Ring-opening metathesis polymerization has emerged as a powerful controlled polymerization technique. State of the art metal alkylidene based initiators enable the synthesis of polymers with excellent control over parameters such as molecular weight, dispersity, and stereochemistry. Unfortunately, the use of metal-based initiators results in materials contaminated with residual metals which can limit applications in sensitive fields, and lead to downstream degradation of materials properties. To overcome these limitations the Boydston group developed a metal-free variant of ROMP (MF-ROMP) which uses enol ether initiators and pyrylium photocatalysts under visible light irradiation to access ROMP products. It’s hypothesized that MF-ROMP proceeds through radical cationic intermediates, therefore ion-pairing interactions present a tool to achieve control similar to metal-mediated ROMP. During this talk we’ll discuss our discovery and optimization of ion-pairing interactions which give rise to stereocontrol in MF-ROMP, and our mechanistic hypothesis for the origins of stereocontrol. Next, we’ll discuss the properties of materials synthesized with different stereochemistry. Finally, we’ll conclude by presenting a recent discovery which leverages ion-pairing effects to improve molecular weight control in MF-ROMP.

Ion-pairing effects in metal-free ring-opening metathesis polymerization

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