The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Chemical Technology for public examination and debate in Auditorium KE2 at Helsinki University of Technology (Espoo, Finland) on the 21st of September, 2007, at 12 noon.
Overview in PDF format (ISBN 978-951-22-8898-4) [686 KB]
Dissertation is also available in print (ISBN 978-951-22-8897-7)
Three novel transition-metal complexes were studied as catalysts in ethylene polymerization. The aminopyridinato complexes bis(2-benzylaminopyridinato)trichlorotantalum(V) and trichlorobis[2,6-di(phenylamino)pyridinato-N,N']tantalum(V) exhibited moderately high catalytic activities when activated by methylaluminoxane (MAO). The ethylenebis(salicylideneiminato)zirconium dichloride/MAO showed low activity when used as a homogeneous system, but activities were moderate when it was supported on silica. Under industrially relevant conditions all three systems yielded polyethylene with linear structure and moderately high molar mass.
Oxygen- and nitrogen-functional alkenes were studied as comonomers in copolymerizations with ethylene and propylene catalyzed by bridged zirconocene/MAO catalysts. The presence of comonomer decreased the activity of the catalyst. The magnitude of the decrease was dependent on the nature of the functional group. Among the oxygen-functional comonomers the alcohols and ethers performed better, whereas the ketone and the less shielded ester had a stronger poisoning effect. Similarly, amines were better tolerated than the corresponding amides. In general, the more shielded comonomers had slightly less negative effect on the catalyst activity.
The interactions of several oxygen-functional comonomers with metallocene catalyst components were investigated by NMR. The reactions were found to depend on the nature of the functionality. The alcohols formed aluminum alkoxides with MAO, whereas the ethers remained mainly in the form of free comonomers. Nevertheless, these comonomers behaved in the same way in copolymerizations, which suggests that alkoxide formation is not a prerequisite for copolymerizability.
Functionalized polyolefins with reactive alcohol, acid, ester, ether, amine, or amide groups were synthesized. The maximum amount of comonomer in the polymer was 3.6 mol %. NMR and DSC studies indicated that the comonomer was randomly distributed in the polymer chain. The molar masses of the copolymers were lower than those of the corresponding homopolymers. The functionalized polyethylenes were found to act as effective compatibilizers in polyethylene/polyamide 6 blends, increasing both toughness and stiffness.
This thesis consists of an overview and of the following 7 publications:
Keywords: functionalized polyolefin, metallocene, single-site catalyst, ethylene, propylene, copolymerization
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© 2007 Helsinki University of Technology