Electron rich (salen)AlCl catalysts for lactide polymerisation: Investigation of the influence of regioisomers on the rate and initiation efficiency
| Autor: | Annabel Rae, Jennifer A. Garden, Anand J. Gaston, Zoe Greindl |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
chemistry.chemical_classification
Lactide Polymers and Plastics Organic Chemistry General Physics and Astronomy Epoxide Ether 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Medicinal chemistry 0104 chemical sciences Catalysis chemistry.chemical_compound chemistry Polymerization Tacticity Materials Chemistry Structural isomer 0210 nano-technology Lactone |
| Zdroj: | Rae, A, Gaston, A J, Greindl, Z & Garden, J A 2020, ' Electron rich (salen)AlCl catalysts for lactide polymerisation: Investigation of the influence of regioisomers on the rate and initiation efficiency ', European Polymer Journal, vol. 138, pp. 109917 . https://doi.org/10.1016/j.eurpolymj.2020.109917 |
| ISSN: | 0014-3057 |
| DOI: | 10.1016/j.eurpolymj.2020.109917 |
| Popis: | Aluminium-alkyl complexes are well known as initiators for lactide ring-opening polymerisation, yet aluminium-chloride complexes remain underexplored despite benefits such as ease of synthesis and improved air-stability. While aluminium-chloride complexes are typically poor initiators, recent studies have shown that electron rich amino-substituted (salen)AlCl complexes can efficiently initiate lactide polymerisation in the presence of an epoxide. Herein, we report eight ether-substituted complexes as efficient initiators for lactide polymerisation, where exchanging strongly electron-donating amino groups for weaker electron-donating methoxy substituents maintains efficient initiation and also improves the propagation rate by a factor of four. Investigation of ortho-, meta-, para- and meta’-methoxy-substituted regioisomers established that the ortho-substituted complex was twice as active as the other regioisomers. Kinetic and spectroscopic studies suggest that the initiation efficiency is influenced by the electronics (ortho and para > meta and meta’), with substituents closer to Al giving improved initiation (ortho > para and meta’ > meta). While electron-donating ortho-substituents often decrease catalyst activity in lactone polymerisation, here we show that ether groups can act as σ-electron-withdrawing groups and π-electron donors, to deliver improved propagation rates, initiation and tacticity control. |
| Databáze: | OpenAIRE |
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