Copolymerization of norbornene and ethylene

Fig. 4.34 Generic formula of neutral nickel catalysts used in the copolymerization of norbornene and ethylene.

The nickel catalysts described in the preceding section are neutral in character, in our hands cationic nickel catalysts such as those described by Brookhart et al. [20] are ineffective in the copolymerization of norbornene and ethylene. Indeed norbornene has been described as a strong catalyst poison (for both nickel and palladium) by the same workers. Surprisingly we found that cationic palladium catalysts, with a wide variety of chelate ligands, are very effective in the copolymerization of ethylene and norbornenes [89]. These catalysts possess the same ability as the above-described neutral nickel catalysts to incorporate norbornenes bearing functional groups, but overcome two of the major limitations ... 

While the copolymerization of norbornene and ethylene by vanadium and titanium catalysts had been investigated in the 1970s, it was not until the invention of metallocene/MAO catalysts and their application to the homopolymerization of norbornene and other cycloolefins by Kaminsky et ai.8,15,19 that the use of early transition metal catalysts for the addition polymerization of norbornene drew new attention. Nevertheless, the industrial relevance of E/NB copolymers, and the nature of the homopolymers, described in the first reports as insoluble in organic solvents, crystalline, and extremely high melting, focused further investigations on copolymers rather than on norbornene homopolymers. 

For the copolymerization of norbornene and ethylene, different metallocene catalysts having C, C2, C2v, and Cs symmetry were studied by the authors (1-3, Table 16.1, and 4-15, Figure 16.11). The copolymers obtained differ not only regarding the incorporation of norbornene, but also in microstructure and stereostructure, depending on the symmetry of the catalyst used. 

Polynorbornene (PNB) homopolymers of industrial interest are not processible owing to their high TtaS and insolubility in common organic solvents. By copolymerization of norbornene with ethylene, a cycloolefin copolymer (COC) can be produced. These new materials have been the focus of academic and industrial research. Ethylene/norbornene (E/NB) copolymers are usually amorphous and show an excellent transparency and high refractive index, making them suitable for optical applications. ... 

Finally, Kaminsky and Kiesewetter applied a combinatorial screening approach to identify catalysts for the copolymerization of norbornene with ethylene (Kiesewetter and Kaminsky, 2003). Catalysts 83a and 83b (Figure 9.10) were identified and furnished... 

Conventional processes for preparing COCs have some common problems. The conversion of the cycloolefin may be low and further, a high amount of ethylene incorporated results in unsatisfactory low glass transition temperatures. Catalyst compositions have been developed in order to obtain materials with high glass transition temperatures (26). Examples are shown in Table 2.3. These catalysts are used for the copolymerization of ethene and norbornene. 

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. 

Palladium(II) complexes (77a-c) have been prepared from (cod)Pd(Me)Cl (cod = cyclooctadiene-1,5) and pyridinylphosphoranimines (76a-c). Treatment with AgBp4 in MeCN solution affords the corresponding cationic complexes (78a-c), of which (78b) shows the highest catalytic activity in copolymerizations of norbornene with CO or ethylene. ... 

Single site catalysts, such as metallocene compounds, CGCs, and nickel or palladium diimine complexes, used in combination with MAO or borate cocatalysts, are highly active for the homopolymerization of norbornene and its copolymerization with ethylene. The structure of the norbornene homo- and copolymers can be widely influenced by the symmetry and structure of the ligands on the transition metal complexes. 

Organolanthanide complexes can catalyze not only the homopolymerization of ethylene, but also the copolymerization of ethylene with some nonpolar and polar monomers [139, 140], A series of neutral, anionic, and cationic organolanthanide complexes catalyze the copolymerization of ethylene with styrene, a-olefins, methylenecyclopropane, norbornene,... 

Within the family of cycloolefin co-polymers, the most important from a material properties standpoint, are the ethylene/norbornene co-polymers. These co-polymers, dubbed COC for cycloolefin co-polymers, are produced by Ticona and Mitsui under the tradenames Topas and Apel , respectively. An overview of properties and applications (for example, blisters for pills) can be found on Ticona s Topas homepage.607 Detailed ethylene/norbornene copolymerization studies with different 4/-symmetric and ansa-Cp-amido catalysts, with listing of co-polymerization parameters, have been published.608 611 NB is inserted exclusively in the cis-2,3-exo-modc (Scheme 25), and most of the metallocene catalysts tend to produce alternating co-polymers,609 612 due to the low reactivity of the M-NB intermediate toward further NB insertion. This mode of NB insertion prevents f3-H transfer, and thus ethylene/ norbornene co-polymers have increasing molecular masses at increasing NB content.611... 

At B. F. Goodrich we found that this type of catalyst, depicted in the generic structure in Fig. 4.34 (where E = P, As, Sb, O, or N X=O or S Y=saturated or unsaturated hydrocarbyl chain, L is an ancillary hgand), is effective in the copolymerization of ethylene with norbornene-type monomers (both nonfunctional and functionahzed in the 5-position, R-NB) [88]. The appheation of these catalysts for the copolymerization of ethylene and norbornenes was first conceived and demonstrated by our collaborators Makovetsky and Finkelshtein at the Topchiev Institute of Petrochemical Synthesis in Moscow. 

Crowther has reported the copolymerization of ethylene and norbornene using asymmetric cyclo-pentadienyl—amido complexes (132, 133) to yield alternated polymers that melt at 250 °C (Scheme... 

Wehrmann, R, M. Zuideveld, R. Thomann, and S. Mecking, Copolymerization of ethylene with 1-butene and norbornene to higher molecular weight copolymers in aqueous emulsion. Macromolecules... 

Scheme 31.22 NHC-metal-catalyzed copolymerization of CO with (a) ethylene and (b) norbornene.

Copolymerization of Ethylene and Norbornene Using a Neutral Pd-Catalyst... 

Table 8.3 Results of the copolymerization of ethylene and norbornene with the neutral palladium catalyst.

The copolymerizations were carried out under argon using a 1 L Biichi A6 Type I autoclave equipped with an additional external cooling system. For the standard experiments, the reactor was evacuated at 95 C for 1 h and subsequently charged with a solution of norbornene in toluene, 190 mL toluene solvent, 500 mg MAO in 10 mL toluene (from Witco/Crompton), and ethylene at different pressures. Norbornene was dried over triisobutylaluminum and subsequently distilled before use. Polymerizations were initiated by injection of a toluenic metallocene solution into the reaction vessel... 

Catalysts 19 and 20 show notably different polymerization behaviors. Catalyst 19 incorporates norbornene much better than ethylene (Figure 16.13). Even at very low molar fractions of norbornene in the feed (e.g., xn = 0.05), the incorporation of norbornene is at about Yn = 0.44 (Table 16.6, Run 2). When metallocene/MAO catalyst systems are used similarly, it is necessary to carry out copolymerization at feed compositions of up to xn = 0.90 to incorporate norbornene in the same amount. At higher xns with 19, incorporation is nearly independent of feed composition and reaches a plateau of about Yn = 0.60. Polymerizations carried out at xn > 0.60 yielded partially insoluble polymers that were not evaluable by standard C NMR characterization protocols. 

COPOLYMERIZATION OF ETHYLENE WITH NORBORNENE AND ITS FUNCTIONAL DERIVATIVES CATALYZED BY NICKEL COMPLEXES WITH PHOSPHORYLIDE LIGANDS... 

Kaminsky and coworkers foxmd that copolymerization of cyclopentene or norbornene with ethylene, using various metallocene compounds activated with MAO, produced new thermoplastic amorphous materials [55] that were transparent and had high stiffness and excellent stability. 

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