Polymer Bulletin

, Volume 75, Issue 3, pp 1253–1263 | Cite as

Use of samarium(III)–amino acid complexes as initiators of ring-opening polymerization of cyclic esters

  • Dimas A. Medina
  • Jesús M. Contreras
  • Francisco J. López-Carrasquero
  • Eduardo J. Cardozo
  • Ricardo R. Contreras
Original Paper


Poly(ε-caprolactone) (PCL) and poly(l-lactide) (PLA) were prepared by ring-opening polymerization (ROP) using samarium(III) acetate (SmAc3) and amino acid complexes of samarium(III) as initiators. The catalytic behavior of samarium(III) acetate and their respective amino acid complexes, Sm(2,2′-bipyridine)(Ln)3 (L1 = l-aspartic acid; L2 = l-glutamic acid and L3 = glycine), was studied. It could be observed that the amino acid structure and chemical bond type have great influence on the catalytic activity. Polymerization reaction temperature was 125 °C and the effect of time reaction on the conversion of monomers to polymers and the molecular weight were studied. The results indicate that the initiators induce the polymerization of ε-caprolactone (ε-CL) and l-lactide (l-LA). Polymers were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (1H-NMR) and size exclusion chromatography (SEC). Polyesters with average-number molar mass of 1.50 × 103 − 104 Da were obtained. Based on the 1H-NMR end group analysis of low molecular weight of polymers, a coordination–insertion mechanism is proposed for the polymerization of lactones. Kinetics study indicated a polymerization rate of first order with respect to monomer concentration. Differences in the rates of polymerization in the four initiators appeared to be governed by the different degrees of steric hindrance in the initiator structure and monomer.


Samarium(III) acetate Amino acid–samarium(III) complex Ring-opening polymerization ε-Caprolactone Poly(ε-caprolactone) l-Lactide Poly(l-lactide) 



The authors thank the Consejo de Desarrollo Científico, Humanístico, Tecnológico y de las Artes of the Universidad de Los Andes (CDCHTA-ULA) for financial support (Grants C-1752 and C-1744). The authors also wish to thank Lic. Freddy Rojas and Dr. María Luisa Arnal of Simón Bolívar University, for their help with the SEC experiments.


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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Dimas A. Medina
    • 1
  • Jesús M. Contreras
    • 1
  • Francisco J. López-Carrasquero
    • 1
  • Eduardo J. Cardozo
    • 2
  • Ricardo R. Contreras
    • 2
  1. 1.Grupo de Polímeros, Departamento de Química, Facultad de CienciasUniversidad de Los AndesMéridaVenezuela
  2. 2.Laboratorio de Organometálicos, Departamento de Química, Facultad de CienciasUniversidad de Los AndesMéridaVenezuela

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