Synthesis of block and end-functionalized polyesters by triflimide-catalyzed ring-opening polymerization of ε-caprolactone, 1,5-dioxepan-2-one, and rac-lactide

The ring-opening polymerization (ROP) of cyclic esters, such as epsilon-caprolactone, 1,5-dioxepan-2-one, and racemic lactide using the combination of 3-phenyl-1-propanol as the initiator and triflimide (HNTf2) as the catalyst at room temperature with the [monomer]0/[initiator]0 ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(epsilon-caprolactone) (PCL), poly(1,5-dioxepan-2-one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an 1H NMR analysis (PCL, Mn,NMR=5380; PDXO, Mn,NMR=5820; PLA, Mn,NMR=6490) showed good agreement with the calculated values. The 1H NMR and matrix-assisted laser desorption ionization time-of-flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf2-catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6-azido-1-hexanol, N-(2-hydroxyethyl)maleimide, 5-hexen-1-ol, and 2-hydroxyethyl methacrylate, successfully produced end-functionalized polyesters. In addition, poly(ethylene glycol)-block-polyester, poly(-valerolactone)-block-poly(epsilon-caprolactone), and poly(epsilon-caprolactone)-block-polylactide were synthesized using the HNTf2-catalyzed ROP. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 24552463