Propylene polymerization, catalyst copolymerization

The first enantiomer-selective polymerization was performed with propylene oxide (172) as a monomer [245], The polymerization was carried out with a ZnEt2/(+)-bor-neol or ZnEt2/(-)-menthol initiator system. The obtained polymer was optically active and the unreacted monomer was rich in (S)-isomer. Various examples are known concerning the polymerization and copolymerization of 172 [246-251 ]. A Schiff base complex 173 has been shown to be an effective catalyst In the polymerization at 60°C, the enantiopurity of the remaining monomer was 9% ee at 50% monomer conversion [250],... 

Dinuclear and trinuclear ferrocenyl derivatives of the type [CpFe(/i-C5H4SiMe2C5H3R R2)ZrCpCl2] (R = R = H R = Me, R = H R = R = Me R = Ph, R = H) and [ CpFe(/r-C5H4SiMe2C5H4) ZrCl2] are very active olefin polymerization catalysts and the former type is active in the copolymerization of ethene and propylene or the terpolymerization of ethylene, propylene and ethylidene-2-norbomene.[ l... 

The issue begins with an article by Ittel, Johnson, and Brookhart on late metal catalysts for ethylene homo- and copolymerization. They detail the newest generation of catalysts to be commercially licensed. Alt and Koppl then introduce ethylene and propylene polymerization by metallocene catalysts. Structure-performance relationships for unbridged and bridged... 

A number of metal-catalyzed polymerizations have utilized CO2 as both a solvent and as a reagent in the reactions. Precipitation copolymerization of either propylene oxide (83) or cyclohexene oxide (84) with CO2 in SCCO2 has been catalyzed using heterogeneous zinc catalysts. Copolymerizations of CO2 and propylene oxide formed PCs with a molecular weight of about 10 g/mol and incorporation of CO2 at greater than 90% (eq. (7)). A small percentage of propylene carbonate by-product was also observed. 

Table 5.8 lists propylene polymerization data for some of the complexes shown in Figure 5.12. Varieties of other polymer products have been prepared using the D/A-bridged complexes. For example the (Flu)(Cp)ZrCl2 complexes (22a-b) produce ultra-high molecular weight (UHMW) polyethylene with intrinsic viscosities as high as 13.5 d/g. The D/A metallocenes are also effective catalysts for the copolymerization of a-olefins with ethylene to produce medium to ultta-low density polyethylene products. ... 

Unlike molecules containing electron-rich heteroatoms, boron compounds do not poison Ziegler-Natta or metallocene polymerization catalysts. Borane-containing olefin comonomers are therefore well suited to produce olefin copolymers while retaining good catalyst activity. The resulting polymers are suitable for subsequent conversion into a variety of functional groups. In principle, two approaches are possible (1) hydroboration of the terminal double bond (formed by typical chain transfer processes) of a preformed polyolefin, and (2) direct copolymerization of propylene or a 1-alkene with an alkenyl borane (Scheme 11.4). 

Tacticity measurements can be correlated with reaction mechanisms and physical properties. For example, the incorporation of an electron donor into the polymerization catalyst formulation has been found to increase isotacticity in a propylene-1-butene copolymer [123], and the distribution of propylene and 1-butene contents as a function of molecular weight varied, depending on donor type. External donors, such as dimethox-ysilane, decrease the butene content more than internal electron donors (in this case, di-n-butyl phthalate). Mechanisms of new polymerization reactions, such as the group-transfer copolymerization of methyl methacrylate and lauryl methacrylate, can be elucidated by comparing NMR-derived structural details [124]. The presence of unanticipated peaks in the spectrum of poly(ethylene-co-norbomene) suggest the occurrence of epimerization... 

Despite the low catalyst activity, all studied amides 19—23 formed copolymers with ethylene and propylene. The maximum amount of amide incorporated was 1.3 mol% with ethylene and 0.96 mol% with propylene. In the copolymerizations of amines with ethylene, the highest comonomer contents were on the same level (1.2 mol%), even though much higher comonomer concentrations could be used in the polymerizations. It seems that when the functional comonomers are better masked by the cocatalyst, the reactivities are at the same time decreased. Nonetheless, even the unhindered primary and secondary amines with acidic hydrogens were incorporated in the polymer chain. In this respect, the amines behave much like the alcohols and ethers, whereas amides resemble the less-shielded esters. 

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