Counterion binding to cationic polyelectrolytes in aqueous solution

The mean ion activity coefficient, (γ_±)_px/(γ_±)_salt for different high-linear charge density cationic polyelectrolyte fluoride, bromide, chloride and nitrate has been determined. The order found is: F^? > CI^? ≧ Br^? > NO. The results obtained with added nitrate were compared with those predicted by Iwasa, Guéron, and Weisbuch and Manning's models. The latter presents the best agreement for polyion chloride and bromide. It was possible to establish the most probable microconfiguration for the polyions studied here. Manning's theory gives a moderate agreement for polyion fluoride values compatible with a lower charge density than for polyelectrolyte chloride and bromide.