Nickel norbornene polymerization with

The (co-)polymerization of functional monomers was also explored with the Ni and Pd catalyst systems. The multi-component Ni catalyst (Ni(O2CR)2 -i-HSbFg-i-OBFs LlyO-i-lOAlLlj) works very well for the copolymerization of norbornene and 5-triefhoxysilylnorbornene. The copolymerization of norbornene and with 5-10 mol% 5-triethoxysilylnorbomene monomers yields a high molecular weight copolymer of fhe same molar composition in excellent yield (85%) at a 4000 1 monomer to nickel molar ratio. 

These nickel-hased compounds with P-O ligands also proved to he capable of ter-polymerizing norbornenes and ethylene with 1-alkenes. As in copolymerizations with ethylene, the level of incorporation of 5- -butylnorbornene in the terpoly-mers was lower than that of norbornene. Additionally, the molecular weights obtained were lower, suggesting that the incorporation of the 1-alkene facilitates chain termination. 

Tab. 4.1 Polymerization of norbornene and 5-decylnorbornene using catalyst 1 (naked nickel) with and without 1-decene as a chain transfer agent.

The polymerization of norbornene using catalyst 2 is much more sluggish than with 1. Even after 24 h (albeit at a 4000 1 molar ratio of norbornene to palladium) in 1,2-dichloroethane, only 66% conversion to poly(norbornene) was achieved. The difference in rate observed between nickel and palladium was used to our benefit in determining fhe initiation event, as explained in the following section. 

Albeit these catalysts display a limited stability to water, activities of 3 X lO TO h at room temperature are observed. As with the polymers obtained in traditional polymerization in organic solvents, the materials obtained in water with sal-icylaldimine-based nickel(II) complexes possess a moderate number of methyl branches. Overall, as in the case of the linear polyefhylenes obtained with 6 to 8, the presence of water has no effect on the basic polymer microstructure. Polymer crystallinity can be influenced by employing norbornene as a co-monomer. High molecular weight, amorphous efhylene-norbomene copolymers, which form films at room temperature, can be obtained in aqueous polymerizations [71]. 

Iron- and cobalt-based catalysts " " have been reported to be active for the polymerization of norbornene, especially when activated with MAO. Similar to the case of many nickel and palladium catalysts, PNBs generated with simple salts such as cobalt neodecanoate are similar to PNBs prepared with ligand-bearing catalysts (e.g., Brookhart-Gibson type pyridyldiimine cobalt catalysts). 

Nickel-0- and palladium-O-complexes are very active catalysts for the polymerization of norbornene and also for cyclopentene [552-554], Nickel catalysts produce soluble polymers with a molecular weight of over one million while polymers obtained with palladium or metallocene complexes are insoluble. The soluble polymers have an atactic structure. The microstructure of the polynorbornene depends on the catalyst used and is isotactic by synthesis with chiral metallocenes. 

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