Polymer Bulletin

, Volume 75, Issue 11, pp 5179–5195 | Cite as

Kinetics, mechanisms and polymer property studies of ring-opening polymerization of ɛ-caprolactone and lactides initiated by (benzimidazolylmethyl)amino Zn(II) alkoxides

  • Ekemini D. Akpan
  • Bernard Omondi
  • Stephen O. Ojwach
Original Paper


The reactions of substituted (benzimidazolylmethyl)amines ligands (L1–L3) with ZnEt2 in the presence of either BnOH or t-BuOH afforded the corresponding Zn(II) metal alkoxides [Zn(L1)(OBn)]2 (1), [(Zn(L2)(OBn)]2 (2), [Zn(L3)(OBn)]2 (3), [Zn(L2)(t-BuO)]2 (4), respectively. Complexes 14 formed effective initiators in the ring-opening polymerization (ROP) reactions of ɛ-caprolactone (ɛ-CL), D,L-lactide (D,L-LA) and L-lactide (L-LA). The ROP reactions followed pseudo-first-order kinetics with respect to monomer. Moderate molecular weight polymers of 10,650 g mol−1 exhibiting relatively narrow molecular weight distributions (1.16–1.54) were obtained. Predominantly crystalline isotactic poly(L-LA) and heterotactic poly(D,L-LA) were produced, respectively. Thermal analyses of PLA also supported the formation of isotactic poly(L-LA) with decomposition temperature of 298 °C.


Zinc alkoxides Polymerization Cyclic esters 



The authors would like to thank University of KwaZulu-Natal and National Research Foundation (NRF-South Africa) for financial support.

Supplementary material

289_2018_2321_MOESM1_ESM.docx (664 kb)
Supporting Information contains typical synthetic methods for the ligands and spectroscopic data, selected NMR and mass spectra of some complexes, kinetic plots and mass spectrum of polymers obtained. 1 (DOCX 664 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Ekemini D. Akpan
    • 1
  • Bernard Omondi
    • 1
  • Stephen O. Ojwach
    • 2
  1. 1.School of Chemistry and Physics, Westville CampusUniversity of KwaZulu-NatalDurbanSouth Africa
  2. 2.School of Chemistry and Physics, Pietermaritzburg CampusUniversity of KwaZulu-NatalScottsvilleSouth Africa

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