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Studies on Synthesis,Characterization and Catalytic Performance for Olefin Polymerization of Novel Metallocene Catalysts

Author: LiuKeFeng
Tutor: MuZuo
School: Jilin University
Course: Organic Chemistry
Keywords: Metallocene catalysts Zirconium complexes Titanium complexes Ethylene polymerization Copolymerization
CLC: O631.5
Type: PhD thesis
Year: 2011
Downloads: 124
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Abstract


Polyolefin has been one of the widely used synthetic polymers in our daily life, and the market capacity is still increasing in the conventional polyolefins such as polyethylene (HDPE. LLDPE). polypropylene (PP). Considerable attention has been recently paid to producing new polyolefins with specified function such as optical materials by COC (cyclic olefin copolymer). alternatives for poly(vinyl chloride) by ethylene/1-hexene copolymer and others. This is also due to that the use of polyolefins should be considered (especially from the aspect of contribution in the reduction of undesirable by-product and/or waste), because the recycling should be easier than other specified polymers and the monomer synthetic procedure should be shorter than the other functionalized monomers. It is highly believed that the design and synthesis of efficient transition metal complex catalysts that precisely control olefin coordination polymerization is the key for synthesizing new polyolefins that have never been prepared by the conventional catalysts. Therefore, researches concerning design of efficient transition metal complex catalysts for controlled precise olefin polymerization have attracted considerable attention in the field of catalysis, organometallic chemistry, as well as in the field of polymer chemistry. Recent progress in the newly designed catalysts has offered the new possibility for evolution of new polymers.Metallocene type catalysts can produce a variety of polyolefin products with high performance such as isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, high density polyethylene, linear low density polyethylene, syndiotactic polystyrene, and cyclo-olefin copolymer and so on. In view of the success of metallocene-based catalysts in catalyzing the above mentioned olefin polymerization reactions, we have great interest in synthesizing new metallocene catalysts for olefin polymerization, and exploring the effect of substituent of the ligand and polymerization conditions on the composition and structure of the polymer, and we can synthesize polyolefin product with high performance by optimizing the catalyst structure and polymerization condition.Conclusions were summarized as follows:In Chapter Two, A number of half-sandwich titanium(IV) complexes bearing an anilide ligand with a general formula of Cp’TiCl2[N(2.6-R21C6H3)R2] have been synthesized. The molecular structures of three complexes were confirmed by X-ray crystallography. Upon activation with AliBu3/Ph3CB(C6F5)4, all complexes were explored in ethylene polymerization and copolymerization with 1-hexene. The catalytic activity of these complexes is notably influenced by the nature of the substituents on the Cp’ ligands. The titanium complexes with Cp* ligand showed much higher catalytic activity than the the Cp based complexes for both ethylene polymerization and ethyl ene/1-hexene copolymerization. The titanium complexes with Cp ligand produced ultra-high molecular weight (Mη>3×106 g/mol) polyethylene. The Cp* based complexes exhibited obviously higher catalytic activity in ethylene copolymerization with 1-hexene producing ethylene-co-l-hexenes with higher molecular weight (Mw=20×10-4g/mol) and comonomer content (1-hexene content, up to 36%). The Cp based complexes exhibited relatively low catalytic activity for ethylene/1-hexene copolymerization, and produce copolymer with relatively low molecular weight as well as comonomer content.Because of the good perfornance of half-sandwich titanium(Ⅳ) complexes bearing an anilide ligand in Chapter Two, In Chapter Three, the analogue zirconium complexes of the type Cp*ZrCl2[N(2.6-R21C6H3)R2] and Cp*ZrCl[N(2.6-Me2C6H3)Me]2 have also been synthesized from the reactions of Cp*ZrCl3 with the corresponding lithium anilide. Molecular structures of three complexes were determined by single crystal X-ray diffraction analysis. Upon activation with Al’Bu3 and Ph3CB(C6F5)4. all complexes exhibit good catalytic activity for ethylene polymerization, and produce polyethylene with moderate molecular weight. Complexes of the type Cp*ZrCl2[N(2.6-R21C6H3)R2] also exhibit moderate catalytic activity for copolymerization of ethylene with 1-hexene. and produce copolymers with relatively high molecular weight and reasonable 1-hexene incorporation. We can conclude that the catalytic performance of these complexes for ethylene polymerization as well as ethyl ene/1-hexene copolymerization is notably influenced by the nature of the substituents on the anilide ligands. The low catalytic activity of the bisanilide complex Cp*ZrCl[N(2.6-Me2C6H3)Me]2 for ethylene/1-hexene copolymerization may be caused majorly by the difficult activation process of it in catalyst system. In addition, the activation procedure of these catalyst systems were studied by 1H NMR spectroscopy.In Chapter Four, A number of new half-sandwich zirconium(Ⅳ)(titanium) complexes bearing N, N-dimethylaniline-amido ligands and one half-sandwich titanium(Ⅳ) complexes bearing N, N-dimethylaniline-amido ligands were prepared by reaction of Cp*ZrCl3 with ortho-C6H4(NMe2)CH2NRLi. All of the zirconium complexes were determined by single crystal X-ray diffraction analysis. Upon activation with AliBu3 and Ph3CB(C6F5)4, All complexes exhibit high catalytic activity for ethylene polymerization producing polyethylene with relatively high molecular weight. They also exhibit moderate catalytic activity for copolymerization of ethylene with 1-hexene. producing copolymers with relatively high molecular weight and reasonable 1-hexene incorporation. The polyethylene obtained by titanium complex possessed high molecular molecular, and ethylene-co-1-hexene copolymer obtained by titanium complex possessed high molecular molecular and high 1-hexene incorporationIn Chapter Five, Five zirconium complexes bearing N,N-dimethylaniline-amido ligands were prepared and two of them were determined by single crystal X-ray diffraction analysis. Further investigations on this type of complexes are in progress.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers > Polymerization,polycondensation reaction
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