Di-,Tri- and Tetrafunctional Poly(epsilon-caprolactone)s by Bi(OAc)_3-Catalyzed Ring-Opening Polymerizations of epsilon-Caprolactone

摘要

epsilon-Caprolactone was polymerized in bulk at 150degC with either tetra(ethylene glycol) (TEG),l,l,l-tris(hydroxymethyl)propane,or Pentaerythritol as initiator and bismuth(III) acetate Bi(OAc)_3 as catalyst.The reaction times needed for nearly quantitative conversion were determined.The polylactones isolated after precipitation were characterized by ~1H NMR spectroscopy and MALDI-TOF mass spectroscopy.Quantitative incorporation of the initiators were confirmed,so that polylactones having two,three,or four OH end groups were obtained.A coordination-insertion mechanism explaining these results is discussed.When used as catalyst for ring-opening polymerizations of lactones and lactides bismuth(III) carboxylates have three important advantages,particularly low toxicity,low transesterifi-cation activity ("backbiting degradation"),and no racemization when L-lactide is polymerized at temperatures up to 180degC.