Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.
Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.
(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)
Design and synthesis of novel group IV metallocenes for the Ziegler -Natta type polymerization of alpha-olefins
Four new substituted indenyl-fluorenyl asymmetric ethylene bridged ligands have been prepared from the reaction of 1-(9-fluorenyl)-2-bromoethane and the lithium salt of the desired indenyl moiety. The ligands have been converted to the corresponding substituted asymmetric ethylene-bridged metallocenes (M = Zr, Hf). The metallocenes have been evaluated as Ziegelr-Natta type catalyst precursors for the polymerization of ethylene and propylene. The zirconocene complexes 19-21 showed very high activity for both monomers. The influence of substitution on the selectivity of the propylene polymerization has been studied. The metallocene 1-(9-fluorenyl)-2-[(2,4,7-trimethyl)-1-indenyl] ethane zirconium dichloride (21) was found to produce highly isotactic polypropylene with [mmmm] of 89%. ^ The dimethylsilylene bridged analog of 21 (31) was prepared and was found to be less active and less stereoselective than the ethylene bridged precursor. A detailed study of the propylene polymerization behavior of the zirconocene complexes (19-21, 31) was carried out and the mechanistic aspects of polymerization are discussed. ^ Three new zirconocenes bearing 2,4-disubstitution on the indenyl moiety have been synthesized and evaluated as (x-olefin polymerization catalysts. For the new complex, ethylene-1-(9-fluorenyl)-2-[1-(2-methyl4-phenyl)indenyl]zirconium dichloride (42), highly isotactic polypropylene with [mmmm] = 91% and Mw = 1.1 x 105 was produced in very high yield. The dimethylsilylene analog (44) while less active, gave similar results in terms of stereoregularity with a two-fold increase in MW. ^ Two new asymmetric complexes with partially or fully substituted fluorenyl ligands have been synthesized. Dimethylsilylene-[1-(2-methyl-4-phenyl)indenyl-(9-tetrahydrofluorenyl) zirconium dichloride (51) and the octahydrofluorenyl analog 52 were highly active catalyst precursors for ethylene and propylene polymerizations with activities approaching 108 g polymer/[(mol Zr) [monomer] h]. The polypropylenes produced at room temperature were highly isotactic. ^ Several new, novel bridged and unbridged bis-tetrahydrofluorenyl zirconocenes were synthesized. The complexes were found to be highly stable compared to some bis-fluorenylzirconocenes. Polypropylene and polyethylene were produced in good yield using the new catalyst precursors with MAO or Trityl/TIBA as co-catalysts. ^
Thomas, Emma Jane, "Design and synthesis of novel group IV metallocenes for the Ziegler -Natta type polymerization of alpha-olefins" (2000). Doctoral Dissertations Available from Proquest. AAI9978565.