Equilibrium properties of charged microgels : a Poisson-Boltzmann-Flory approach

Abstract

The equilibrium properties of ionic microgels are investigated using a combination of the Poisson-Boltzmann and Flory theories. Swelling behavior, density profiles, and effective charges are all calculated in a self-consistent way. Special attention is given to the effects of salinity on these quantities. In accordance with the traditional ideal Donnan equilibrium theory, it is found that the equilibrium microgel size is strongly influenced by the amount of added salt. Increasing the salt concentration leads to a considerable reduction of the microgel volume, which therefore releases its internal material – solvent molecules and dissociated ions – into the solution. Finally, the question of charge renormalization of ionic microgels in the context of the cell model is briefly addressed.