Limiting stability temperatures for copper sols stabilized by poly(<Emphasis Type="Italic">N</Emphasis>-vinyllactams)

It has been shown that stable copper sols cannot be prepared through the reduction of copper ions in aqueous solutions of poly(N-vinyllactams) in the presence of poly(N-vinylpyrrolidone) in the temperature range 50–70°C, while in the presence of poly(N-vinylcaprolactam), the said sols cannot be prepared at temperatures below ～12°C. This tendency is related to the thermodynamic instability of complexes formed via noncovalent interactions of copper nanoparticles with polymer macromolecules in corresponding temperature ranges. Stable sols synthesized in the presence of the above polymers at other temperatures rapidly lose stability in the said temperature ranges, and this effect is accompanied by the aggregation of metal particles. The experimental results provide evidence that there is a relationship between the stability of complexes macromolecules-metal nanoparticles and the thermodynamic quality of the solvent.