Copper Removal in Atom Transfer Radical Polymerization

We have developed three methods for simple copper removal in atom transfer radical polymerization (ATRP). The first involved use of a polyethylene-ligand which is homogeneous under polymerization conditions, but precipitates upon cooling. Less than 1% of the original copper was left after simple decantation; however, long (24 h) polymerization times were observed. The second method involved the use of JandaJel™ ligands. Normal polymerization times were observed with this heterogeneous system, but copper removal was less efficient with 4-5% of the original copper remaining. The third method used precipiton ligands that are soluble in the cis-stilbene form, but precipitate when isomerized to the trans form. The precipitons were the most efficient at copper removal (<1% copper remaining), but cannot be recycled. For all three methods, ATRP was controlled as evidenced by monomer conversion and growth of molecular weight. We studied the polymerization of styrene, methyl methacrylate and N,N-dimethylaminoethyl methacrylate.