ABC and ABAB Block Copolymers by Electrochemically Controlled Ring-Opening Polymerization

An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)­Zr­(OtBu)2 (salfan = 1,1′-di­(2-tert-butyl-6-N-methylmethylene­phenoxy)­ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an in situ potential switch alters the catalyst’s oxidation state and its subsequent monomer (l-lactide, β-butyrolactone, or cyclohexene oxide) selectivity in one pot. Various multiblock copolymers were prepared, including an ABAB tetrablock copolymer, poly­(cyclohexene oxide-b-lactide-b-cyclohexene oxide-b-lactide), and an ABC triblock copolymer, poly­(hydroxybutyrate-b-cyclohexene oxide-b-lactide). The polymers produced using this technique are similar to those produced via a chemical redox reagent method, displaying moderately narrow dispersities (1.1–1.5) and molecular weights ranging from 7 to 26 kDa.