Polymerization of norbornene was carried using a (MC) and two dinuclear (DC1 and DC2) a–diimine Ni-based catalysts under controlled conditions. The structure of dinuclear catalysts had a difference on the ortho- and para position (2,4.6-trimethyl group for DC1 and 2, 6-isopropyl group for DC2). DC2 catalyst through synergistic effects exhibited higher productivity (1.3_106 g/ mol Ni) in comparison to DC1 catalyst (1.0_106 g/mol Ni) and MC catalyst (0.8_106 g/mol Ni). Moreover, molecular weights of the polynorbornene (PN) made by DC2 catalyst (Mw ¼ 9.0_105 g/mol and Mv ¼ 5.1_105 g/mol) were greater than the sample obtained by DC1 (Mv ¼ 3.1_105 g/mol) and MC (Mw ¼ 4.7_105 g/mol and Mv ¼ 2.4_105 g/mol). Reaction parameters especially polymerization temperature showed a significant impact on catalyst productivity and molecular weight of the samples. Thermal analysis including DSC, DMTA and TGA employed to characterize the PNs and revealed that the sample obtained by DC2 catalyst had a much uniform and stereoregularity in microstructure, while for MC, results were slightly different. Based on this, the Tg of the PN made by the DC2 catalyst was distinctive, and the DTGA curve was unimodal. The microstructural study of PNs was carried out using 13C NMR and confirmed the observed properties.

Keywords