High molecular weight polymers complexes

Carbon monoxide also reacts with olefins such as ethylene to produce high molecular weight polymers. The reaction of CO with ethylene can be initiated by an x-ray irradiator (62) or transition-metal cataly2ed reactions (63). The copolymeri2ation of ethylene with carbon monoxide is cataly2ed by cationic Pd (II) complexes such as Pd[P(CgH )2] (CH CN) (BF 2 where n = 1-3. With this catalyst, copolymeri2ation can be carried out at 25°C and pressures as low as 2.1 MPa. 

The olefins that undergo metathesis include most simple and substituted olefins cycHc olefins give linear high molecular-weight polymers. The mechanism of the reaction is beheved to involve formation of carbene complexes that react via cycHc intermediates, ie, metaHacycles. Industrial olefin metathesis processes are carried out with soHd catalysts (30). 

Similarly, Thompson(33) showed that the addition of trace quantities of high molecular weight polymer to solvent reduced friction loss during turbulent flow of the solution. As knowledge of the characteristics needed to do more than change solution rheology grew, complex polymers were prepared and applied. 

In conclusion one can say that SEC is a very powerful method for polymer characterization, especially in combination with other composition sensitive or absolute calibration methods. A big advantage is also that the sample amount is fairly small, typically 10 mg. For more complex polymers, such as polyelectrolytes, enthalpic effects often become dominant and also for rather high molecular weight polymers chromatographic methods such as field-flow fraction (FFF) techniques might be more suitable. For fast routine measurements linear columns are often used. 

The above organolanthanide complexes are less effective in obtaining high molecular weight polymers of (Lmethylpropiolactone. However, random... 

Conjugation between the imino and acyl [121], or nitrile (in complex 1.47) [122] moieties permitted the remote activation of nickel. Another catalyst (1.48) exhibiting coordination via an alkenyl moiety is noteworthy because of its sterically small size, which should prohibit the production of high molecular weight polymers [123], This is believed to be possible because of the catalyst s unique electronic properties. As bulkier imino-aryl substituents are introduced, polymerization activity and polymer molecular weight increases, as expected [124],... 

Cobalt complexes are used for the living radical polymerization of acrylates to give a high molecular weight polymer with a narrow molecular weight distribution (Mw/Mn 1.2) (Eq. 71), whereas the complex is applied to the introduction of an unsaturated group into the methacrylate polymers with a high efficiency via a reaction mechanism illustrated in Eq. (72) [27,28,267,268]. 

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