Dresden 2017 – wissenschaftliches Programm
CPP 56.6: Vortrag
Donnerstag, 23. März 2017, 12:00–12:15, ZEU 260
Modeling of Polyelectrolyte Gels in Equilibrium with Salt Solutions — Tobias Richter1, Peter Košovan2, Jonas Landsgesell1, and •Christian Holm1 — 1University of Stuttgart, Germany — 2Charles University in Prague, Czech Republic
We use hybrid molecular dynamics/Monte Carlo simulations and coarse-grained polymer models to study the swelling of polyelectrolyte gels in salt solutions. Besides existing industrial applications, such gels have been recently proposed as a promising agent for water desalination. We employ the semi-grand canonical ensemble to investigate partitioning of the salt between the bulk solution and the gel, and the salt-induced de-swelling of the gels under free swelling equilibrium and under compression. We compare our simulation data to the analytic model of Katchalsky and Michaeli which captures the deviations in the ion partitioning from the simple Donnan approximation fairly well . We modify the model by replacing the Gaussian elasticity with the Langevin function for finite extensibility and obtain nearly quantitative agreement between theory and simulations both for the swelling ratio and for the partitioning of salt, across the whole range of studied gel parameters and salt concentrations. The modified model provides a very good description of swelling of polyelectrolyte gels in salt solutions for charge densities up to a Manning parameter of one half. We use this improved model to construct a simple desalination cycle and to calculate the corresponding work to desalinate sea water to potable water.  P. Kosovan, T. Richter, C. Holm, Macromolecules 48, 7698-7708 (2015).