Improving the “Livingness” of ATRP by Reducing Cu Catalyst Concentration

The mole percentage of dead chains ( T mol % ) was quantified in a normal Cu-mediated atom transfer radical polymerization (ATRP) of methyl acrylate with tris(2-pyridylmethyl)amine and tris[2-(dimethylamino)ethyl]amine as the ligands in acetonitrile. The value for T mol % significantly exceeded the values predicted for conventional termination between two radicals. The main reason for the additional loss of chain-end functionality was identified as a Cu I -induced catalytic radical termination (CRT). The mechanism proposed for this CRT involves the formation of highly active R–Cu II /L and/or H–Cu II /L intermediates which react with radicals to form dead chains and regenerate the Cu I activator. The contribution of CRT to the loss of terminal functionality can be significantly decreased by reducing [Cu I ] to <1 mM, according to recently developed new ATRP processes.