Titanium-salen complexes as initiators for the ring opening polymerisation of rac-lactide |
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Authors: | Gregson Charlotte K A Blackmore Ian J Gibson Vernon C Long Nicholas J Marshall Edward L White Andrew J P |
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Affiliation: | Imperial College London, Department of Chemistry, South Kensington Campus, London, UK SW7 2AZ. |
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Abstract: | A family of bis(iso-propoxide) titanium(IV) complexes supported by tetradentate Schiff base (salen) ligands has been synthesised and characterised, including a structural determination of N,N'-bis(6'-methylenimino-2',4'-di-tert-butylphenoxy)cyclohexyl-(1R,2R)-diamino titanium(IV) bis(iso-propoxide). Their suitability for initiating the ring-opening polymerisation of rac-lactide has been investigated. Polymerisation activities are shown to correlate with the electronic properties of the substituents within the salen ligand. In contrast to aluminium-salen initiators, electron-withdrawing substituents on the Schiff base ligand have a detrimental influence upon polymerisation activities, whereas the use of electron-donating alkoxy-functionalized ligands has allowed the highest recorded activity to date for a titanium-based initiator. |
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