Supporting Effects of Methylaluminoxane on the Living Polymerization of Propylene with a Chelating (Diamide)dimethyltitanium Complex

Summary: Modified methylaluminoxane (MMAO), from which free AlMe 3 and Al( i Bu) 3 were reduced to ca. 0.1 mol‐%, was supported on metal oxides, such as anhydrous silica gel, alumina, or magnesia; the metal oxide‐supported MMAO prepared were used as cocatalysts for propylene polymerization combined with a chelating (diamide)dimethyltitanium complex. The systems conducted living polymerization of propylene at 0 °C regardless of the support for MMAO. The propagation rate constants ( k p ) of these systems and the molecular weight distribution ( $\overline M _{\rm w} {\rm /}\overline M _{\rm n}$ ) of the produced polymer depended on the metal oxide employed. The XPS analysis of the supported MMAOs suggested that the k p value increased with the Lewis acidity of MMAO on the support and the broadening $\overline M _{\rm w} {\rm /}\overline M _{\rm n}$ was ascribed to the distribution of k p caused by the heterogeneity of the supported cocatalyst.Plots of \overline M _{\rm n} and \overline M _{\rm w} {\rm /}\overline M _{\rm n} against polymerization time in propylene polymerization with [ArN(CH 2 ) 3 NAr]TiMe 2 : MMAO/SiO 2 system, \overline M _{\rm n} (•), \overline M _{\rm w} {\rm /}\overline M _{\rm n} (○); MMAO/Al 2 O 3 system, \overline M _{\rm n} (▴), \overline M _{\rm w} {\rm /}\overline M _{\rm n} (▵); MMAO/MgO system, \overline M _{\rm n} (▪), \overline M _{\rm w} {\rm /}\overline M _{\rm n} (□); corresponding homogeneous system, \overline M _{\rm n} (▾), \overline M _{\rm w} {\rm /}\overline M _{\rm n} (▿).