Living polymerization of carbodiimides initiated by copper(I) and copper(II) amidinate complexes

Various catalysts for the polymerization of carbodiimide have been investigated. In early studies, anionic polymerization techniques were employed, but the products obtained were low molecular weight oligomers. More recently, a living route using titanium(IV) complexes as initiators has been employed and the high molecular weight polymers obtained exhibit a well-ordered helical, extended chain conformation. However, the titanium complexes are sensitive to high temperatures and the presence of oxygen or water. Herein, we report that more robust catalysts based on copper(I) and copper(II) complexes also initiate living carbodiimide polymerizations. The tolerance of these complexes to impurities is illustrated by the fact that they cleanly initiate the polymerization of carbodiimides under air and oxygen. They are even active in the presence of water, but both molecular weights and yields tend to be lower than in dry solvents. It has been shown that the catalytic activity of a copper(II) amidinato complex is almost equal that of reported titanium(IV) initiators. Analysis of these systems by gel permeation chromatography-light scattering measurements (GPC-LS) and preliminary kinetic analysis suggest this system to be living.