Journal of the American Chemical Society, Vol.140, No.17, 5686-5690, 2018
Electrochemically Switchable Ring-Opening Polymerization of Lactide and Cyclohexene Oxide
An electrochemical method was developed for the redox switchable polymerization of lactide and cyclohexene oxide. Using a lithium reversible sacrificial electrode and a high surface area carbon working electrode, efficient transformation between formally iron (II) and iron(III) oxidation states of a bis(imino)pyridine iron alkoxide complex was possible, which led to the ability to activate the complex for ring opening polymerization reactions. In addition to serving as a redox trigger, an electrochemical toggle switch was developed in which the chemoselectivity for lactide and epoxide polymerization was altered in situ. These findings led to the synthesis of poly(lactic acid-b-cyclohexene oxide) block copolymers in which the sequence of monomers incorporated is controlled by the electrical potential applied.