Bimetallic Cobalt Complex-Mediated Enantioselective Terpolymerizations of Carbon Dioxide, Cyclohexene Oxide, and β-Butyrolactone

Abstract

Enantioselective terpolymerization of carbon dioxide (CO2), cyclohexene oxide (CHO), and racemic β-butyrolactone (BBL) was first achieved in a one-pot reaction utilizing the catalyst system based on enantiopure bimetallic cobalt complex. The resultant terpolymers possess one high melting temperature (Tm) of more than 200 °C and a mixed glass transition temperature (Tg), which could be adjusted by CO2 pressure used in the terpolymerization. 1H NMR analysis indicated that the terpolymers had the carbonate-ester junction unit content in the range of 10.9-28.5%, dependent on CO2 pressure and CHO/BBL feed ratio. Combined with matrix-assisted laser desorption ionization time-of-flight mass spectrometry, two-dimensional NMR spectroscopy, 13C NMR spectroscopy, and polarimetry, an intramolecular bimetallic cooperation mechanism was proposed to be responsible for the terpolymerization process.