화학공학소재연구정보센터
Macromolecules, Vol.41, No.13, 4688-4693, 2008
Dual catalytic system for combination of chain and step polymerizations: Ring-opening polymerization of epsilon-caprolactone and successive dehydration polycondensation with dicarboxylic acid using the same catalyst
We demonstrate a new system for the combination of chain and step polymerizations in which scandium trifluoromethanesulfon ate [Sc(OTf)(3)] catalyzes both polymerization modes. Ring-opening polymerization of E-caprolactone initiated from a diol was carried out in acetonitrile at 45 degrees C (M-n =1.2 x 10(3)-3.6 x 103, M-w/M-n = 1.3). After removing acetonitrile under reduced pressure, bulk polycondensation with methylsuccinic acid was performed at 100 degrees C for 15 h to give the polyester in an excellent yield (92-94%): M-n and M-w/M-n were respectively 1.4 x 104 and 1.9. To check whether transesterification occurred or not during. the two polymerizations, C-13 NMR measurement was carried out in CDCl3. Suppressed transesterification was also supported from reductive cleavage of polyester containing disulfide linkage synthesized using ring-opening copolymerization of c-caprolactone and successive polycondensation with 3,3'-dithiopropionic acid. Reversibly, chemoselective polycondensation of dicarboxylic acid containing a hydroxyl group and a diol and subsequent ring-opening copolymerization initiated from the pendent hydroxyl groups were also demonstrated using Sc(OTf)(3) as the dual catalyst.