STABILITY OF INTERPOLYELECTROLYTE COMPLEX ES IN AQUEOUS SALINE SOLUTIONS - EFFECT OF THE DEGREE OF POLYMERIZATION OF POLYIONS

Dissociative stability of interpolyelectrolyte complexes formed by flu orescently labeled polymethacrylate anions and poly(N-ethyl-4-vinylpyr idinium) cations was studied in aqueous salt-containing solutions by f luorescence quenching and velocity sedimentation. It was shown that th e dissociation of polyelectrolyte complexes in which the degree of pol ymerization of polyanion is greater than the degree of polymerization of polycation begins at a certain critical concentration of the salt i n solution and proceeds by gradual expulsion of polycations from the c omplex. It was found that the critical concentration of low-molecular- mass electrolyte increases with an increase in the chain length of pol ycation and is almost independent of the degree of polymerization of p olyanion and of the initial composition of interpolyelectrolyte comple x. A model that correlates the critical concentration of salt with the fraction of salt bonds that have dissociated in the complex was sugge sted. Within the framework of this model, the need to consider coopera tivity of the dissociation of interpolymer salt bonds was demonstrated .