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

Abstract

An electrochemically controlled synthesis of multiblock copolymers by alternating the redox states of (salfan)Zr(O^tBu)₂ (salfan = 1,1'-di(2-<i>tert</i>-butyl-6-<i>N</i>-methylmethylenephenoxy)ferrocene) is reported. Aided by electrochemistry with a glassy carbon working electrode, an <i>in situ</i> 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-<i>b</i>-lactide-<i>b</i>-cyclohexene oxide-<i>b</i>-lactide), and an ABC triblock copolymer, poly(hydroxybutyrate-<i>b</i>-cyclohexene oxide-<i>b</i>-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.