Stereoselective ring-opening polymerization of racemic lactide using aluminum-achiral ligand complexes: Exploration of a chain-end control mechanism

Stereoselective polymerization of racemic lactide (rac-LA) was examined using Al-achiral ligand complexes. By introduction of substituents in aromatic rings of Schiff base ligands, a higher selectivity was obtained without any chiral auxiliaries in the catalyst via a chain-end control mechanism. The Tm values (Tm 170-192 °C) were comparable to or higher than that of homochiral polymer, poly(l-LA) (Tm 162 °C), and a thermally more stable polylactide than poly(l-LA) was prepared from rac-LA. Copyright © 2002 American Chemical Society.