Year: 2026
Type: preprint
Abstract: 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 utilize newfound living characteristics of REMP with cyclic Ru-benzylidene initiator Pyr-CB6 to develop novel block copolymerization methodology. Using an operationally simple sequential monomer-addition strategy followed by thermally triggered intramolecular backbiting, we produce cyclic multiblock copolymers of low dispersity (<1.2) and high yields (up to 97%). Mechanistic analyses elucidate the delicate role that pyridine plays in the polymerization process. As a metathesis inhibitor, pyridine makes intermolecular ring-transfer prohibitively slow, but permits intramolecular backbiting when triggered. Overall, this study demonstrates the power of REMP with Pyr-CB6 as a vehicle towards a diverse future of cyclic block copolymer materials and applications.
Source: ChemRxiv
Authors: Lucy P Miller, Matthew R Golder
Institution: University of Washington
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7216275884