Molecular Dynamics Simulation of Nanocomposite-Polyelectrolyte Hydrogels

Nanocomposite-polyelectrolyte hydrogels are gels formed from a mixture of charged polymer chains and nanofillers. They have enhanced properties, can absorb large amounts of water, and potentially serve as a sustainable alternative to concrete for soil strengthening purposes. Despite the large number of studies on polyelectrolytes and their interactions with charged particles, little is known about the mechanism of network formation in a charged hydrogel system. Thus, we use molecular dynamics (MD) simulations to investigate the effect of charge distribution on the gelation of our system and related properties including viscosity; network formation; cluster geometry; and polymer adsorption onto filler particles. We used a coarse-grained approach where nanofillers were modeled as rigid disk-like platelets while polyelectrolytes were modeled as linear charged chains. System also included uncharged solvent particles and free-floating univalent counterions to ensure electroneutrality. Crosslinks were simulated by using pure Coulombic forces, as well as in a combination with physical forces. Our results show that the assembly of nanofillers is an important determinant of the physical properties of the gel mediated by the types of interactions between chains and nanofillers.