Synthesis and structural characterization of ethylene-norbornene copolymer with high norbornene content catalyzed by β-diketiminato nickel/methylaluminoxane

摘要

Ethylene-norbornene (E-N) copolymerizations were carried out by using β-diketiminato nickel complexes CH{C(CF_3)NAr}_2NiBr (Ar = 2,6-~iPr_2C_6H_3, 1; Ar = 2,6-Me_2C_6H_3, 2) in the presence of methylaluminoxane (MAO). Complex 1 bearing bulky isopropyl ortho substituents showed higher activity than 2 for the E-N copolymerization. The activity of the catalytic systems increased with increasing the feed ratio of norbornene/ethylene (N/E), and gave the E-N copolymers with high norbornene content more than 75 mol%. In the microstructures of copolymers generated with the catalytic systems, norbornene microblocks with a length of two or three norbornene units have been detected. Results have shown that the activity and the content of norbornene in copolymer depend on the N/E feed ratio.