Catalysts Used in Addition Copolymerization of Ethylene and Norbornene

At present the cyclicolefin copolymer is one of the most promising alternative products with high level in the comprehensive utilization of C5 field, which has attracted more attention. The development of metallocene catalysts, non-metallocene catalysts and late transition metal catalysts used in ethylene-norbornene copolymerization are promptly reviewed. Developing new half-sandwich catalysts should be the hot spot in the field of metallocene catalysts. Half-sandwich catalysts can be further divided into two kinds, which are constrained geometry catalysts and Cp' MX3 or Cp' M (R) X-2 (Cp' = cyclopentadienyl group or substituted cyclopentadienyl group; M = Ti, Zr, Hf; X = halogen or alkyl; R = OAr, NR2, NPR3). Non-metallocene catalysts have much more electrophilic metal center and more open active site, which lead to higher norbornene incorporation efficiency. In some certain conditions, it is even able to exhibit the characteristics of quasi-living polymerization. Compared to former transition metal catalysts, late transition metal catalysts should be less sensitive to oxygen and lewis acid, and owns better tolerance against the polar groups. Based on the characteristics of the copolymerization, the catalytic performance is analyzed firstly and then effect of ligand's structure on the catalytic property. Moreover, improving the incorporation efficiency of cyclic olefin and controlling the sequence and molecular weight should be the main focus on this paper. The future research in the area are also prospected.