and wide-angle X-ray scattering) allows the elucidation of these types of structure. Three distinct areas can be identified in the phase diagram, with scattering data resembling those from direct, bicontinuous and reverse local structures. These UFMEs are far more polydisperse than their surfactant-based counterparts. Water-rich and solvent-rich domains are only delimited by a small excess of hydrotrope, instead of a well defined surfactant layer of fixed area per molecule. It is shown that all scattering spectra obtained for the nanostructured compositions can be modelled by a simple unified analytical model composed of two uncorrelated contributions. The main one is the Ornstein–Zernike formula for composition fluctuations which gives information about the pseudo-phase domain size. The second is a Lorentzian that captures the structure of at least one of the coexisting pseudo-phases. No Porod law can be measured in the SAXS domain. The proposed expression gives access to two characteristic sizes as well as one inter-aggregate distance.
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Affiliation(s)
- Sylvain Prevost
- ESRF - The European Synchrotron, 71 avenue des Martyrs, 38000 Grenoble, France
| | - Tobias Lopian
- Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257 (CEA/CNRS/UM2/ENCSM), 30207 Bagnols-sur-Cèze, France; Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Maximilian Pleines
- Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257 (CEA/CNRS/UM2/ENCSM), 30207 Bagnols-sur-Cèze, France; Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Olivier Diat
- Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257 (CEA/CNRS/UM2/ENCSM), 30207 Bagnols-sur-Cèze, France
| | - Thomas Zemb
- Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257 (CEA/CNRS/UM2/ENCSM), 30207 Bagnols-sur-Cèze, France
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17
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Lopian T, Schöttl S, Prévost S, Pellet-Rostaing S, Horinek D, Kunz W, Zemb T. Morphologies Observed in Ultraflexible Microemulsions with and without the Presence of a Strong Acid. ACS CENTRAL SCIENCE 2016; 2:467-75. [PMID: 27504493 PMCID: PMC4965855 DOI: 10.1021/acscentsci.6b00116] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Indexed: 05/22/2023]
Abstract
We show that three different morphologies exist near the two-phase boundary of ternary systems containing a hydrotropic cosolvent. Based on synchrotron small- and wide-angle X-ray scattering combined with molecular dynamics, we rationalize the specific scattering signature of direct, bicontinuous, and reverse mesoscale solubilization. Surprisingly, these mesostructures are resilient toward strong acids, which are required in industrial applications. However, on a macroscopic scale, the phase boundary shifts in salting-in and salting-out in the direct and respectively reverse regime, leading to a crossing of the binodals.
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Affiliation(s)
- Tobias Lopian
- Institut
de Chimie Séparative de Marcoule, UMR 5257(CEA/CNRS/UM2/ENCSM), 30207 Bagnols sur
Cèze, France
- Institute
of Physical and Theoretical Chemistry, University
of Regensburg, 93040 Regensburg, Germany
| | - Sebastian Schöttl
- Institute
of Physical and Theoretical Chemistry, University
of Regensburg, 93040 Regensburg, Germany
| | - Sylvain Prévost
- ESRF—the
European Synchrotron Radiation Facility, 38000 Grenoble, France
| | - Stéphane Pellet-Rostaing
- Institut
de Chimie Séparative de Marcoule, UMR 5257(CEA/CNRS/UM2/ENCSM), 30207 Bagnols sur
Cèze, France
| | - Dominik Horinek
- Institute
of Physical and Theoretical Chemistry, University
of Regensburg, 93040 Regensburg, Germany
- E-mail:
| | - Werner Kunz
- Institute
of Physical and Theoretical Chemistry, University
of Regensburg, 93040 Regensburg, Germany
| | - Thomas Zemb
- Institut
de Chimie Séparative de Marcoule, UMR 5257(CEA/CNRS/UM2/ENCSM), 30207 Bagnols sur
Cèze, France
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18
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Witala M, Lages S, Nygård K. Mesoscale ordering in binary aqueous solvents induced by ion size asymmetry. SOFT MATTER 2016; 12:4778-4782. [PMID: 27112965 DOI: 10.1039/c6sm00580b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Surprising weak assembly behavior has lately been found in binary aqueous solvents containing antagonistic salt. The underlying mechanism is still under debate, particularly the role of ion size asymmetry. Here we use small-angle X-ray scattering to study the effect of ion size asymmetry on the mesoscale ordering in a binary solvent composed of water and 2,6-dimethylpyridine with added symmetrical quaternary ammonium salt. By systematically elongating the hydrocarbon side-chain lengths, and hence developing cation-to-anion size asymmetry, we provide the first experimental evidence of a gradual build-up of the solvent's mesoscale ordering. These results are in qualitative agreement with model-independent theoretical predictions.
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Affiliation(s)
- Monika Witala
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-41296 Gothenburg, Sweden.
| | - Sebastian Lages
- MAX IV Laboratory, Lund University, PO Box 118, SE-22100 Lund, Sweden
| | - Kim Nygård
- Department of Chemistry and Molecular Biology, University of Gothenburg, SE-41296 Gothenburg, Sweden.
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19
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Ciach A. Competition Between Electrostatic and Thermodynamic Casimir Potentials in Near-Critical Mixtures with Ions. ADVANCES IN BIOMEMBRANES AND LIPID SELF-ASSEMBLY 2016. [DOI: 10.1016/bs.abl.2015.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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20
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Sin JS, Pak HC, Sin CS. Influence of asymmetric depletion of solvents on the electric double layer of charged objects in binary polar solvent mixtures. Phys Chem Chem Phys 2016; 18:26509-26518. [DOI: 10.1039/c6cp05358k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ratio of the dipole moment to the volume of solvent is the key factor for asymmetric depletion of solvents.
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Affiliation(s)
- Jun-Sik Sin
- Department of Physics
- Kim Il Sung University
- Taesong District
- DPR Korea
| | - Hak-Chol Pak
- Department of Physics
- Kim Il Sung University
- Taesong District
- DPR Korea
| | - Chung-Sik Sin
- Department of Physics
- Kim Il Sung University
- Taesong District
- DPR Korea
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21
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Uematsu Y. Electrophoresis of electrically neutral porous spheres induced by selective affinity of ions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:022303. [PMID: 25768501 DOI: 10.1103/physreve.91.022303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Indexed: 06/04/2023]
Abstract
I investigate the possibility that electrically neutral porous spheres electrophorese in electrolyte solutions with asymmetric affinity of ions to spheres on the basis of electrohydrodynamics and the Poisson-Boltzmann and Debye-Bueche-Brinkman theories. Assuming a weak electric field and ignoring the double-layer polarization, I obtain analytical expressions for electrostatic potential, electrophoretic mobility, and flow field. In the equilibrium state, the Galvani potential forms across the interface of the spheres. Under a weak electric field, the spheres show finite mobility with the same sign as the Galvani potential. When the radius of the spheres is significantly larger than the Debye and hydrodynamic screening length, the mobility monotonically increases with increasing salinity.
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Affiliation(s)
- Yuki Uematsu
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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22
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Marcus J, Touraud D, Prévost S, Diat O, Zemb T, Kunz W. Influence of additives on the structure of surfactant-free microemulsions. Phys Chem Chem Phys 2015; 17:32528-38. [DOI: 10.1039/c5cp06364g] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In surfactant-free microemulsions, the combination ethanol/antagonistic salt behaves like a surfactant.
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Affiliation(s)
- J. Marcus
- Institute of Physical and Theoretical Chemistry
- University of Regensburg
- 93040 Regensburg
- Germany
| | - D. Touraud
- Institute of Physical and Theoretical Chemistry
- University of Regensburg
- 93040 Regensburg
- Germany
| | - S. Prévost
- ESRF
- The European Synchrotron
- 38000 Grenoble
- France
| | - O. Diat
- Institut de Chimie Séparative de Marcoule
- UMR 5257 (CEA/CNRS/UM/ENSCM)
- 30207 Bagnols sur Cèze
- France
| | - T. Zemb
- Institut de Chimie Séparative de Marcoule
- UMR 5257 (CEA/CNRS/UM/ENSCM)
- 30207 Bagnols sur Cèze
- France
| | - W. Kunz
- Institute of Physical and Theoretical Chemistry
- University of Regensburg
- 93040 Regensburg
- Germany
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23
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Colla T, Likos CN, Levin Y. Equilibrium properties of charged microgels: A Poisson-Boltzmann-Flory approach. J Chem Phys 2014; 141:234902. [DOI: 10.1063/1.4903746] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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24
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Pousaneh F, Ciach A. The effect of antagonistic salt on a confined near-critical mixture. SOFT MATTER 2014; 10:8188-8201. [PMID: 25171785 DOI: 10.1039/c4sm01264j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We consider a near-critical binary mixture with addition of antagonistic salt (hydrophilic cations and hydrophobic anions) confined between weakly charged and selective surfaces. A mesoscopic functional for this system is developed from a microscopic description by a systematic coarse-graining procedure. The functional reduces to the Landau-Brazovskii functional for amphiphilic systems for a sufficiently large ratio between the correlation length in the critical binary mixture and the screening length. Our theoretical result agrees with the experimental observation [Sadakane et al., J. Chem. Phys., 2013, 139, 234905] that the antagonistic salt and the surfactant both lead to a similar mesoscopic structure. For very low salt concentration ρion the Casimir potential is the same as in the presence of inorganic salt. For larger ρion the Casimir potential takes a minimum followed by a maximum for separations of order of tens of nanometers, and exhibits an oscillatory decay very close to the critical point. For separations of tens of nanometers the potential between surfaces with a linear size of hundreds of nanometers can be of order of kBT. We have verified that in the experimentally studied samples [Sadakane et al., J. Chem. Phys., 2013, 139, 234905, Leys et al., Soft Matter, 2013, 9, 9326] the decay length is too small compared to the period of oscillations of the Casimir potential, but the oscillatory force could be observed closer to the critical point.
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Affiliation(s)
- Faezeh Pousaneh
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, PL-01-224 Warsaw, Poland.
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25
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Lamellar/Disorder Phase Transition in a Mixture of Water/2,6-Dimethylpyridine/Antagonistic Salt. J SOLUTION CHEM 2014. [DOI: 10.1007/s10953-014-0240-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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26
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Samin S, Tsori Y. Stabilization of charged and neutral colloids in salty mixtures. J Chem Phys 2013; 139:244905. [DOI: 10.1063/1.4851477] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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27
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Sadakane K, Nagao M, Endo H, Seto H. Membrane formation by preferential solvation of ions in mixture of water, 3-methylpyridine, and sodium tetraphenylborate. J Chem Phys 2013; 139:234905. [DOI: 10.1063/1.4838795] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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28
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Levy A, Andelman D, Orland H. Dipolar Poisson-Boltzmann approach to ionic solutions: A mean field and loop expansion analysis. J Chem Phys 2013; 139:164909. [DOI: 10.1063/1.4826103] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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29
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Dang MT, Verde AV, Nguyen VD, Bolhuis PG, Schall P. Temperature-sensitive colloidal phase behavior induced by critical Casimir forces. J Chem Phys 2013; 139:094903. [DOI: 10.1063/1.4819896] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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30
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Haramaki H, Shimomura T, Umecky T, Takamuku T. SANS, Infrared, and 7Li and 23Na NMR Studies on Phase Separation of Alkali Halide–Acetonitrile–Water Mixtures by Cooling. J Phys Chem B 2013; 117:2438-48. [DOI: 10.1021/jp309881v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Hiroki Haramaki
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Takuya Shimomura
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Tatsuya Umecky
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Toshiyuki Takamuku
- Department of Chemistry
and Applied Chemistry, Faculty
of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
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31
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Sadakane K, Horikawa Y, Nagao M, Seto H. The Effect of Tetraphenylphosphonium Chloride on Phase Behavior and Nanoscale Structures in a Mixture of D2O and 3-Methylpyridine. CHEM LETT 2012. [DOI: 10.1246/cl.2012.1075] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Koichiro Sadakane
- KENS&CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization
| | - Yuka Horikawa
- Institute for Solid State Physics, The University of Tokyo
| | - Michihiro Nagao
- NIST Center for Neutron Research, National Institute of Standards and Technology
- Center for Exploration of Energy and Matter, Indiana University
| | - Hideki Seto
- KENS&CMRC, Institute of Materials Structure Science, High Energy Accelerator Research Organization
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32
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Abstract
Abstract
The influence of dilute impurities on the structure of a fluid solvent is investigated theoretically. General arguments, which do not rely on particular models, are used to derive an extension of the Ornstein–Zernike form for the solvent structure factor at small scattering vectors. It is shown that dilute impurities can influence the solvent structure only if they are composed of ions with significantly different sizes. Non-ionic impurities or ions of similar size are shown to not alter the solvent structure qualitatively. This picture is compatible with available experimental data. The derived form of the solvent structure factor is expected to be useful to infer information on the impurity-solvent interactions form measured scattering intensities.
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Affiliation(s)
- Markus Bier
- Max-Planck-Institut für Intelligente Systeme, Stuttgart, Deutschland
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33
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Bier M, Gambassi A, Dietrich S. Local theory for ions in binary liquid mixtures. J Chem Phys 2012; 137:034504. [DOI: 10.1063/1.4733973] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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34
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Kumar R, Sumpter BG, Kilbey SM. Charge regulation and local dielectric function in planar polyelectrolyte brushes. J Chem Phys 2012; 136:234901. [DOI: 10.1063/1.4729158] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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35
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Cañas-Marín WA. Thermodynamics of Nonferroelectric Mixtures under the Influence of Electrostatic Fields. Ind Eng Chem Res 2012. [DOI: 10.1021/ie3002149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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36
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Okamoto R, Onuki A. Casimir amplitudes and capillary condensation of near-critical fluids between parallel plates: Renormalized local functional theory. J Chem Phys 2012; 136:114704. [DOI: 10.1063/1.3693331] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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37
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Onuki A, Okamoto R. Selective solvation effects in phase separation in aqueous mixtures. Curr Opin Colloid Interface Sci 2011. [DOI: 10.1016/j.cocis.2011.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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38
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Okamoto R, Onuki A. Charged colloids in an aqueous mixture with a salt. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:051401. [PMID: 22181411 DOI: 10.1103/physreve.84.051401] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Indexed: 05/31/2023]
Abstract
We calculate the ion and composition distributions around colloid particles in an aqueous mixture, accounting for preferential adsorption, electrostatic interaction, selective solvation among ions and polar molecules, and composition-dependent ionization. On the colloid surface, we predict a precipitation transition induced by a strong preference of hydrophilic ions to water and a prewetting transition between weak and strong adsorption and ionization. These transition lines extend far from the solvent coexistence curve in the plane of the interaction parameter χ (or the temperature) and the average solvent composition. The colloid interaction is drastically altered by these phase transitions on the surface. In particular, the interaction is much amplified on bridging of wetting layers formed above the precipitation line. Such wetting layers can either completely or partially cover the colloid surface depending on the average solvent composition.
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Affiliation(s)
- Ryuichi Okamoto
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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39
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Onuki A, Araki T, Okamoto R. Solvation effects in phase transitions in soft matter. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:284113. [PMID: 21709322 DOI: 10.1088/0953-8984/23/28/284113] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Phase transitions in polar binary mixtures can be drastically altered by even a small amount of salt. This is because the preferential solvation strongly depends on the ambient composition. Together with a summary of our research on this problem, we present some detailed results on the role of antagonistic salt composed of hydrophilic and hydrophobic ions. These ions tend to segregate at liquid-liquid interfaces and selectively couple to water-rich and oil-rich composition fluctuations, leading to mesophase formation. In our two-dimensional simulation, the coarsening of the domain structures can be stopped or slowed down, depending on the interaction parameter (or the temperature) and the salt density. We realize stripe patterns at the critical composition and droplet patterns at off-critical compositions. In the latter case, charged droplets emerge with considerable size dispersity in a percolated region. We also give the structure factors among the ions, accounting for the Coulomb interaction and the solvation interaction mediated by the composition fluctuations.
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Affiliation(s)
- Akira Onuki
- Department of Physics, Kyoto University, Kyoto, Japan.
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40
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Onuki A, Okamoto R, Araki T. Phase Transitions in Soft Matter Induced by Selective Solvation. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2011. [DOI: 10.1246/bcsj.20110012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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41
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Affiliation(s)
- Sela Samin
- Department of Chemical Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel
| | - Yoav Tsori
- Department of Chemical Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, 84105 Beer-Sheva, Israel
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42
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Okamoto R, Onuki A. Precipitation in aqueous mixtures with addition of a strongly hydrophilic or hydrophobic solute. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:051501. [PMID: 21230480 DOI: 10.1103/physreve.82.051501] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Indexed: 05/30/2023]
Abstract
We examine phase separation in aqueous mixtures due to preferential solvation with a low-density solute (hydrophilic ions or hydrophobic particles). For hydrophilic ions, preferential solvation can stabilize water domains enriched with ions. This precipitation occurs above a critical solute density n(p) in wide ranges of the temperature and the average composition, where the mixture solvent would be in a one-phase state without solute. The volume fraction of precipitated domains tends to zero as the average solute density n is decreased to np or as the interaction parameter χ is decreased to a critical value χ(p). If we start with one-phase states with n>n(p) or χ>χ(p), precipitation proceeds via homogeneous nucleation or via heterogeneous nucleation, for example, around suspended colloids. In the latter case, colloid particles are wrapped by thick wetting layers. We also predict a first-order prewetting transition for n or χ slightly below np or χ(p) for neutral colloids.
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Affiliation(s)
- Ryuichi Okamoto
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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43
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Ciach A, Maciołek A. Distribution of ions near a charged selective surface in critical binary solvents. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:041127. [PMID: 20481697 DOI: 10.1103/physreve.81.041127] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Indexed: 05/29/2023]
Abstract
Near-critical binary mixtures containing ionic solutes near a charged wall preferentially adsorbing one component of the solvent are studied. Within the Landau-Ginzburg approach extended to include electrostatic interactions and the chemical preference of ions for one component of the solvent, we obtain a simple form for the leading-order correction to the Debye-Hückel theory result for the charge density profile. Our result shows that critical adsorption influences significantly distribution of ions near the wall. This effect may have important implications for the screening of electrostatic interactions between charged surfaces immersed in binary near-critical solvents.
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Affiliation(s)
- Alina Ciach
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, PL-01-224 Warsaw, Poland
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44
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Samin S, Tsori Y. Stability of binary mixtures in electric field gradients. J Chem Phys 2010; 131:194102. [PMID: 19929041 DOI: 10.1063/1.3257688] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We consider the influence of electric field gradients on the phase behavior of nonpolar binary mixtures. Small fields give rise to smooth composition profiles, whereas large enough fields lead to a phase-separation transition. The critical field for demixing as well as the equilibrium phase-separation interface are given as a function of the various system parameters. We show how the phase diagram in the temperature-composition plane is affected by electric fields, assuming a linear or nonlinear constitutive relations for the dielectric constant. Finally, we discuss the unusual case where the interface appears far from any bounding surface.
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Affiliation(s)
- Sela Samin
- Department of Chemical Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
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45
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Szalai I, Nagy S, Dietrich S. Nonlinear dielectric effect of dipolar fluids. J Chem Phys 2009; 131:154905. [DOI: 10.1063/1.3248242] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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46
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Ben-Yaakov D, Andelman D, Harries D, Podgornik R. Beyond standard Poisson-Boltzmann theory: ion-specific interactions in aqueous solutions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:424106. [PMID: 21715841 DOI: 10.1088/0953-8984/21/42/424106] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The Poisson-Boltzmann mean-field description of ionic solutions has been successfully used in predicting charge distributions and interactions between charged macromolecules. While the electrostatic model of charged fluids, on which the Poisson-Boltzmann description rests, and its statistical mechanical consequences have been scrutinized in great detail, much less is understood about its probable shortcomings when dealing with various aspects of real physical, chemical and biological systems. These shortcomings are not only a consequence of the limitations of the mean-field approximation per se, but perhaps are primarily due to the fact that the purely Coulombic model Hamiltonian does not take into account various additional interactions that are not electrostatic in their origin. We explore several possible non-electrostatic contributions to the free energy of ions in confined aqueous solutions and investigate their ramifications and consequences on ionic profiles and interactions between charged surfaces and macromolecules.
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Affiliation(s)
- Dan Ben-Yaakov
- Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
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47
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Araki T, Onuki A. Dynamics of binary mixtures with ions: dynamic structure factor and mesophase formation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:424116. [PMID: 21715851 DOI: 10.1088/0953-8984/21/42/424116] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Dynamic equations are presented for polar binary mixtures containing ions in the presence of preferential solvation. In one-phase states, we calculate the dynamic structure factor of the composition accounting for ion motion. Microphase separation can take place for sufficiently large solvation asymmetry of the cations and the anions. We show two-dimensional simulation results of the mesophase formation with an antagonistic salt, where the cations are hydrophilic and the anions are hydrophobic. The structure factor S(q) in the resultant mesophase has a sharp peak at an intermediate wavenumber of the order of the Debye-Hückel wavenumber. As the quench depth is increased, the surface tension nearly vanishes in mesophases due to an electric double layer.
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Affiliation(s)
- Takeaki Araki
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
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48
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Sadakane K, Onuki A, Nishida K, Koizumi S, Seto H. Multilamellar structures induced by hydrophilic and hydrophobic ions added to a binary mixture of D2O and 3-methylpyridine. PHYSICAL REVIEW LETTERS 2009; 103:167803. [PMID: 19905726 DOI: 10.1103/physrevlett.103.167803] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2009] [Indexed: 05/28/2023]
Abstract
A phase transition is observed between a one-phase disordered phase and an ordered phase with multilamellar (onion) structures in an off-critical mixture of D2O and 3-methylpyridine (3MP) containing 85 mM of a salt in the absence of a surfactant. The salt consists of hydrophilic cations and hydrophobic anions that interact asymmetrically with the solvent composition fluctuations inducing mesophases. The structure factor of the composition distribution obtained from small-angle neutron scattering has a peak at an intermediate wave number in the disordered phase and multiple peaks in the ordered phase. Lamellar layers forming onions are composed of solvation-induced charged membranes swollen by D2O. The onion phase is realized only for small volume fractions of 3MP (in D2O-rich solvent).
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Affiliation(s)
- Koichiro Sadakane
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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49
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Tojo K, Furukawa A, Araki T, Onuki A. Defect structures in nematic liquid crystals around charged particles. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2009; 30:55-64. [PMID: 19756793 DOI: 10.1140/epje/i2009-10506-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 05/27/2009] [Accepted: 08/05/2009] [Indexed: 05/28/2023]
Abstract
We numerically study the orientation deformations in nematic liquid crystals around charged particles. We set up a Ginzburg-Landau theory with inhomogeneous electric field. If the dielectric anisotropy epsilon 1 is positive, Saturn-ring defects are formed around the particles. For epsilon 1< 0 , novel "ansa" defects appear, which are disclination lines with their ends on the particle surface. We find unique defect structures around two charged particles. To lower the free energy, oppositely charged particle pairs tend to be aligned in the parallel direction for epsilon 1> 0 and in the perpendicular plane for epsilon 1< 0 with respect to the background director. For identically charged pairs the preferred directions for epsilon 1> 0 and epsilon 1< 0 are exchanged. We also examine competition between the charge-induced anchoring and the short-range anchoring. If the short-range anchoring is sufficiently strong, it can be effective in the vicinity of the surface, while the director orientation is governed by the long-range electrostatic interaction far from the surface.
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Affiliation(s)
- K Tojo
- Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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50
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Zhou S, Solana JR. Progress in the Perturbation Approach in Fluid and Fluid-Related Theories. Chem Rev 2009; 109:2829-58. [DOI: 10.1021/cr900094p] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Shiqi Zhou
- State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China, and School of Physics Science and Technology, Central South University, Changsha, Hunan 410083, China
| | - J. R. Solana
- Applied Physics Department, University of Cantabria, 39005 Santander, Spain
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