Time-resolved investigation of early processes in the reduction of Ag+ on polyacrylate in aqueous solution

Aqueous solutions of AgClO4 (4 x 10(-4) to 10(-2) M) and sodium polyacrylate (0.1 M, mean chain length of 30) are exposed to a pulse of high-energy radiation, and the changes in optical absorption are recorded in the time range from microseconds to seconds. The reduction of Ag+ by the hydrated electron is slowed by the polyanion, whereas the subsequent reaction of Ag-0 with Ag+ is practically not affected. Polymer-bound Ag-2(+) has two absorption bands (310 and 440 nm). The formation of Ag-3(2+) in the reaction of Ag-2(+) with Ag+ is strongly retarded by the polyanion; it occurs in an interchain process at low Ag+ concentrations and probably also as an intrachain process at higher ones. Polymer-bound Ag-3(2+) has a broad UV absorption tailing into the visible. At longer times after the pulse (up to seconds), bimolecular interchain processes take place in which colored complexes are formed, which at first contain a small number of silver atoms and an approximately equal number of Ag+ ions, and are stabilized by the polyanion chains.