Copper triflate as a catalyst in atom transfer radical polymerization of styrene and methyl acrylate

The use of copper triflate complexes as catalysts for atom transfer radical polymerization (ATRP) of styrene and methyl acrylate (MA) is presented. The ability to start with Cu(OTf)(2) catalyst precursors allows for a simple experimental setup without catalyst oxidation. Reduction with copper(0) powder occurs quickly in most cases to form the copper(I) catalysts. The traditional bipyridine-based ATRP ligands were less efficient for styrene polymerization, but for methyl acrylate polymerization resulted in faster polymerizations relative to the CuBr analogues. The methylated triamine ligand was used for the Cu(OTf)(2)/Cu-0 system and also yielded good results for the polymerization of styrene (M-w/M-n = 1.10). This catalyst gave a rapid polymerization of MA with low polydispersities (M-w/M-n = 1.15) even at high conversions. The Cu(OTf) complexes are more active than their CuBr counterpart; however, this may be detrimental to having a controlled polymerization. In the case of styrene, it is possible that radical generation is too great, leading to termination through bimolecular coupling. For MA, molecular weights somewhat lower than predicted were observed and an exothermic reaction occurred in the presence of a molar excess of Cu-0. Lowering the amount of Cu-0 effectively lowers the amount of catalyst and allows for a well-controlled polymerization with a low contribution of termination reactions. Thus, Cu(OTf) complexes prepared from Cu(OTf)(2) in the presence of Cu-0 appear to be an-excellent catalytic species for styrene and MA polymerization especially with the methylated triamine ligand.