Terpolymerization of β-Butyrolactone, Epoxides, and CO2: Chemoselective CO2-Switch and Its Impact on Kinetics and Material Properties

Terpolymerization reactions with a mixed-monomer feedstock of epoxides, CO2, and β-butyrolactone (BBL) at two different CO2 pressures are presented. The Lewis acidic zinc complex BDICF3–Zn–N(SiMe3)2 1 is able to catalyze both the ring-opening polymerization (ROP) of BBL and the ring-opening copolymerization of epoxides and CO2. The carbon dioxide concentration thereby displays an attractive tool for the chemoselective tailoring of the incorporation of both monomer types to either a block or a statistical configuration. A high CO2 pressure (40 bar) leads to a block structure, whereas 3 bar CO2 allows the two catalytic cycles, ROP of BBL and ring-opening copolymerization of cyclohexene oxide and CO2, to proceed with similar rates. This results in a statistical polymerization behavior. Reducing the CO2 pressure from 40 to 3 bar involves a change in the reaction order of CO2 from zero- to first-order dependency. The statistical polymerization pathway offers a promising route to terpolymers with one mixed-glas...