Cyclopolymerization of 1,7-octadiene with metallocene/methylaluminoxane

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.