Preparation and characterization of aluminum alkoxides and their application to ring-opening polymerization of epsilon-caprolactones

Abstract

The reaction of 2-methoxybenzyl alcohol with one molar equiv of R2AlX in diethyl ether at 0 degreesC gives [(2-MeOC6H4CH2-mu -O)AIRX](2) (1: R = Et, X = Cl, 2: R = X = Et). In addition, 2,4-di-tert-butylphenol reacts with (Bu3Al)-Bu-1 affording a four-coordinated aluminum compound [(mu -2,4-Bu-t(2)-C6H4O)Al(Bu-i)(2)](2) (4). Single crystal X-ray structure analysis of 4 shows a C-2h-symmetry with a planar Al2O2 core. Ring-opening polymerization (ROP) of caprolactones initiated by 1, 4 and [(mu -OCH2C6H4OMe)Al(Bu-i)(2)](2) (3) is performed and polyesters with narrow molecular weight distributions were obtained from the "living" ROP of caprolactones. H-1 NMR spectroscopic studies of PCL reveal that the initiator of 1 and 3 is through the Al-OAr function, but the initiator of 4 is through the Al-Bu-i group.