Controlled ring-opening polymerization of cyclic esters with phosphoric acid as catalysts

( R )-(−)-1,1′-Binaphthyl-2,2′-diyl hydrogen phosphate (BPA) has been demonstrated as an efficient organocatalyst for controlled ring-opening homopolymerization of ε-caprolactone (ε-CL) and copolymerization of ε-CL with glycolide and lactide. High molar mass PCL with narrow molar mass distribution has also been synthesized from the bulk ring-opening polymerization (ROP) of ε-CL with BPA as catalysts; the highest molar mass of PCL is 4.35 × 10 4  g/mol with polydispersity index of 1.20. The successful synthesis of high molar mass PCL is attributed to the bifunctional activation mechanism for the ROP of ε-CL catalyzed by BPA. More interestingly, ppm level of BPA is sufficient to catalyze controlled ROP of ε-CL.