Side-Group Recognition Promoting Self-Switchable Ring-Opening Polymerization to Access High-Performance (AB)nCm Block Copolyesters.

The synthesis of sequence-controlled block copolyesters from mixtures of both cyclic ester monomers remains challenging, as insufficient chemoselectivity leads to gradient or statistical copolymers rather than well-defined block structures. Herein we exploit CH-π interactions between a zirconium alkoxide initiator and the aryl side group of a lactone monomer to selectively enhance the coordination of asymmetric 3-phenyl-1,4-dioxane-2,5-diketone (PDD) over that of ε-caprolactone (CL) in a self-switchable ring-opening polymerization (ROP). This monomer side-group recognition promoted preferential binding makes the ROP of PDD kinetically favored over that of CL, thereby endowing the system with high chemoselectivity. As a result, PDD is consumed rapidly and nearly completely (98% conversion) before the polymerization autonomously switches to the ROP of CL, affording well-defined (AB)nCm-type diblock copolyesters. By supplying additional monomer mixtures sequentially during the polymerization, this approach can be further extended to sequence-controlled ((AB)nCm)z-type multiblock copolyesters. The thermal and mechanical analyses reveal that both block length ratios and chain architecture govern material performance. Remarkably, the diblock PPDD-b-PCL exhibited a tensile strength of 47.2 ± 2.5 MPa and an elongation at break of 942.0 ± 45.0%, making it a strong and ductile material comparable to commercial isotactic polypropylene. This work establishes a side-group recognition approach for self-switchable polymerization, establishing a powerful platform for the precision synthesis of sustainable plastics.