Health & Environmental Research Online (HERO)


Print Feedback Export to File
5636071 
Journal Article 
Polymerizations of butadiene, isoprene, and 2,3-dimethylbutadiene by Cd(OCOCCl3)(3)-(i-Bu)(3)Al-Et2AlCl and the cis polymerization mechanism for dienes 
Kobayashi, E; Kaita, S; Aoshima, S; Furukawa, J 
1998 
Yes 
Journal of Polymer Science. Part A, Polymer Chemistry
ISSN: 0887-624X
EISSN: 1099-0518 
JOHN WILEY & SONS INC 
NEW YORK 
36 
13 
2283-2290 
WOS:000075690400015 
Homopolymerizations of butadiene (BD), isoprene (IP), and 2,3-dimethyl-butadiene (DMBD) were carried out by a Gd(OCOCCl3)(3)-based catalyst, to investigate the effects of the energy levels of the monomers or the sterical factor of the methyl substituents on the polymerizability and the cis-selectivity of the monomers. The order of the polymerizability at 50 degrees C was as follows: ED (4.5 kg of polymer/(mol of Gd h)) similar to IP (4.8) > DMBD (0.6). On the other hand, the cis-selectivity of the polymers was as follows: ED (98%) > IP (94%) much greater than DMBD (35%). These results suggest that the terminal ED and IP units are controlled by the cis configuration by the coordination between the penultimate cis-vinylene unit and the catalyst metal, whereas the penultimate DMBD unit unfavorably controls the terminal DMBD unit to the cis-1,4 configuration through the back-biting coordination with difficulty by two methyl substituents compared with the penultimate ED and TP units. The validity of the back-biting coordination was examined by MO calculation with sigma-allylnickel complexes. According to the formation energy with respect to the BD-BD diad, the cis-cis form is somewhat preferable to the trans-cis form through the coordination of the penultimate ED unit by Delta E = 0.028 au (ca. 17.6 kcal/mol). (C) 1998 John Wiley & Sons, Inc. 
Ziegler type catalyst; Gd(OCOCCl3)(3) catalyst; polymerization of dienes; cis-1,4 polymerization mechanism; back-biting coordination; MO calculation of sigma-allylnickel complex