Efficient ring-opening polymerization of epsilon-caprolactone catalyzed by iron(III) chloride under mild reaction conditions

As a biodegradable polyester, the commercialized synthesis protocol of poly(ε-caprolactone) (PCL) under mild conditions is of great significance and attractive. Herein, the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) using FeCl 3 catalyst and benzyl alcohol (BnOH) as the initiator was developed. FeCl 3 has been proved to be an efficient catalyst for the ROP of ε-CL under mild conditions. The conversion of ε-CL to PCL was 98.8% at 60 °C within 4 h, with number-average molecular weight ( M n) and dispersity (PDI) of 1.65 × 10 4  g/mol and 1.28, respectively. Moreover, a coordination-insertion ring-opening polymerization mechanism mediated by FeCl 3 was proposed. Overall, this work is expected to provide a feasible industrial method for the preparation of PCL from the direct aerobic oxidation of cyclohexanone.