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(O t Bu) 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.