The new ligand L1 [2-[(E)-2,6-diisopropylphenyl-phenyimino]-2H-acenaphthylen-(1E)-ylidene]-(2,4,6-trimethyl-phenyl)-amine was prepared by stepwise addition of 2,6-diisopropylaniline and 2,4,6 trimethylaniline to acenaphthenequinone. The L1NiBr2 complex crystallized as a pseudo tetrahedral monomer, as determined by single crystal X-ray diffraction. This new catalyst L1NiBr2 and 3 related catalysts, bis(2,6-diisopropylphenyl)acenaphthenediimineNiBr2 (L2NiBr2), [(N,N'-bis-(2,6-diisopropylphenyl)-phenanthrene-9,10-diylidendiamineNi-η3-C3H4COOCH3)]+.{B[C6H3(CF3)2]4-} [(L3Ni-η3-C3H4COOCH3)]+.{B[C6H3(CF3)2]4-} and N-(2,6-diisopropylphenyl)-N'-(2,4,6-trimethylphenyl)-phenanthrene-9,10-diylidenediamineNiBr2 (L4NiBr2) were tested for activity in ethylene polymerization. The super-bulky α-diimine nickel catalysts [(η3- L3NiC3H4COOCH3)]+.{B[C6H3(CF3)2]4-} and L4NiBr2 successfully produced higher molecular weight polyethylene with a high level of linearity compared to the less bulky α-diimine nickel catalysts (L1NiBr2 and L2NiBr2). The super bulky α-diimine backbone helped to compress the reaction space and therefore impede the ethylene insertion to active centre of the catalyst. For this reason, the catalyst activity for super- bulky backbone ligands (L3 and L4) is lower than for their analogous less-bulky backbone ligands (L1 and L2). In general, for both backbones, the nickel catalysts with all-isopropyl substituents produced higher molecular weight polyethylene with less linearity compared to the nickel catalysts with methyl substituents. Moreover, for the acenaphthene backbone, the nickel catalysts with all isopropyl substituents (L2NiBr2) got a higher activity compared to the nickel catalysts with methyl substituents (L1NiBr2). A similar catalyst activity trend was not observed for phenanthrene backboned catalysts. In contrast, L4NiBr2 showed a higher activity compared to [(η3- L3NiC3H4COOCH3)]+.{B[C6H3(CF3)2]4-} For all catalysts, the majority of branches, as characterized by 13C nuclear magnetic resonance, were methyl branches. Polymers with a high level of branches showed a sharp intensity in the loss modulus measured by dynamic mechanical analysis due to a high level of interfacial chains. A reduction in catalyst activity was observed with all nickel catalysts when supported on silica. However, supporting nickel catalysts helps to improve the linearity of the polymer. The same ligands L3 and L4 were used with palladium and successfully produced two new catalysts [L3PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} and [L4PdCH3NCCH3]+.{B[C6H3(CF3)2]4-. Catalyst [L3PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} was more active and produced higher molecular weight and less branched polymer than catalyst [L4PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} in the polymerization of ethylene.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:520698 |
| Date | January 2010 |
| Creators | Alsayary, Omar |
| Contributors | Mair, Frank ; Saiani, Alberto |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/group-4-and-group-10-post-metallocene-ethylene-polymerization-catalysis-catalyst-structurepolymer-properties-relationship(ae5d83a2-4e13-4b8c-b7cc-cf7d67667d3d).html |
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