Versatile Copolymerization of Glycolide and rac-Lactide by Dimethyl(salicylaldiminato) aluminum Compounds

The dimethylaluminum compounds Al(CH3)2[(O-2-{(C6F5)N═CH}-4,6-R2C6H2)], R = H (1) or cumyl (2), were synthesized and tested as initiators in the homo- and copolymerization of rac-lactide and glycolide. These complexes resulted active for the production of PLGA copolymers with variable microstructure. All the copolymers were fully characterized by NMR, GPC, and DSC analysis. The copolymerization reactions were performed in bulk and in solution, by varying comonomers ratio, monomer/catalyst feed ratio, temperature, reaction time, and solvent. Interestingly, by changing the reaction conditions, copolymers from random, to blocky, to diblock were obtained, demonstrating the effectiveness and versatility of such systems in modulating the copolymers microstructure and the related thermal properties.