COORDINATION STRUCTURE OF THE ALUMINUM ATOMS OF POLY(METHYLALOXANE), POLY(ISOPROPOXYLALOXANE) AND POLY[(ACYLOXY)ALOXANE]

Poly(methylaloxane) (1), prepared by hydrolytic polymerization of trimethyl-aluminium (TMA), was reacted with isopropanol (IP) to obtain poly(isopropoxylaloxane) (2). This was further reacted with propionic acid (PA) to prepare poly[(propionyloxy) aloxanel (3), with various ratios of PA ligands. By gasmetry of the methane produced in the reaction, as well as by the 1H NMR spectroscopy of the products, both 1 and 2 were found to contain less reactive terminal A1Me and AlOH groups. For 3, the unit structure and molecular weight were controlled by the PA/TMA ratio reacted. The 27A1 NMR spectra of these products revealed that the coordination states of the aluminium atoms are different, depending on the O/A1 atomic ratio in the products. In the case of 1, which has a low O/A1 ratio, the aluminium atoms are penta-coordinated, while in 2 and 3 hexa-coordination is involved. Based on these data the structures of poly(aloxanes) (1-3) are discussed. © 1990.