Polyelectrolyte complexes in solution and in bulk

The review surveys the thermodynamics, kinetics and reaction mechanisms of oppositely charged polyelectrolytes in aqueous solutions giving rise to insoluble stoichiometric or soluble non-stoichiometric interpolyelectrolyte complexes. The mechanisms of polyelectrolyte exchange reactions are discussed. Equilibrated non-stoichiometric interpolyelectrolyte complexes show a dual behaviour in aqueous solutions. On the one hand, they behave as usual linear polyelectrolytes and, on the other hand, they exhibit properties of amphiphilic block copolymers. The addition of low-molecular-weight salts to solutions of interpolyelectrolyte complexes usually leads to redistribution of electrostatically bound chains and phase separation. Analysis of these processes is of key importance in assigning these complexes to a special family of polymeric materials. Selected data on the conformations of polyions in solid interpolyelectrolyte complexes are given and their thermomechanical properties in the swollen state are considered.