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Ionic equilibria and swelling of soft permeable particles in electrolyte solutions


We discuss osmotic equilibria between soft permeable particles, of radius $R$ and volume charge density $\rho$, and bulk electrolyte solutions of the inverse Debye length $\kappa$. Existing models are based on a simplifying assumption of weakly charged particles. Here we derive analytical approximations for a distribution of a potential, ions and pressure in the system, suitable even when $\rho$ is quite large. Our theory is valid not only for ``large'' particles ($\kappa R \gg 1$), where a central part is fully screened, but also for weakly screened ``small'' particles ($\kappa R \leq 1$) with overlapping inner diffuse layers. Besides, we present novel coarse-grained simulations to validate the analysis and illustrate the variation of potential/ions profiles in response to changes in $\kappa R$ and $\rho$. 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.

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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, 2019, Accepted Manuscript

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    Ionic equilibria and swelling of soft permeable particles in electrolyte solutions

    E. Silkina, T. Y. Molotilin, S. R. Maduar and O. I. Vinogradova, Soft Matter, 2019, Accepted Manuscript , DOI: 10.1039/C9SM01602C

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