Controlled ring‐opening homo‐ and copolymerization of ɛ‐caprolactone and d,l‐lactide by iminophenolate aluminum complexes: An efficient approach toward well‐defined macromonomers

Abstract

ABSTRACTThe aluminum complexes containing two iminophenolate ligands of the type (p‐XC6H4NCHC6H4O‐o)2AlR' (R′=Me (3, 4) or R′=O(CH2)4OCH=CH2 (5, 6), X=H (3, 5), F(4, 6)) were synthesized and characterized by 1H, 13C NMR spectroscopy, and X‐ray crystallography. The reaction of AlMe3 with two equivalents of substituted iminophenols gave five‐coordinated {ONR}2AlMe (3, 4) complexes. Subsequent reaction of these methyl complexes with unsaturated alcohol, HO(CH2)4OCH=CH2, resulted in target compounds 5 and 6 in a good yield. It was shown that the complexes (3‐6) are monomeric in solution (NMR) and in solid state (X‐ray analysis). The catalytic activity of the complexes 5 and 6 towards ring‐opening polymerization (ROP) of ɛ‐caprolactone and d,l‐lactide was assessed. Complex 5 showed higher activity as compared with 6, while both of these catalysts induced controlled homo‐ and copolymerization to afford the macromonomers with high content of vinyl ether end groups (Fn > 80%) in a broad range of molecular weights (Mn = 4000–30,000 g mol−1) with relatively narrow MWD (Mw/Mn = 1.1–1.5). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1237–1250