Mononuclear zinc(II) Schiff base complexes as catalysts for the ring-opening polymerization of lactide

Martin Fuchs, Sebastian Schmitz, Pascal M. Schaefer, Tim Secker, Angela Metz, Agnieszka N. Ksiazkiewicz, Andrij Pich, Paul Koegerler, Kirill Yu Monakhov, Sonja Herres-Pawlis*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Materials combining bio-based resource and degradability aspects such as polylactide (PLA) can represent a sustainable alternative to commercially used oil-based plastics. With tin octanoate (Sn(Oct)(2)) as the catalyst of choice for industrial scale PLA production, traces of the toxic heavy metal can be released into the environment, rendering PLA unsuitable for specific applications. Herein we present four new homoleptic zinc Schiff base complexes that offer facile synthesis and can be handled under aerobic conditions. These robust, tetra-coordinated complexes have been tested as catalysts for the ring-opening polymerization (ROP) of lactide and are well suited under industrially relevant conditions. In situ Raman spectroscopy has been used to determine the apparent reaction rate constant (k(app)) for all complexes at 150 degrees C in bulk. For the fastest complex a k(p) of 3.66 +/- 0.14 x 10(-2) L mol(-1) s(-1) was additionally determined. For this catalyst, 71% conversion and a number-averaged molar mass of above 90000 g mol(-1) has been reached within less than 30 min at a monomer-to-initiator ratio ([M]/[I]) of 1000:1. The good polydispersity (D = 1.7) indicates a controllable ROP via the coordination-insertion mechanism (CIM).

Original languageEnglish
Article number109302
Number of pages7
JournalEuropean Polymer Journal
Publication statusPublished - 5 Jan 2020


  • Ring opening polymerization
  • Lactide polymerization
  • Schiff base ligands
  • Zinc catalysts

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