Butadiene polymerization initiated by polynuclear Nd-Al bimetallic complex IV. Influence of different aluminium alkyls

Based on the polynuclear Nd-Al bimetallic complex, which can initiate diene polymerization alone, the effect of different aluminium alkyls on butadiene polymerization was examined in the presence of additional aluminium alkyls and the obtained results were compared with the conventional mixed rare earth catalytic system. The effect of different aluminium alkyls on the catalytic activity was found to vary with the amount of aluminium alkyls, at lower Al/Nd molar ratio, the activity decreased in the following order: AlMe₃, AlEt₃, HAlBu₂ⁱ> Al(C₈H₁₇)₃>AlBu₃ⁱ, and at higher Al/Nd molar ratio, the above order was reversed completely. The ability of chain transfer of aluminium alkyls decreased as follows: HAlBu₂ⁱ≥AlEt₃>AlBu₃ ⁱ>AlMe₃>Al(C₈H₁₇)₃. In accordance with the relationship between relative molecular mass and microstructure of polybutadiene, the effect of aluminium alkyls on the content of poly (cis-1, 4-butadiene) could be divided into three groups: (1) AlEt₃ and Al(C₈H₁₇)₃; (2) HAlBu₂ⁱ and AlBu₃ⁱ; (3) AlMe₃. The results are useful for deep-going understanding of the stereospecific polymerization initiated by rare earth.