Solvent effect in 1,3-butadiene polymerization by cyclopentadienyl titanium trichloride (CpTiCl3)/methylaluminoxane (MAO) and pentamethylcyclopentadienyl titanium trichloride (Cp*TiCl3)/MAO catalysts

Stereospecific cis-1,4 polymerization of 1,3 butadiene is carried out by using CpTiCl3/MAO and Cp*TiCl3/MAO catalysts in solvents (mesitylene, toluene, benzene, chlorobenzene, m-chlorobenzene, hexafluorobenzene) having different nucleophilicity. The influence of nucleophilicity of used solvent on activity and selectivity of the two considered catalytic systems is evaluated. Catalyst activity is strongly affected by used solvent, while polymer microstructure remains almost unchanged. The formation of a labile specie anti-η3-π-butenyl-Ti coordinated to solvent molecule, able to increase the rate of polymerization reaction, is hypothesized. The effect of two different external electron donors, N(C2H5)3 and P(C6H5)3, in the polymerization environment on activity and selectivity of the two considered catalytic systems is also investigated. Both N(C2H5)3 and P(C6H5)3 induce a sweeping decrease of catalyst activity, but do not cause changes in polymer microstructures.