Investigation of a zirconium compound for redox switchable ring opening polymerization.

A zirconium compound, (salfen)Zr(OiPr)2 (salfen = N,N'-bis(2,4-di-tert-butylphenoxy)-1,1'-ferrocenediimine), was tested as a redox switchable catalyst for the ring opening polymerization of cyclic esters and epoxides. Different activities were observed in the reduced and oxidized state, and an orthogonal switch on monomer activities could be achieved. Diblock and triblock copolymers were synthesized using an in situ redox switch of the catalyst oxidation state.