From synthesis of silver nanoparticles to polymer nanocomposites

Abstract

The regularities of formation of silver nanoparticles with a shell of coordinatively bound monocarboxylate ligands in a one-step synthesis by the reaction of low-temperature reduction of precursors, that is, silver alkyl- and oligostyrylmonocarboxylates, with triethylamine, diepoxy oligomer ED-20, and polyurethane prepolymer, were studied. A single mechanism of formation of silver nanoparticles through the dissolution of precursors in reducing agents by the reaction of formation of diphilic complexes between silver monocarboxylate molecules organized in micelles and electron-donor groups of reducing agents with a subsequent reduction reaction and self-assembly of nanoparticles was determined, which ensures the preservation of the spherical shape, small sizes (d ≈ 2–8 nm), and narrow dispersions: Ag⁺ → Ag⁰ → (Ag⁰)_n. Based on the determined mechanism, we propose a strategy for the preparation of polymer nanocomposites by curing with amines a pre-prepared modified binder consisting of epoxy resin ED-20 or polyurethane prepolymer, silver nanoparticles, and unreacted silver oligostyrylmonocarboxylate. The limiting concentration of the precursor in the modified binder, at which a uniform distribution of silver nanoparticles within the bulk of the nanocomposites is achieved, was determined. It is shown that silver nanoparticles slightly reduce the glass transition temperature and do not affect the mechanical properties of epoxy nanocomposites. The termophysical properties of the nanocomposites depend on the topology of the epoxy matrix.