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

• Main Authors: Landsgesell, Jonas, Sean, David, Kreissl, Patrick, Szuttor, Kai, Holm, Christian
• Format: Journal Article
• Language: English
• Published: 13-05-2019
• Subjects: Physics - Soft Condensed Matter
• DOI: 10.48550/arxiv.1905.04960

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 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.