Monte Carlo simulation of polyelectrolyte gels: Effects of polydispersity and topological defects

Volumes and other structural properties of polyelectrolyte gels in equilibrium with pure water have been determined by Monte Carlo simulations. The role of chain length polydispersity and topological network defects of four different networks with varying cross-linking density, monomer charge, and chain stiffness have been investigated. Generally, a chain length polydispersity reduced the gel volume, whereas the presence of chains with one end detached from the cross-linker (severed chains) led to an increased gel volume. Polyelectrolyte networks displayed the largest and uncharged polymer networks the smallest dependence on chain length polydispersity. The effect of severed chains was strongest for flexible polyelectrolyte gels and weakest for uncharged networks and stiff polyelectrolyte gels. Mechanical properties of uncharged and charged polymer gels were also investigated through uniaxially stretching and compared with theory.