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Polymerization of 1,7-octadiene was conducted with isospecific rac-dimethylsilylenebis(indenyl)zirconium dichloride (1), syndiospecific diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride (2) and aspecific bis(cyclopentadienyl)zirconium dichloride (3) metallocene catalysts combined with methylaluminoxane. The microstructure of the poly(1,7-octadiene)s produced was characterized by means of 1H NMR, 13C NMR and DEPT (distortionless enhancement by polarization transfer) spectroscopy. A portion of monomeric units in poly(1,7-octadiene)s is saturated as a result of cycloaddition. The fraction of the saturated units (cyclization selectivity) decreases in the following order: 1 > 3 > 2. The effect of polymerization temperature was studied, and the cyclization selectivity was found to decrease with lowering the polymerization temperature. The monomer concentration affects the microstructure of poly(1,7-octadiene), and the cyclization selectivity is drastically decreased with increasing monomer concentration.
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Naga et al. (1999) studied this question.
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