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Ionic equilibria and swelling of soft permeable particles in electrolyte solutions

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Abstract

We discuss osmotic equilibria between soft permeable particles, of radius R and volume charge density ρ, and bulk electrolyte solutions of inverse Debye length κ. Existing models are based on a simplified assumption of weakly charged particles. Here we derive analytical approximations for the distribution of potentials, ions and pressure in a system, suitable even when ρ is quite large. Our theory is valid not only for “large” particles (κR ≫ 1), where the central part is fully screened, but also for weakly screened “small” particles (κR ≤ 1) with overlapping inner diffuse layers. Besides, we present novel coarse-grained simulations to validate the analysis and illustrate the variation of potential/ion profiles in response to changes in κR and ρ. Our simulations also allow us to argue that swelling of both “large” and “small” particles is uniform, although their inner non-uniform local pressure profiles are essentially and qualitatively different. These results are directly relevant for a variety of permeable charged objects, from polymer micro- and nanogels to more rigid porous colloids.

Graphical abstract: Ionic equilibria and swelling of soft permeable particles in electrolyte solutions

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Publication details

The article was received on 08 Aug 2019, accepted on 28 Nov 2019 and first published on 29 Nov 2019


Article type: Paper
DOI: 10.1039/C9SM01602C
Soft Matter, 2020, Advance Article

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    Ionic equilibria and swelling of soft permeable particles in electrolyte solutions

    E. F. Silkina, T. Y. Molotilin, S. R. Maduar and O. I. Vinogradova, Soft Matter, 2020, Advance Article , DOI: 10.1039/C9SM01602C

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