Phosphorus pentoxide as a cost-effective, metal-free catalyst for ring opening polymerization of epsilon-caprolactone

The ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) using phosphorus pentoxide (P2O5) as a metal-free catalyst and isopropanol (iPrOH) as initiator resulted in the preparation of poly(epsilon-caprolactone) with narrow weight distribution. NMR spectroscopy analyses of the prepared PCL indicated the presence of the initiator residue at the end of the polymer chain, implying the occurrence of the epsilon-CL-catalysis ROP through a monomer activation mechanism. Kinetic experiments confirmed the controlled/living nature of epsilon-CL ring-opening catalyzed by phosphorus pentoxide. The commercial availability of phosphorus pentoxide and its easy-handling provide additional opportunities for polymer synthesis and nanocomposite manufacturing.