Cyclic Block Copolymers via Living Ring Expansion Metathesis Polymerization

Cyclic block copolymers are a captivating class of macromolecules with the potential for advanced materials applications due to their distinctive self-assembly behavior. Ring expansion metathesis polymerization (REMP) is a promising method towards such high molar mass cyclic polymers, but uncontrolled intermolecular ring-transfer processes have precluded its extension to cyclic block copolymers synthesis. As a result, the synthesis of cyclic block copolymers remains exceedingly rare. In this work, we develop a novel controlled living REMP method using cyclic Ru-benzylidene initiator Pyr-CB6. Using an operationally simple sequential monomer-addition strategy followed by thermally triggered intramolecular backbiting, we produce cyclic multiblock copolymers of low dispersity (