Isoselective Ring-Opening Polymerization to Access High-Performance Poly(α-Substituted-β-Propiolactone)s

Poly(α-substituted-β-propiolactone), P(αRPL), is attractive since it is closely related in structure to the biodegradable natural polyhydroxyalkanoates (PHAs). However, the chemical synthesis of isotactic P(αRPL) via ring-opening polymerization has yet to be explored. Herein, we exploited a robust salalen yttrium complex (Y2) as the catalyst to successfully prepare highly isotactic P(αRPL) with P_m > 0.95. These P(αRPL) products exhibited tacticity-dependent thermal and mechanical properties. Remarkably, the highly isotactic P(BPL) containing a benzyl side chain showcased a high melting transition temperature (T_m) of 165 °C. The highly isotactic P(n-BuPL) containing alkyl side chain served as a strong and ductile material comparable to the commercial high-density polyolefins. More importantly, these P(αRPL) products could undergo clean depolymerization to their starting material, α-substituted acrylic acids, offering a closed-loop recycling pathway. This synthetic system allowed access to isotactic P(αRPL), establishing a powerful platform for the discovery of sustainable plastics.