Modeling Gel Swelling Equilibrium in the Mean Field: From Explicit to Poisson-Boltzmann Models

We develop a double mean-field theory for charged macrogels immersed in electrolyte solutions in the spirit of the cell model approach. We first demonstrate that the equilibrium sampling of a single explicit coarse-grained charged polymer in a cell yields accurate predictions of the swelling equilib...

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Bibliographic Details
Published in:Physical review letters 2019-05, Vol.122 (20), p.208002-208002, Article 208002
Main Authors: Landsgesell, Jonas, Sean, David, Kreissl, Patrick, Szuttor, Kai, Holm, Christian
Format: Article
Language:English
Subjects:
Computer simulation
Equilibrium
Gels
Mean field theory
Molecular dynamics
Polymers
Swelling
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Summary:We develop a double mean-field theory for charged macrogels immersed in electrolyte solutions in the spirit of the cell model approach. We first demonstrate that the equilibrium sampling of a single explicit coarse-grained charged polymer in a cell yields accurate predictions of the swelling equilibrium if the geometry is suitably chosen and all pressure contributions have been incorporated accurately. We then replace the explicit flexible chain by a suitably modeled penetrable charged rod that allows us to compute all pressure terms within the Poisson-Boltzmann approximation. This model, albeit computationally cheap, yields excellent predictions of swelling equilibria under varying chain length, polymer charge fraction, and external reservoir salt concentrations when compared to coarse-grained molecular dynamics simulations of charged macrogels. We present an extension of the model to the experimentally relevant cases of pH-sensitive gels.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.122.208002