Highly stereoelective polymerization of rac‐(D,L)‐lactide with a chiral schiff's base/aluminium alkoxide initiator

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Abstract
A chiral Schiff's base/aluminium alkoxide initiator bearing a ligand derived from R‐(+)‐1,1′‐binaphthyl‐2,2′‐diamine was synthesized and used for the stereoelective polymerization of rac‐(D,L)‐lactide. Rather high stereoelectivity is observed: a polymer with 88% enantiomeric enrichment in D units is obtained at 19% conversion. At high conversions a stereocomplex between D‐ and L‐enriched stereocopolymers is formed. The polymerization reaction shows living type features, and narrow molecular weight distributions (M̄w/M̄n = 1,05–1,30) are obtained up to very high conversions. This indicates that transesterification reactions do not occur significantly with this sterically hindered initiator.