Controlled/"living" radical polymerization. Atom transfer radical polymerization using multidentate amine ligands

Three multidentate amines, tetramethylethylenediamine (TMEDA), N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA) and 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) have been successfully used as new ligands in the copper mediated atom transfer radical polymerization (ATRP) of styrene, methyl acrylate and methyl methacrylate. All the polymerizations were well controlled with a linear increase of molecular weights (M-n) with conversion and relatively low polydispersities throughout the reactions. Compared to the 2,2'-bipyridine (bipy) based ligands, most multidentate amines are less expensive and the polymerization mixtures are less colored. In particular, the use of the tridentate PMDETA and the tetradentate HMTETA as the ligands resulted in faster polymerization rates for styrene and methyl acrylate than those using bipy as the ligand. This may be in part attributed to the fact that the coordination complexes between copper and the simple amines have lower redox potentials than the copper-bipy complex, resulting in higher rates of activation of the dormant halides. Additional rate effects may originate from the solubilities of the copper(I) and copper(II) complexes. The new ligands are very attractive alternatives to bipy and its derivatives as ligands.