Non-symmetrical aluminium salen complexes: Synthesis and their reactivity with cyclic ester

- A number of Non-Symmetrical Aluminium Salen complexes were synthesized.
- These complexes were active in lactide and caprolactone polymerization.
- First-ordered kinetics with respect to lactide and caprolactone were observed.

Non-symmetrical aluminium salen complexes that contained different substituents were designed and synthesized. All the ligands and their complexes were characterized by 1H, 13C NMR and elemental analysis. These complexes can be used as catalysts to produce polylactide and poly-ε-caprolactone. All polymerizations were living and molar mass distributions were narrow. The Mn(obsd) of the isolated polymers were in good agreement with Mn(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 ε-caprolactone monomers.

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