Hydrogels in Poor Solvents: A Molecular Dynamics Study

• Published in: Macromolecular theory and simulations 2011-09, Vol.20 (8), p.721-734
• Main Authors: Mann, Bernward A. F., Kremer, Kurt, Lenz, Olaf, Holm, Christian
• Format: Article
• Language: English
• Subjects: Applied sciences; Charging; Computer simulation; Exact sciences and technology; hydrogels; Mathematical models; molecular dynamics simulations; Monomers; Networks; Organic polymers; Physicochemistry of polymers; polyelectrolyte networks; Polyelectrolytes; poor solvents; Properties and characterization; Solution and gel properties; Solvents; Swelling
• ISSN: 1022-1344; 1521-3919; 1521-3919
• DOI: 10.1002/mats.201100050

The equilibrium swelling behavior of a crosslinked polyelectrolyte gel under poor‐solvent conditions is examined. To this end, MD simulations of a coarse‐grained network model with a diamond‐like topology are employed where the counterions are explicitly taken into account. A large range of different parameter combinations in the fraction f of charged monomers of the network, the strength of electrostatic interactions measured via the Bjerrum length $\ell _{{\rm B}} $, and various strand lengths are studied. The results agree with data on single PE chains, in particular the theoretically predicted pearl necklace conformations can be identified as well as a sausage‐like regime in the strong‐coupling region. MD simulations of coarse‐grained PE hydrogels in poor solvents are presented. The equilibrium swelling behavior of such gels for a large range of different parameter combinations of the fraction of charged monomers, the electrostatic interaction strength, and various strand lengths is studied. The counterion structure factor for poor‐solvent PEs is calculated and means to observe it experimentally are suggested.