Polyelectrolyte complex formation in highly aggregating systems. Effect of salt: response to subsequent addition of NaCl

Polyelectrolyte complex formation between polyanions and polycations with strong ionic groups and high molecular weights in pure water results in highly aggregated compact and nearly spherical particles, consisting of a neutralized core and a stabilizing shell of the excess component. The response of such systems to the addition of sodium chloride was studied by turbidimetry and static light scattering in relation to the ionic group of the polyanion (Na-poly(styrene sulfonate) and Na-poly(methacrylate)) and the charge density of the polycation (poly(diallyldimethylammonium chloride) and its copolymers with acrylamide). While in the systems with Na-PSS the addition of salt causes mainly additional aggregation and macroscopic flocculation, redissolution of the complexes with Na-PMA at a critical salt concentration was found. The use of the copolymers with hydrophilic acrylamide as excess component leads to a stabilization against additional aggregation.