To investigate dinuclearity and bridge effects on the catalyst performance and some polyethylene properties, two binuclear and a mononuclear α-diimine Ni-II--based catalysts were comprised. Diphenyl Bi-Nuclear catalyst -DBNC- with a structure showed the highest activity -1750 g PE/mmolNi. h.- at the same ethylene polymerization condition while the bi-nuclear catalyst -BNC- illustrated moderate activity -1073 g PE/mmolNi. h.- and mono-nuclear catalyst -MNC- with no activity. This observation assigned to synergistic dinuclearity and cooperative effects which increased as the length, flexibility and thermal stability of bridge increased in DBNC -biphenyl methylene spacer-. DSC thermograms revealed that polymer resulted using DBNC has insignificant crystallinity degree less than 1% with melting point at 117.2 °C, however, BNC yielded polyethylene with 24.7% crystallinity and Tm=123.0 ˚C. The vinyl content and branching of resulted PE in presence of catalyst DBNC were 21.2 and 101, however, these quantities decreased to 9.1 and 78 for catalyst BNC, respectively.

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