Ring‐Opening Polymerization of Cyclic Monomers with Aluminum Triflate

Abstract

AbstractA green method for the controlled synthesis of aliphatic polymers is presented. The ring‐opening polymerizations of cyclic monomers including several lactones, such as caprolactone (CL) or pentadecalactone (PDL), and cyclic anhydride monomers, such as succinic anhydride (SUC) and tetrahydrofuran (THF), catalyzed by a series of metal triflates (trifluoromethanesulfonate) were studied. Aluminum triflate was found to be an advantageous candidate to catalyze the ring‐opening polymerization of cyclic monomers. The details of the ring‐opening polymerization of CL catalyzed by aluminum triflate were studied. The maximum number average molecular weight (Mn), polydispersity (Mw/Mn) and yield of the obtained poly(‐caprolactone) (PCL) at 60 °C for 6 hours were 18,400, 1.94 and 89 wt%, respectively. Those of poly(pentadecalactone) (PPDL) at 100 °C for 6 hours were 12,400, 2.24 and 49 wt%, respectively. The Mn, Mw/Mn and yield of the obtained poly(butylene succinate) (PBS) from SUC and THF at 100 °C for 48 hours were 4,900, 2.03 and 84 wt%, respectively. Furthermore, the mechanism of the polymerization was discussed based on the relationship between the conversion of CL and time. The molecular weight buildup of PCL was linear with a conversion in 50 min before the conversion reached 100 % and with Mw/Mn stabilized at about 1.5. The Mw/Mn of PCL then gradually increased. From these data, a living polymerization with a small transesterification was suggested from the PCL polymerization by aluminum triflate.