Coarse-grained simulations of polyelectrolyte brushes using a hybrid model

We investigate the structure of polyelectrolyte brushes to determine the effects of the charge fraction of the polymers, grafting density, chain length, and salt concentration. A hybrid coarse-grained model is employed, where a soft potential is applied to coarse-grained particles representing the solvent, while a hard potential is used for the polymer beads, and co- and counterions. A steep increase in brush height with charge fraction is observed in the low-to-moderate charge fraction regime, whereas the brush approaches the contour height in the high charge fraction regime. The effects of graft density and chain length on brush height are well explained by the scaling theory based on the balance between the osmotic pressure and chain elasticity, properly taking into account the polymer stiffness. In addition, Pincus's power law for varying added salt concentration is also reproduced by the simulation.