One-Pot Precision Synthesis of AB, ABA and ABC Block Copolymers via Switchable Catalysis

The switchable catalysis using a commercial salenMn catalyst was firstly developed and applied in the one-pot selective copolymerization from anhydrides, epoxides, CO₂ and ϵ-caprolactone (ϵ-CL) mixtures for the precise synthesis of AB, ABA and novel ABC block copolymers. The observed unique double switch process comprising three different polymerization cycles was rationalized by theoretical calculations. Surprisingly, the first block turned out to be an efficient macromolecular initiator for the consecutive introduction of carbonate linkages into copolymers, albeit with dominant cyclization with the catalyst alone. Further, through the selective reaction on different epoxides, the switchable copolymerization of up to five monomers was achieved yielding well-defined multi-block copolymers with structural diversity and functionality.