Random polymer formation in copolymerization of ʟ-lactide and ε-caprolactone initiated by aluminum pyridine-bis(phenolate): a quantum chemical study

The ring-opening homo- and copolymerization of ε-caprolactone (CL) and ʟ-lactide (LA) using an aluminum complex with 2,2'-di-tert-butyl-6,6'-(pyridine-2,6-diyl)diphenolate and methoxide ligands as initiator was investigated by means of density functional theory (DFT) calculations. The initial stages of CL and LA polymerization as well as the first propagation stages were analyzed in detail and the activation barriers of the reactions were compared. The lowest activation barriers were found for the alternate addition of monomers, which resulted in the formation of a random copolymer as a product.