Aluminum Salen Complexes Modified with Unsaturated Alcohol: Synthesis, Characterization, and Their Activity towards Ring-Opening Polymerization of ε-Caprolactone and <i>D</i>,<i>L</i>-Lactide

Abstract

A highly efficient one-step approach to the macromonomer synthesis using modified aluminum complexes as catalysts of ring-opening polymerization (ROP) of ε-caprolactone and D,L-lactide was developed. The syntheses, structures, and catalytic activities of a wide range of aluminum salen complexes, 3a-c, functionalized with unsaturated alcohol (HO(CH2)4OCH=CH2) are reported. X-Ray diffraction studies revealed a tetragonal pyramidal structure for 3c. Among the complexes 3a-c, the highest activity in bulk ROP of ε-caprolactone and D,L-lactide was displayed by 3b, affording polyesters with controlled molecular weights at low monomer to initiator ratios (Mn up to 15,000 g mol−1), relatively high polydispersities (Ð~1.8) and high number-average functionalities (Fn up to 85%).

Keywords

• salen
• imine ligands
• aluminum complex
• aluminum alkoxide
• NMR spectroscopy
• X-ray diffraction analysis