Silver ion reduction in non-aqueous liquid oligomers with terminal epoxy and amino groups for in situ synthesis of silver nanoparticles

Abstract

Silver nanoparticle (AgNP) formation in oligomers (epoxy resins and oligoxypropylenediamine) and epoxy–amine systems based on them were studied in detail using UV-visible spectroscopy, small-angle X-ray scattering, dynamic light scattering, and X-ray diffractometry. The reduction of silver ions in the oligomeric media was carried out at near-room temperatures, which is why it was called “cold”. A fundamental difference in the behaviour of Ag⁺ ions in oligomers, depending on the nature of their terminal groups, has been established, and assumptions have been made about the mechanism of stabilisation of Ag⁺ ions and nanoparticles based on reduced Ag⁰ silver atoms. The kinetics of Ag⁰ nanoparticle formation in epoxy systems has been the subject of investigation, and the influence of the system composition (precursor and solvent concentrations) on this process has been demonstrated. The evolution of Ag⁰ nanoparticle sizes in epoxy and epoxy–amine systems is discussed, and a hypothesis is put forward about the formation of an oligomeric hydrodynamic shell around these nanoparticles. It is suggested that, depending on the nature of the oligomer's terminal groups, this contributes to either the stabilisation or aggregation of nanoparticles. The present study investigates the influence of temperature on the ratio of Ag⁺ ion coordination/reduction processes and Ag⁰ nanoparticle stabilisation/aggregation. The results of this research will be used for the purpose of the targeted regulation of polymer–silver nanocomposite production processes.