Removal of copper-based catalyst in atom transfer radical polymerization using different extraction techniques

Several methods allowing the removal of copper-based ATRP active complexes from crude amino-functionalized polymethacrylate chains are compared. Among them, precipitation in basic medium is one of the most efficient techniques since it allows high recovery yields (above 90%) with a residual metal content as low as 5 ppm. Extraction methods such as liquid-liquid phase separation and dialysis but also selective adsorption on acidic macroporous ion exchange resin constitute other attractive alternatives. As far as water-insoluble polymers are concerned, catalyst adsorption on alumina remains the most universal method and provides acceptable recovery efficiency. However, we want to stress the key-importance of the experimental adsorption conditions and above all the relative content of alumina used for catalyst extraction.