| Research Abstract |
A SiO_2-supported (η^5-cyclopentadienyl) titanium trichloride was prepared and applied for copolymerization of ethylene and 1,3-butadiene using the mixture of triisobutylaluminum and triphenylmethyl tetralkis (pentafluorophenyl) borate as an activator. The system was found to give copolymers with selectivities of 80 % at 40 ℃ and more than 99 % at ℃. The butadiene contents, of which structure was trans-1,4-addition, was varied from 0.5 to 2.5 mol %. The trans-1,4-addition units in the copolymer were selectively oxidized with potassium permanganate, which produced α,ω-dicarboxypolyethylene. The polydispersity of the gegradation products, M_W/M_n = 2, indicated that the butadiene units were distributed randomly in the main chain. A series of zirconocene compounds activated by the mixture of triisobutylaluminum and triphenylmethyl tetralkis (pentafluorophenyl) borate was then applied for the copolymerization of ethylene and 1,3-butadiene at 40℃. The polymerization activity strongly depend
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ed on the structure of zirconocene compounds : bridged and non-bridged C_<2v>-symmetric zirconocenes did not give polymers, whereas C_2-symmetric and C_3-symmetric bridged zirconocenes produced copolymers with more than 90 % selectivity. Among the zirconocenes used, diphenymethyl(η^5-cyclopentadienyl(η^5-cyclopentadienyl)zirconium dichloride (I) showed the highest activity and gave the copolymer with the highest butadiene content. The copolymer contained ca. 8 mol % of frans-1,4-addition unit and ca. 20 mol % of cyclopentane unit., that is, the structure of the copolymer was very similar to that of ethylene-butadiene-cyclopentene copolymer. The butadiene contents of the copolymer showed a good relation with the activity and decreased in the following order : I > other C_5-symmetric zirconocenes > C_2-symmetric zirconocenes. When the copolymerization was condacted with I at O ℃, the copolymer was selectively obtained. Copolymerization of ethylene and 1,3-butadiene was also conducted with cobalt dichloride activated by methylaluminoxane. Although the copolymerization did not proceed, cobalt dichloride-methylauminoxane was found to effective for cis-specific living polymerization of 1,3-butadiene. Less
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