Controlled/“living” radical polymerization of methyl methacrylate catalyzed by CpCo(I) complexes conveniently generated from cobaltocene in situ

Atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by a series of exo-substituted η4-cyclopentadiene CpCo(I) complexes generated conveniently from cobaltocene in situ was studied. It is found that the steric and electronic effects of the exo-substituents at the η4-cyclopentadiene ligand have significant effects on the polymerization. More bulky or weaker electron-withdrawing substituents lead to higher polymerization rate and better initiation efficiency. Polymerization of styrene, and the block copolymerization of MMA with styrene were also studied, using the selected catalyst system.