Group 4 Metal Complexes of Phenylene–Salalen Ligands in rac-Lactide Polymerization Giving High Molecular Weight Stereoblock Poly(lactic acid)

Ayellet Stopper, Tomer Rosen, Vincenzo Venditto, Israel Goldberg, Moshe Kol

Research output: Contribution to journalArticlepeer-review

Abstract

Phenylene–salalens—sequential tetradentate dianionic {ONNO}-type ligands that include an ortho-phenylene group bridging between an imine and amine internal donors bound to phenol arms with a broad variety of substitution patterns are described. Zirconium and hafnium complexes of the type [{ONNO}M(O-tBu)2] were formed as single diastereomers, which, according to crystallographic structures, featured the fac(around the amine)-mer(around the imine) wrapping mode. The reactivity and stereoselectivity in rac-lactide (rac-LA) polymerizations were found to depend on the substitution pattern: complexes featuring small groups on the imine-side phenol and bulky groups on the amine-side phenol exhibited the favorable combination of high activity and high isoselectivity (Pm≤0.91). Isotactic stereoblock copolymers of high molecular weights were prepared. The polymers crystallized in the stereocomplex phase according to thermal (differential scanning calorimetry) and crystallographic analysis.

Original languageEnglish
Pages (from-to)11540-11548
Number of pages9
JournalChemistry - A European Journal
Volume23
Issue number48
DOIs
StatePublished - 25 Aug 2017

Keywords

  • hafnium
  • isotacticity
  • lactide
  • poly(lactic acid)
  • zirconium

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