Non-symmetrical aluminium salen complexes that contained different substituents were designed and synthesized. All the ligands and their complexes were characterized by H-1, C-13 NMR and elemental analysis. These complexes can be used as catalysts to produce polylactide and poly-epsilon-caprolactone. All polymerizations were living and molar mass distributions were narrow. The M-n(obsd) of the isolated polymers were in good agreement with M-n(calcd). The polymerization rate of electrophilic substituted complex was higher than the non-electrophilic substituted analogies. The bulky substituents with more steric hindrance of the complexes had relatively lower activity. Kinetic studies showed that the polymerizations were both first-ordered with respect to lactide and epsilon-caprolactone monomers. (C) 2015 Elsevier Ltd. All rights reserved.