Improvement on stability of polymeric latexes prepared by emulsion ATRP through copper removal using electrolysis

Copper contamination results in poor stability and limited application of latexes generated using emulsion ATRP. This work describes an electrolysis method, which provides for the removal of copper from such latexes, while preserving colloidal stability and latex particle integrity. Polyacrylate latexes were synthesized via emulsion polymerization with reverse ATRP. The reaction was mediated by CuCl2/4,4-di-(5-nonyl)-2,2′-bipyridine (dNbpy) and stabilized with a combined surfactant system of Brij-98 and a new surfactant-ligand (SL) design, which provides for the capture Cu species residing at the interface of latex particles. It is shown that >98% of the residual Cu was removed after 14-h of electrolysis at a voltage of 3 V, and >99% Cu removal was achieved after 7-h treatment at 9 V. For comparison, a Cu removal of <50% was measured in polyacrylate latexes prepared by emulsion ATRP using dNbpy as a sole ligand. The removal of Cu using this process is shown to be rapid and efficient and provide for a substantial increase in latex stability and weather resistance of polymers.