Stereoselective Polymerization of Conjugated Dienes and Styrene−Butadiene Copolymerization Promoted by Octahedral Titanium Catalyst

The ability of the dichloro{1,4-dithiabutanediyl-2,2‘-bis(4,6-di-tert-butylphenoxy)}titanium complex (1) to catalyze homopolymerization of conjugated dienes and copolymerization of butadiene with styrene is reported. After proper activation with methylalumoxane, 1 resulted active in the trans-1,4 selective polymerization of butadiene and isoprene with good activity. The molecular weight distributions of the polymers are monomodal with the polydispersity indexes, consistent with a single site behavior of the catalyst. Isotactic polystyrene-co-trans-1,4-polybutadiene with an unprecedented architecture, covering a wide range of compositions (x S = 0.15−0.97), were also obtained. The chemo- and stereoselectivity of butadiene insertion and the isospecific styrene polymerization of the title catalyst are retained when the two monomers are copolymerized. The molecular weight distributions are consistent with the material being copolymeric in nature. The reactivity ratios values and the microstructure analysis (by means of 13C NMR) indicate a random distribution of the two monomers in the polymer chain.