Metal complexes with enolatoimine ligands for controlled olefin polymerizations

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YU, Sze-Man, 2009. Metal complexes with enolatoimine ligands for controlled olefin polymerizations

@phdthesis{Yu2009Metal-9763, title={Metal complexes with enolatoimine ligands for controlled olefin polymerizations}, year={2009}, author={Yu, Sze-Man}, address={Konstanz}, school={Universität Konstanz} }

2009 2011-03-24T18:14:14Z 2011-03-24T18:14:14Z Yu, Sze-Man The physical and mechanical properties of a polymer are determined by its morphology, which in turn is dependant on the molecular microstructure. Therefore, catalyst development which enables control of polymer microstructure is studied intensely. However, nascent morphologies can also be determined by appropriate catalysts in combination with appropriate reaction conditions, e.g. nanoscale compartmented systems. Significant advances, specifically concerning control of molecular weights by living polymerization, branching and generation of nanoscale polymer crystals in aqueous systems have been made recently with metal complexes of salicylaldiminato ligands. This thesis reports the polymerization properties of structurally related enolatoimines, which are rendered relatively electron-poor by a trifluoro-substitution of the enolato-moiety.<br />Chapter 3 describes well-defined Ni (II) methyl complexes [(N^O)NiMe(L)] which are rendered water-soluble by a sulfonated or polyethyleneglycol-substituted ligand L. Aqueous solutions of these complexes are precursors to very stable catalysts, which polymerize ethylene at elevated temperature (70 °C) to dispersions of nanoscale (≤ 30 nm) crystals. The polymer branching, and consequently the degree of crystallinity, can be varied via the substitution pattern of the enolatoimine ligands.<br />Chapter 4 addresses the polymerization properties of titanium complexes [(N^O)2TiCl2]. With an appropriately substituted enolatoimine, linear polyethylene with unprecedented molecular weight distributions of Mw/Mn = 1.01 and at the same time high molecular weights of > 105 g mol-1 is obtained, block copolymers with an atactic polypropylene block are described. The non-living nature of polymerization with related complexes goes along with an inefficient activation by the MAO cocatalyst.<br />Chapter 5 reports the preparation, structure and reactivity of the catalyst precursors utilized in Chapter 4. For the cases of the enolatoimine ligands subject to this thesis, reaction of the corresponding ketoenamine with [Ti(NMe2)2X2] to the amine complexes [(N^O)2Ti(NMe2)X] was found to be a more general entry.<br />Chapter 6 describes the preparation, structure and reactivity of analogous zirconium complexes [(N^O)2ZrCl2]. Activated with MAO, theses complexes polymerize ethylene with high activity in a non-living fashion. Sterically bulky o-substituents on the N-aryl moiety profoundly hinder activation and/or chain growth and even more chain transfer, resulting in high molecular weight polymer.<br />Chapter 7 covers the synthesis and characterization of copolymers from ethylene and cyclopentene by an ortho-fluorinated enolatoimine Ti complex. High molecular weight copolymers with exclusive cis-1,2 cyclopentene units and low molecular weight distributions were found. Under optimal reaction conditions, 50 mol % cyclopentene were incorporated to a perfectly alternating iso-enriched copolymer. Metallkomplexe mit enolatoimin Liganden zur kontrollierten Polymerisation von Olefinen Metal complexes with enolatoimine ligands for controlled olefin polymerizations application/pdf deposit-license Yu, Sze-Man eng

Dateiabrufe seit 01.10.2014 (Informationen über die Zugriffsstatistik)

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