Stereoconvergent Chain-Growth Polymerization

The stereochemistry of polymers has a profound impact on their properties. Despite the well-developed stereoselective methods for prochiral vinyl monomers, current methods for racemic monomers are limited. Conventional approaches treat <i>sp</i> ^<i>3</i> chiral centers as immutable, resulting in poor atom-economical processes and limited control over enantioselectivity. This contrasts with stereoconvergent catalysis in small molecules, which has revolutionized synthesis by interrupting the transfer of chiral information from the substrate to the product, providing a clear platform for catalysts to access enantiopure compounds from racemic mixtures in up to 100% yield. Here we designed a catalyst that converges stereochemical information during polymerization, enabling access to asymmetric, isotactic polymers with quantitative atom economy from racemic feedstocks. The mechanism of stereoconvergence is accomplished by the catalyst ablating chiral information, followed by a stereoselective propagation event to control both tacticity and enantioselectivity. Using this method, we accessed both enantiomers of an isotactic polymer from a single enantiomer of monomer and identified a novel stereocomplex. These results represent a conceptual framework to expand stereoconvergent polymerization into additional monomers and mechanisms.