Polyacrylates in the presence of an extraordinary monovalent cation—Solution behavior and metal nanoparticle formation

Sodium polyacrylate (NaPA) in dilute aqueous solution at an ionic strength of [NaNO₃] = 0.01M establishes a rich phase behavior in the presence of low amounts of silver cations, which were introduced at a few millimoles or less by replacing the corresponding amount of Na⁺ cations. Beyond an extremely low level of Ag⁺ cations, anionic PA chains aggregate. By increasing the concentration of Ag⁺, the aggregates become denser and keep on growing without limit. Once a certain range of [Ag⁺] is reached, the instantaneously formed dense aggregates remain stable. Irradiation of the PA aggregate solutions with UV-light induces formation of silver nanoparticles (Ag-Nps). Based on a combination of UV-vis spectroscopy, light scattering, transmission electron microscopy, and small angle neutron scattering, the mechanism of this NaPA assisted formation of Ag-Nps is studied. One focus of the study is lying on the effect of the two different solution states of dense aggregates, corresponding to the unstable growing AgPA aggregates and to the stable AgPA aggregates and another focus is aiming at the characterisation of the morphology of the generated hybrid particles composed of Ag-Nps and hosting PA chains.