e-Caprolactone / ZnCl2 complex formation: characterization and ring-opening polymerization mechanism

ABRAHAM,G.A.; GALLARDO,A.; LOZANO,A.; SAN ROMAN,J

JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY

John Wiley & Sons, Inc.

Lugar: New York, USA; Año: 2000 vol. 38 p. 1355 - 1365

0887-624X

e-Caprolactone (e-CL) has been mixed with ZnCl2 at different mole ratio. The resulting complex was characterized through 1H and 13C NMR spectroscopy in bulk and in solutions, differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and optical microscopy. Ring-opening polymerization of e-caprolactone [M] using ZnCl2 as initiator [I] at different monomer/initiator ratio have been successfully performed in xylene. The molecular weight of poly(e-caprolactone) (PCL) as measured by gel permeation chromatografy (GPC) was found to depend linearly on the [M]/[I] ratio. Theoretical calculations were carried out in order to understand the geometry of the complex and the operating ring-opening mechanism. Both experimental and computational results and the presence of methylene-chloride endgroup, confirmed by NMR, are in agreement with a coordination-insertion mechanism for the ring-opening polymerization proposed in this article.