Living and Controlled Ring-Opening (co)Polymerization of PDL Catalyzed by <i>N</i> -Heterocyclic Olefin/Al(C ₆ F ₅ ) ₃ Lewis Pair

Controlling transesterification is a significant challenge in the ring-opening polymerization (ROP) of macrolactones, especially at elevated temperatures. We report an N -heterocyclic olefin/Al(C 6 F 5 ) 3 Lewis pair system for the living and controlled ROP of ω-pentadecalactone (PDL), yielding polyesters with a linear dependence of M n on the PDL feeding ratio ( M n up to 122.0 kg/mol). This system not only enables the homopolymerization of PDL but also the copolymerization of PDL with small-ring lactones producing either random or block copolyesters under identical reaction conditions. Single-feed copolymerization of PDL with small-ring lactones, δ-Valerolactone (VL) and ε-caprolactone (CL), results in random polymers, while sequential-feed copolymerization preserves block structures using a “PDL block first” approach. Furthermore, this random copolymerization strategy enables the preparation of polyesters with tunable melting temperatures ( T m ) and thermal stability. Overall, this work establishes a practical platform for the design of polyester-based materials with tailored properties.