Ethene Copolymerizations

Water-soluble dicationic palladium(II) complexes [(R.2P(CH2)3PR.2)Pd-(NCMe)2][BF4]2 proved to be highly active in the carbon monox-ide/ethene copolymerization under biphasic conditions (water-toluene). In the presence of an emulsifier and methanol as activator, the catalytic activity increased by a factor of about three. Also higher olefins could be successfully incorporated into the copolymerization with CO and the terpolymerization with ethene and CO.184... 

Ethene, copolymerization of, 76 111 Ethene homopolymerization, 76 102-103 l-Ethenyl-2-pyrrolidinone. See AT-Vinyl-2-pyrrolidinone... 

Water-soluble l,3-bis(di(hydroxyalkyl)phosphino)propane derivatives were thoroughly studied as components of Pd-catalysts for CO/ethene (or other a-olefins) copolymerization and for the terpolymerization of CO and ethene with various a-olefins in aqueous solution (Scheme 7.17) [59], The ligands with long hydroxyalkyl chains consistently gave catalysts with higher activity than sulfonated DPPP and this was even more expressed in copolymerization of CO with a-olefins other than ethene (e.g. propene or 1-hexene). Addition of anionic surfactants, such as dodecyl sulfate (potassium salt) resulted in about doubling the productivity of the CO/ethene copolymerization in a water/methanol (30/2) solvent (1.7 kg vs. 0.9 kg copolymer (g Pd)" h" under conditions of [59]) probably due to the concentration of the cationic Pd-catalyst at the interphase region or around the micelles which solubilize the reactants and products. Unfortunately under such conditions stable emulsions are formed which prevent the re-use... 

Figure 7.7 Selected P H NMR spectra recorded during a CO/ethene copolymerization assisted by [Pd TFA)2(Na2DPPPDS)] in the presence of 20 equiv of TsOH and a 1 1 CO/C2H4 pressure of 600 psi (10 mm sapphire tube, D2O, 20—85°C,...

Studies of ethene copolymerization with 1-butene using the Cp2ZrCl2/ MAO catalyst indicated a decrease in the rate of polymerization with increasing comonomer concentration. 

A conventional approach to fhe controlled formation of short-chain branches is ethene copolymerization wifh co-monomers such as propene, butene(l), 4-mefhyl-pentene(l), hexene(l) or octene(l). In the ethene/propene copolymerization example given below an increased number of methyl groups compared with vinyl end groups is consistent wifh a propene incorporation of approximately 6 mol% [Eq. (13)], fhe observed lower DSC melt temperatures and lower densities are typical for medium density (MDPE) and hnear low density polyethylene (LLDPE). 

Scheme 8.3 Proposed catalytic cycle for the growing steps of the CO-ethene copolymerization starting with [Pd(dppp)(CH3)(OSO2CF3)] (GPC=growing polymer chain).

Scheme 8.6 Various chelate di-phosphorus ligands used for palladium-catalyzed carbon monox-ide-ethene copolymerization.

Scheme 8.8 Various palladium catalyst precursors modified with hybrid ligands for the carbon monoxide-ethene copolymerization.

Ethene copolymerizations have been thoroughly studied during recent years. A lot of work remains to be done in this area, however, in particular on termination and chain-transfer processes. The progress in these investigations is correlated to improvements achieved in the quality of copolymer MWD analysis. 

Nearly 40 years have evolved between the first discovery by Reppe of transition-metal-catalyzed CO/ethene copolymerization and the discovery in 1983, at Shell, of a class of highly active, high yield palladium catalysts for the synthesis of high molecular weight, perfectly alternating CO/ethene copolymers [PK-E, Fig. 1], This class of catalysts is also active for the co- and terpol5unerization of CO with alkenes other than ethene, both simple aliphatic and heteroatom functionalized, thus providing access to a family of completely new polyketone polymers. 

Table 2. Performance of Selected Catalysts in CO/Ethene Copolymerization ...

Schneider, M. J. Suhm, J. Muelhaupt, R. Prosenc, M.-H. Brintzinger, H.-H. Influence of indenyl ligand snbstitution pattern on metallocene-catalyzed ethene copolymerization with 1-octene. Macromolecules 1997, 30, 3164—3168. 

Kaminsky copolymerized higher condensed cyclic olefin comraiomers such as DMON or TMDA using metallocene catalysts [38, 98]. Low activities in DMON-ethene copolymerization and low incorporation were observed because of the increasing monomer bulk. Although the reactivity ratio for norbomene is similar to that of propene, reactivity ratios for DMON and TMDA are comparable to those of 1-butene and 1-hexene. 

The variation of reactivily ratios with pressure is minor, as it is the difference between the activation volumes for homopropagation and cross-propagation that determines the formal activation volume of r. AV (ri)=-(d In rildp iRT. As a consequence, the accurate measurement of the resulting small activation volumes poses problems, which is especially true for AV (rx), as the comonomer content of the feed is mostly rather low. On the other hand, because of the small size of AV (r), this number need not be known overly accurately. Moreover, the pressure range of ethene copolymerizations is not very extended, as pressure is limited toward high p for technical reasons and toward low p by inhomogeneity of the reaction mixture. 

Palladium-Catalyzed CO/Ethene Copolymerization 9 Table 1.3 Platinum/tin-catalyzed hydroformylation of 1-octene at E0°C.°... 

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