STUDY OF THE INTERACTION BETWEEN POLYACRYLATE AND SILVER OLIGOMER CLUSTERS

Gamma-radiolysis of aqueous solutions of silver sulfate in the presence of polyacrylic acid (PAH) or polyacrylate polyanion (PA-) allows the synthesis of a series of silver oligomer clusters which are observed through their UV-visible spectra. According to the experimental conditions (pH, PA/Ag ratio, dose, ageing), the spectral band characteristic for distinct silver cores is located at ca 280 (Ag-4(2+) cluster), 295 (a-type cluster), 335 (b-type), 370 (c-type) or 380 nm (subcolloidal particles). In part of the spectra, a second absorption band at higher wavelengths, mainly in the visible region, due to the polymer-silver interaction, has been studied and used to follow some reactions at the particle surface. A shift of this band upon ageing is understood in terms of slow reorganization of the polymer environment over days and months. At least two types of environment have been found. The competition of Cl- with PA- for the positive surface sites induces a weakening of the ligand bonding resulting in coalescence and/or increased corrodability.