| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1998: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Research Abstract |
Four non-bridged and five dimethylsilylene-bridged zirconocenedimethyls, i.e., bis(eta^5-cyclopentadienyl)dimethylzirconium(1), (eta^5-cyclopentadieny)(eta^5-fluorenyl)dimethylzirconium(2), bis(eta^5-indenyl)dimetliylzirconium(3), (eta^5-cyclopentadieny)(eta^5-pentamethylcyclo- pentadieny)dimethylzirconium(4), dimethylsilylenebis (eta^5-cyclopentadienyl)dimethy1zirconium(5), dimethylsilylene(eta^5-cyclopentadienyl)(eta^5-fluorenyl)dimethylzirconium(6), rac-dimethylsilylenebis(eta^5-cyclopentadienyl)dimethylzirconium(7), meso-dimethylsilylenebis(eta^5-cyclopentadienyl)dimethylzirconium(8) and dimethylsilylene(eta^5-cyclopentadienyl)(eta^5-indenyl)dimethylzirconium (9) were synthesized and used as a catalyst for methyl methacrylate polymerization combined with triphenylmethyltetrakis(pentafluorophenyl)borate or N,N-dimethylpyridinyltetrakis(pentafluorophenyl)borate in the presence of ZnEt_2 or Al(i-Bu)_3.
The catalyst activity strongly depended on the zirconocene compounds and decreased i
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n the following order ; 2> 1 > 7 > 5 > 9 > 3 >> 4, 6, 8 = 0. The polymerization proceeded in a living manner when 1 and 2 were used combined with ZnEt_2. The stereoregularity of the polymers obtained with the non-bridged zirconocenes were independent of the cyclopentadienyl ligands, and syndiotactic-rich polymers were formed by a chain-end controlled mechanism. The stereospecificity of the silylene-bridged zirconocenes were strongly depended on their symmetries. C_<2v>-symmetric 5 gave a syndiotactic-rich polymer similarly to the non-bridged zirconocenes, while C_2-symmetric 7 and C_1-symmetric 9 gave highly isotactic polymers by a enantiomorphic-site controlled mechamsm.
These catalyst systems are also active for polymerization of allyl methacrylate to give polymers with pendant allyl-ester groups. The stereoregularity of the polymers were the same with poly(methyl methacrylate), which could be controlled by the zirconocene compounds employed. Random copolymerization of allyl methacrylate and methyl methacrylate also proceeded to produce poly(methyl methacrylate) with pendant allyl-ester groups, of which content was easily controlled by the feed ratio. Less
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