Theoretical investigation of the molecular structure of aluminium triisopropoxide and its complexes in ring-opening polymerization

Vincent Parenté*, Jean Luc Brédas, Philippe Dubois, Nathalie Ropson, Robert Jérôme

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

We present a theoretical study on aluminium triisopropoxide (Al(O1Pr)3) using both empirical (Molecular Mechanics, MM, with Dreiding II force field) and quantum-chemical (Austin Model 1, AM1, semiempirical Hartree-Fock) techniques. We determine the most stable geometries for both the tetramer and trimer of aluminium triisopropoxide as well as the thermodynamic characteristics of the equilibrium existing between these two aggregated structures. The theoretical results are compared to experimental data from X-ray diffraction and 27AI NMR measurements. For the tetramer, it appears that the optimal equilibrium geometries are in good agreement with the experimental X-ray diffraction geometry; another geometry is also obtained with both theoretical approaches, which is slightly less stable but of higher symmetry. On the basis of the most stable configurations for the tetramer and trimer aggregates, the variation of free enthalpy (ΔG) between the two aggregated structures has been estimated. The evolution of the theoretical ΔG values indicates a displacement of equilibrium towards the trimer species with temperature, in good agreement with experimental 1H and 27AI NMR data. Moreover, the AM1 heats of formation show a gain of 33.9 kcal/mol due to the aggregation of four Al(O1Pr)3 instead of three, and thus a better stability of the tetramer. The molecular geometries being well described by the theoretical methods used in this study, we also present a model for the ring-opening polymerization complexes of ε-caprolactone and lactides.

Original languageEnglish (US)
Pages (from-to)525-546
Number of pages22
JournalMacromolecular Theory and Simulations
Volume5
Issue number3
StatePublished - May 1996
Externally publishedYes

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Polymers and Plastics
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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