Norbornene-terminated poly

Ni(fJ,l r)2. In an effort to lower the molecular weight of the polymer chain and simplify analytical characterization, homopoiymerization of norbornene was carried out in the presence of ethylene pressure. Norbornene polymerizations catalyzed by cationic nickel catalysts such as (// -crotyl)Ni(1,5-fX)l)) ld, are quite susceptible to acyclic olefins as chain transfer agents and produce substantially reduced molecular weight vinyl-terminated poly(norbornenes) (Section 4.2.3.5). 

Polymacromonomers of polystyrene (PS), poly(ethylene oxide) (PEO) and polybutadiene (PB) could be prepared [1,8] by ROM homopolymerization of various norbornene-terminated macromonomers. Complete conversions were achieved,... 

The polymerization proceeds without termination or chain transfer to give poly-norbomene with a narrow molecular weight distribution [35], After an induction period, the rate of monomer consumption (rate of polymerization) becomes constant, indicating a zero-order dependence on the monomer concentration. The induction period is caused by part of titanacycle 7 undergoing non-productive, but rapidly reversible, cleavage to norbornene and the titanium methylene complex, Eq. (17 a). 

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