Influence of the nature of the ligand on the microstructure of poly d,l-lactides prepared with organoaluminum initiators

The polymerization of d,l-lactide with organoaluminum initiators bearing two different ligands, acetylacetone (1) and achiral Schiff’s base (2), has been studied. The microstructure of the obtained polymers analyzed by high resolution 13C NMR (125 MHz) is strongly influenced by the nature of the ligand. Al(acac)3 (1) leads to stereocopolymers having random repartition of configurational units while polylactides prepared with aluminum methoxide derivatives bearing as ligand Schiff’s base (2) present some degree of stereoregularity with preferential formation of isotactic sequences. Variation of the ligand linked to the initiator appears as one of the best tools for the moulding of the microstructure of obtained polylactides.