Ruthenium-initiated ring-opening metathesis polymerization (ROMP) remains an extraordinary tool for polymer synthesis due to its functional group tolerance, the ready availability of monomers and initiators, and the overall ease at which well-defined polymers can be rapidly synthesized. Nevertheless, the removal of trace ruthenium from the polymeric product remains a difficult task due to the wide scope of polymer compositions, the lack of a complete understanding of initiator decomposition, and the unknown identities of trace ruthenium products generated during ROMP. Beyond affecting the product's color and oxidative stability, trace ruthenium is a potential obstacle for the clinical translation of biomedically relevant polymers due to strict limits set by regulatory authorities.<br/><br/>Covalent capture, a purification methodology already proven useful for biomacromolecules, acts by selectively "capturing" the sole desired product from a complex mixture onto a solid support, allowing any and all impurities to be washed away. In this work, covalent capture purification was translated to ROMP due to its recognized potential to effect the removal of trace ruthenium from ROMP polymers. A ROMP terminator-decorated solid support was carefully designed to enable the methodology. In a single cascade metathesis event, the supported terminator simultaneously captures metathesis-active polymer onto the support and releases metathesis-inactive ruthenium into solution. The solid support is then thoroughly washed to remove all soluble impurities before cleaving the pristine polymer product from it. The methodology proved highly effective for ruthenium removal (&gt;99%) for a variety of linear polynorbornenes. Furthermore, through careful monitoring of trace ruthenium throughout the multistep purification, valuable insight about the nature of the ruthenium impurities was gathered.

Ruthenium removal from ring-opening metathesis polymerization via covalent capture purification

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