Enhancing Control and Speed in Anionic Ring-Opening Polymerization: A Continuous-Flow Ap-proach for Rapid, Well-Defined Polymers in Milliseconds

Anionic ring-opening polymerization (ROP) of epoxides, cyclic esters, and cyclic carbonates with strong bases such as potassium tert-butoxide (KOtBu) or potassium bis(trimethylsilyl)amide (KHMDS) is typically performed as batch reaction, leading to broad dispersity and poor control over the molecular weight mainly because of insufficient initiator efficiency and transesterifica-tion reactions. In this talk, I will present our work under the creative contribution of Jim Hedrick that led to com-bining a sterically hindered strong base such as KOtBu or KHMDS with a primary alcohol and us-ing a continuous-flow apparatus, affording control and reliability over the ROP and, remarkably, enabled the controlled polymerization of traditionally low-activity monomers such as δ-valerolactone and ε-caprolactone in milliseconds. These reactions exhibit characteristics capa-ble of producing narrow dispersity with predictable molecular weights and can rapidly generate well-defined block copolymers at residence times below 0.1 s. With reaction rates that are orders of magnitude higher than the fastest rates reported for urea anions, these reaction conditions offer great potential to expand the breadth of materials accessible.