Density functional theory for charged fluids

Jiang, Jian; Ginzburg, Valeriy V.; Wang, Zhen‐Gang

doi:10.1039/c8sm00595h

Cited by 36 publications

(48 citation statements)

References 61 publications

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“…In this work, we use a polymer classical density functional theory (PDFT) based on our previous work 33 to study the interactions between two neutral hard walls induced by the polyelectrolytes/salt solutions. Our results show that the primary feature of the interaction profile is a short-range attraction followed by repulsion at larger distance.…”

Section: Introductionmentioning

confidence: 99%

On the origin of oscillatory interactions between surfaces mediated by polyelectrolyte solution

Jiang

Ginzburg

Wang

2019

The Journal of Chemical Physics

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We use a numerical implementation of polymer classical density functional theory with an incompressibility condition to study the system consisting of nonadsorbing polyelectrolytes confined by two planar surfaces and quantify the effective interaction between the two planar surfaces as a function of the polyelectrolyte and salt concentrations. Our results indicate that for the uncharged surfaces (and weakly charged surfaces), the effective interaction primarily consists of a short-range attraction due to the depletion followed by repulsion due to the electric double layer overlapping and electrostatic correlations. For salt-free and low salt concentration systems, the magnitude of the repulsion barrier is determined by the overlap between the electric double layers, while at relatively high salt concentrations, the magnitude of the repulsion barrier is determined by the electrostatic correlations. Due to the competition between the electric double layer and the electrostatic correlations, the magnitude of the repulsion barrier varies nonmonotonically. In contrast, a mean-field Poisson-Boltzmann treatment of the electrostatics predicts a monotonically decreasing repulsion barrier with increasing salt concentration. At moderate salt concentrations, our theory predicts oscillatory interaction profiles. A comparison with the mean-field Poisson-Boltzmann treatment of electrostatics suggests that the oscillations are due primarily to electrostatic correlations.

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Section: Introductionmentioning

confidence: 99%

On the origin of oscillatory interactions between surfaces mediated by polyelectrolyte solution

Jiang

Ginzburg

Wang

2019

The Journal of Chemical Physics

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“…It is not at all clear that Maxwell’s equations joined with constitutive equations; and boundary conditions always have steady state solutions in the sinusoidal case. The Maxwell equations joined with diffusion and convection equations (like Navier–Stokes [ 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 ] or PNP

Poisson Nernst Planck

drift diffusion [ 52 , 53 , 55 , 57 , 59 , 61 , 123 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 ]) certainly do not always have solutions that are linear functions of just the electric field [ 146 , 147 , 148 , 149 ].”…”

Section: Discussion: From Electrodynamics To Biophysics and Backmentioning

confidence: 99%

Maxwell Equations without a Polarization Field, Using a Paradigm from Biophysics

Eisenberg

2021

Entropy

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When forces are applied to matter, the distribution of mass changes. Similarly, when an electric field is applied to matter with charge, the distribution of charge changes. The change in the distribution of charge (when a local electric field is applied) might in general be called the induced charge. When the change in charge is simply related to the applied local electric field, the polarization field P is widely used to describe the induced charge. This approach does not allow electrical measurements (in themselves) to determine the structure of the polarization fields. Many polarization fields will produce the same electrical forces because only the divergence of polarization enters Maxwell’s first equation, relating charge and electric forces and field. The curl of any function can be added to a polarization field P without changing the electric field at all. The divergence of the curl is always zero. Additional information is needed to specify the curl and thus the structure of the P field. When the structure of charge changes substantially with the local electric field, the induced charge is a nonlinear and time dependent function of the field and P is not a useful framework to describe either the electrical or structural basis-induced charge. In the nonlinear, time dependent case, models must describe the charge distribution and how it varies as the field changes. One class of models has been used widely in biophysics to describe field dependent charge, i.e., the phenomenon of nonlinear time dependent induced charge, called ‘gating current’ in the biophysical literature. The operational definition of gating current has worked well in biophysics for fifty years, where it has been found to makes neurons respond sensitively to voltage. Theoretical estimates of polarization computed with this definition fit experimental data. I propose that the operational definition of gating current be used to define voltage and time dependent induced charge, although other definitions may be needed as well, for example if the induced charge is fundamentally current dependent. Gating currents involve substantial changes in structure and so need to be computed from a combination of electrodynamics and mechanics because everything charged interacts with everything charged as well as most things mechanical. It may be useful to separate the classical polarization field as a component of the total induced charge, as it is in biophysics. When nothing is known about polarization, it is necessary to use an approximate representation of polarization with a dielectric constant that is a single real positive number. This approximation allows important results in some cases, e.g., design of integrated circuits in silicon semiconductors, but can be seriously misleading in other cases, e.g., ionic solutions.

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“…We particularly focused on mean-field theories and only briefly mentioned molecular simulations, as most simulations of weak PE so far are focused on weak PE in solution and not on weak polyelectrolyte near interfaces or confined dense spaces; the subject on this paper. We like to mention that there exist several other theoretical approaches to describe tethered polymers such as classical density-functional theory and PRISM-like theories [ 212 , 213 ]. However, as these theories have only been applied to strong polyelectrolytes so far [ 141 , 214 ], we did not discuss them here.…”

Section: Discussionmentioning

confidence: 99%

“…Theoretical description of short-range electrostatic correlations beyond mean-field have been developed for strong polyelectrolytes in solution and melts. See, for example, in [ 212 , 217 , 218 , 219 , 220 , 221 ]. However, so far, none of these approaches have been extended or applied to tethered weak polyelectrolytes.…”

Section: Discussionmentioning

confidence: 99%

Theoretical Modeling of Chemical Equilibrium in Weak Polyelectrolyte Layers on Curved Nanosystems

et al. 2020

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Surface functionalization with end-tethered weak polyelectrolytes (PE) is a versatile way to modify and control surface properties, given their ability to alter their degree of charge depending on external cues like pH and salt concentration. Weak PEs find usage in a wide range of applications, from colloidal stabilization, lubrication, adhesion, wetting to biomedical applications such as drug delivery and theranostics applications. They are also ubiquitous in many biological systems. Here, we present an overview of some of the main theoretical methods that we consider key in the field of weak PE at interfaces. Several applications involving engineered nanoparticles, synthetic and biological nanopores, as well as biological macromolecules are discussed to illustrate the salient features of systems involving weak PE near an interface or under (nano)confinement. The key feature is that by confining weak PEs near an interface the degree of charge is different from what would be expected in solution. This is the result of the strong coupling between structural organization of weak PE and its chemical state. The responsiveness of engineered and biological nanomaterials comprising weak PE combined with an adequate level of modeling can provide the keys to a rational design of smart nanosystems.

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Density functional theory for charged fluids

Cited by 36 publications

References 61 publications

On the origin of oscillatory interactions between surfaces mediated by polyelectrolyte solution

On the origin of oscillatory interactions between surfaces mediated by polyelectrolyte solution

Maxwell Equations without a Polarization Field, Using a Paradigm from Biophysics

Theoretical Modeling of Chemical Equilibrium in Weak Polyelectrolyte Layers on Curved Nanosystems

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