Controlled Ring-Opening Homo-and Copolymerization of E-Caprolactone and D, L-Lactide by Iminophenolate Aluminum Complexes: An Efficient Approach toward Well-Defined Macromonomers

The aluminum complexes containing two iminophenolate ligands of the type (p-XC6H4NCHC6H4O-o)(2)AlR' (R=Me (3, 4) or R=O(CH2)(4)OCH=CH2 (5, 6), X=H (3, 5), F(4, 6)) were synthesized and characterized by H-1, C-13 NMR spectroscopy, and X-ray crystallography. The reaction of AlMe3 with two equivalents of substituted iminophenols gave five-coordinated {ONR}(2)AlMe (3, 4) complexes. Subsequent reaction of these methyl complexes with unsaturated alcohol, HO(CH2)(4)OCH=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 -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 (F-n > 80%) in a broad range of molecular weights (M-n = 4000-30,000 g mol(-1)) with relatively narrow MWD (M-w/M-n = 1.1-1.5). (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1237-1250