Studies On Synthesis, Characterization And Catalysis For Olefin Polymerization Of Constrained Geometry Metallocene Catalysts

In the last two decades, the so-called constrained geometry metallocene catalysts (CGC) with the general formula of [η5:η1-C5R4(SiMe2)NR1]TiCl2 (I in Chart 1) have been widely studied in academic [1-4] and industrial [5-8] institutions because of their high performance in catalyzing the copolymerization of different olefins. Various modifications on the chelating ligands have been made in order to improve the catalytic performance of the CGC catalysts through steric and electronic effects of their ligands.In this paper, ten new compounds were synthesized including three ligands and three Ti complexes. These complexes were characterized by by means of 1H and 13C NMR spectroscopy and elemental analysis, and single crystal X-ray crystallography. The catalytic properties of the Ti complexes for the compolymerization of ethylene/a-olefins and ethylene/5-ethylidene-2-norbornene were investigated.In chapter two, we have synthesized three new ligangd:2-(Me4C5H)-4-Me-6-Ad-phenol,2-(Me4C5H)-4-tBu-6-Ad-phenol, and 2-(3,4-Ph2C5H2)-4-'Bu-6-Ad-phenol from the reaction of their corresponding phenol-lithium with 2,3,4,5-tetramethylcyclopent-2-enone. And three new half sandwich titanium. [η5:η1-2-C5Me4-4-Me-6-AdC6H2O]TiCl2 (8), [η5:η1-2-C5Me4-4-tBu-6-AdC6H2O]TiCl2 (9) and [η5:η1-2-C5H2Ph2-4-tBu-6-AdC6H2O]TiCl2 (10) were synthesized from the reaction of their corresponding ligand with TiCl4. These new Ti complexes were characterized by means of 1H and 13C NMR spectroscopy and elemental analysis, and the structures of [η5:η1-2-C5Me4-4-Me-6-AdC6H2O]TiCl2 and [η5:η1-2-C5Me4-4-tBu-6-AdC6H2O]TiC12 were determined by single crystal X-ray crystallography.In chapter three, the catalytic performance for 5-ethylidene-2-norbornene (ENB) homopolymerization and ethylene/ENB copolymerization using 8-10 constrained geometry catalysts in the presence of Al'Bu3 (TIBA) and [Ph3C][B(C6F5)4] (B) were investigated. The three catalyst systems show good activity on the homopolymerization of ENB, and higher activity of on the copolymerization of E/ENB under atmosphere pressure of ethylene. 1H NMR analysis of polymer indicates that ENB was inserted into polymerchain through the endocyclic double bond regiosectively. leaving the ethylidene double bond unreacted.1H NMR analysis of polymer also indicates that the catalyst systerm of 9/TIBA/B showed better steroselectivity in homopolymeriztion of ENB than the catalyst systerm of 11 or 12/TIBA/B. In comparence with the catalyst systerm of 11/TIBA/B, the catalyst systerm of 9 showed higer capability of comomoner incorporation under the same condition. The effects of the polymerization temperature and initial ENB concentration on the catalytic activity, content of ENB in the copolymer, molecular weight of copolymer, and glass transition temperature of copolymer were examined. The relation between the structure of the complexes and their catalytic properties was explained.In chapter four, the catalytic performances for ethylene/1-hexene copolymerization of 8-11 catalyst systerms were investigated. The results of GPC analysis showed that the result copolymer obtained by 9/TIBA/B has a little higher molecular weight thant that obtained by 11/TIBA/B. Copolymerization of ethylene with 1-octadecene using constrained geometry catalysts 2-(tetramethylcyclopentadienyl)-4, 6-di-tert-butylphenoxytitanium dichloride (11), 2-(tetramethylcyclopentadienyl)-6-tert-butylphenoxytitanium dichloride (12), 2-(tetramethylcyclopentadienyl)-6-methylphenoxytitanium dichloride (13). and 2-(tetramethylcyclopentadienyl)-6-phenylphenoxytitanium dichloride (14) was studied in the presence of TIBA/B were studied. The effects of the catalyst structure, and reaction parameters such as the Al/Ti molar ratio, polymerization temperature, and comonomer feed concentration on the catalytic activity, comonomer incorporation, and molecular weight of the copolymers were also examined. The reactivity ratio product (rE·rOD was 1.039) values is close to 1, which demonstrates that the ethylene/1-octene and ethylene/1-octadecene copolymerization proceeds in a random manner. Among the four catalyst systems 11/TIBA/B showed the highest activity and the result copolymer obtained by 12/TIBA/B has the highest molecular weight under the same condition. The catalyst systerm of 14/TIBA/B showed the lowest activity among the four catalytic systerms. The relation between the structure of the complexes and their catalytic properties was explained.