A-olefins, copolymerization

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... 

Gesattigte und ungesattigte Athylen-a-Olefin-Copolymere 4.3.1. Copolymere des Athylens mit a-Olefinen... 

Copolymerization Parameters for Ethylene/a-Olefin Copolymerization with Various Metallocene/MAO Catalysts 1... 

Table 5. Copolymerization parameters for ethene/a-olefin copolymerization by using different metallocene/MAO catalysts...

LCB-PE (long chain branched polyethylene) is not accessible through simple ethyl-ene/a-olefin copolymerization. Therefore, a bifunctional bimetallic catalyst was developed, in which one active center oligomerizes ethene to long-chain a-olefins, while the other copolymerizes them with ethene. 

Each monomer addition step interconverts the two organometallic components. The poly(methyl methacrylate) (PMMA) obtained is predominantly syndio-tactic, although isotactic PMMA has been obtained by using chiral indenyl zirconocenes in combination with non-zirconocene Lewis acids. No reports of attempted ethylene or a-olefin copolymerizations have been described. 

Alexander KdppI was born in Vilseck, Germany, in 1970. He received his chemical education and his Ph.D. degree at the University of Bayreuth. His dissertation in the research group of Professor H. G. Alt dealt with new support materials for the immobilization of cocatalytically active alumoxanes and their application in ethylene homopolymerization and ethylene/a-olefin copolymerization. He is currently a chemist for BASF AG in Ludwigshafen, Germany. 

Processes of ethene/a-olefin copolymerization are of great practical importance. Copolymerization of ethene with small amounts of highest a-olefins (1-butene, 1 -hexene, 1 -octene) allows one to produce linear low density polyethylene (LLDPE), which is one of the most widely used large-scale polyolefin products. Polypropylene, modified with small amounts of ethene, exhibits higher impact strength compared to isotactic homopolypropylene. Copolymerization of propene with large amounts of ethene and terpolymerization of ethene/propene/diene result in amorphous elastomer materials (rubbers) [103]. 

One of the features of olefin copolymerization kinetics is the effect of comonomer on the rate of ethene or propene polymerization during ethene/a-olefin or propene/ a-olefin copolymerization, i.e., the so-called comonomer effect (CEF). The rate enhancement of ethene or propene polymerization in the presence of a comonomer is observed for conventional ZN catalysts [80, 113-123] and for homogeneous [124-133] and supported metallocenes [134—136] and post-metallocenes catalysts [137-140]. The increase in activity was remarked in the presence of such comonomers as propene, 2-methylpropene, 1-butene, 3-methylbutene,4-methylpentene-l, 1-hexene, l-octene,l-decene, cyclopentene, styrene, and dienes. 

For understanding the nature of the comonomer effect, it is also very important that the rate enhancement takes place in the sequential processes of homo- and copolymerization, i.e., when the ethene homopolymerization is carried out after the a-olefin homopolymerization or ethene/a-olefin copolymerization [122, 123] (Table 6). 

Table 3 Comonomer effect in ethene/a-olefin copolymerization using heterogeneous and supported ZN catalyst systems...

CEF - comonomer effect, Rcop - rate of ethene insertion in ethene/a-olefin copolymerization Rpol -rate of ethene homopolymerization... 

R. Furuyama, M. Mitani, J.-L Mobii, R. Mori, H. Tanaka, T. Fujita, Ethylene/higher a olefin copolymerization behavior of fluminated bis(phenoxy- imine) titanium complexes with methylalumoxane synthesis of new polyethylene-based block copolymers. Macromolecules 38(5), 1546-1552 (2005)... 

Jang Y-J, Nenov N, Klapper M, Mullen K (2003) Organic nanoparticles with polypropy-leneoxide chains as support for metallocene catalysts ethylene homopolymerization and ethylene/a-olefin copolymerization. Polym Bull 50 343-350... 

The standard kinetic scheme for ethylene/a-olefin copolymerization reactions usually includes several chain initiation reactions, chain propagation reactions, and chain termination reactions as shown below. In this scheme, C represents an active center and m is the number of ethylene and/or comonomer units in a polymer chain. 

In ethylene/a-olefin copolymerization reactions, those centers that incorporate an a-olefin into the polymer chain poorly (Centers IV and V) retain this high reaction order (n > 1), while the reaction order changes to first order for those centers that incorporate an a-olefin into the polymer chain well (Centers I, II, and III). 

Oct-2-enylsuccinic anhydride, 166 Octyl acrylate, MA copolymerization, 296, 521, 522 a-Olefin copolymerizations, with MA by Ziegler, 289, 293... 

A very wide variety of catalysts and comonomers has been investigated in metallocene-mediated ethylene/a-olefin copolymerization. Table 6 catalogs several of these, along with their... 

Table 6 Comparison of reactivity ratios for ethylene/a-olefin copolymerizations between heterogeneous ZN systems (entries 1-2) and several metallocene/MAO catalyst systems (3-13)... 

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