Controlled Radical Polymerization Utilizing Preformed Metal Complexes Based on Substituted Bipyridines and Terpyridines

Metal complexes based on different substituted dimethyl-2,2'-bipyridines and 5,5"-dimethyl-2,2':6',2"-terpyridine were used in combination with aluminium isopropoxide for the controlled radical polymerization of styrene, acrylate and methacrylate derivatives. Depending on the substitution pattern and the central metal ion the effectivity of the systems revealed distinct differences. The control over molecular weight, molecular weight distribution and reaction rate depends strongly on the choice of central metal ion and the ligand system. Best results concerning control of molecular weight and molecular weight distribution for styrene and acrylates were obtained using a combination of [Cu(II)(4,4'-dimethyl-2,2'-bipyridine)3](PF6)2, aluminium isopropoxide, (1-bromoethyl)benzene as initiator and acetonitrile as solvent at 75°C. Furthermore, the polymers obtained were colorless with a very low content of residual metal ions. Using this polymerization system, defined block copolymers and other special architectures are accessible.