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 epsilon-caprolactone (epsilon-CL) and copolymerization of epsilon-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 epsilon-CL with BPA as catalysts; the highest molar mass of PCL is 4.35 x 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 epsilon-CL catalyzed by BPA. More interestingly, ppm level of BPA is sufficient to catalyze controlled ROP of epsilon-CL.