The objectives of this thesis are to offer the informations about the characteristics of homogeneous olefin polymerization over various metallocenes activated with methyl aluminoxane and about influences of metallocene structures and polymerization conditions on the polymerization behavior, polymer ...
The objectives of this thesis are to offer the informations about the characteristics of homogeneous olefin polymerization over various metallocenes activated with methyl aluminoxane and about influences of metallocene structures and polymerization conditions on the polymerization behavior, polymer microstructures and physical properties. First, for a determination of the active site concentrations, [$C^*$], the simultaneous kinetics and inhibition method using CO as a catalyst inhibitor were examined. This evaluation method is not exact because MAO-activated alkyl Zr-sites exist in dynamic equilibrium between dormant states and a chain propagating site and because some of CO molecules coordinate even to inactive species. The number of active sites was evaluated on the assumption that two molecules of CO coordinate to each active center. The increase of Al/Zr ratio and temperature increased both the number of active sites and the value of kp for ethylene polymerization over $Cp_2ZrCl_2$/MAO. Especially, a drastic increase of activity is mainly due to much higher value of kp above 2,000 of Al/Zr ratio. A comonomer enhanced drastically the catalytic activity to above ca. ten times for ethylene-propylene copolymerization over $rac-Me_2Si(Ind)_2ZrCl_2/MAO$ system. From the apparent observation this is due to the drastic increase of the propagating rate constant, $k_p$ rather than formation of new active sites by the addition of comonomer. Ethylene copolymerization with higher $\alpha$ -olefins by various metallocene catalysts were examined. Rate profiles of propylene copolymerizations with ethylene were considerably different from that of ethylene copolymerization with propylene over $rac-Me_2Si(Ind)_2ZrCl_2/MAO$ or $rac-Et(Ind)_2ZrCl_2/MAO$. One cause of these phenomena is presumably arising from rheological property of polymerization medium. Propylene copolymerization systems were completely viscous, i.e. the homogeneous liquid phase while ethylene copolymers produced were insoluble in medium. For ethylene copolymerizations with $\alpha$-olefins over $rac-Me_2Si(Ind)_2ZrCl_2$, comonomer enhancement effect on activity was remarkable. Furthermore, reactivity ratios of comonomer were relatively high and the value of ${r_E}\times{r_P}$ is smaller than 1. These results indicate this copolymer have narrow a comonomer distribution. The molecular weight is less decreased by incorporation of comonomer and melting point and crystallinity of copolymer becomes lower than those over the unbridged-metallocenes used. For copolymerizations over hafnocene, $(1,2-(CH_2)_{10}C_5H_3)2HfCl_2$, the activity enhancement effect occurred by addition of comonomer in contrast to that over Zr-centered analogue. In addition, hafnocene incorporated more preferentially propylene comonomer than Zr-analogue. The ethylene polymerizations with one metallocene or two mixed components of metallocenes were performed with the addition of hydrogen and/or the change of polymerization temperature. The molecular weight (MW) and the molecular weight distribution (MWD) of polyethylene (PE) prepared with various metallocene catalysts were investigated. The weight average molecular weight ($M_w$) of PE prepared with $Cp_2TiCl_2/MAO$ was about $4,0\times10^5$, while that of PE with $Cp_2ZrCl_2/MAO$ was about $1,0\times10^5$. The PE of bimodal MWD was obtained with the mixed catalyst of $Cp_2TiCl_2$ and $Cp_2ZrCl_2$. The narrow MWD PE was polymerized by the mixed catalyst of $Cp_2ZrCl_2$ and $Et(ind)_2ZrCl_2$, because each catalyst produced the similar Mw of $1,0\times10^5$. However, the change of temperature during the polymerization with the mixture of $Cp_2ZrCl_2$ and $Et(ind)_2ZrCl_2$ produced the bimodal MWD and increased the PDI (polydispersity index) to 4. ansa-Dichloro-[$o$-phenylenedimethylenebis(($\eta^5$-1-indenyl)] zirconium (1) has been prepared from the reaction of dilithiated bis(1-indenyl)-$o$-xylene with $ZrCl_4$ in tetrahydrofuran. $Rac$-1/$meso$-1 ratio close to 1 is obtained and the diastereomeric complexes have been separated by fractional crystallization. Polymerizations of both ethylene and propylene with $rac$-1 and $meso$-1 in the presence of methylaluminoxane (MAO) as cocatalyst have been examined. In ethylene polymerization, $meso$-1 is more active than $rac$-1, while in propylene polymerization, the latter is much more active than the former. The polymerization data and the stereochemical analysis of the obtained polypropylene (PP) by $^{13}C$ NMR spectroscopy reveal that both the activity of the $rac$-1/MAO catalyst and the stereoregularity of PP are low due to the distortion of catalyst $rac$-1 from the $C_2$ symmetry and the fluxionality of the $ansa$-ligand, which is caused by the four carbon atoms of the rigid $o$-phenylenedimethylene bridge. Higher $\alpha$-olefins were polymerized with $rac$-$Me_2Si(ind)_2ZrCl_2/MAO$ system. The activities of polymerization of $\alpha$-olefin longer than 1-hexene were much smaller than those of ethylene and propylene polymerizations. The weight average molecular weight of poly(high $\alpha$-olefins) were 20,000 $\sim$ 30,000. The microstructure of poly(high $\alpha$-olefins) were analyzed with $^{13}C$ and $^1H$ NMR spectroscopy. From the simple spectra of the polymer, it was estimated that poly(1-hexene) and poly(1-octene) synthesized by the chiral ansa metallocene were very highly stereoregular and regioregular. The vinyllidene and isoalkyl group were observed in the chain end structure of the polymer. These structures might be mainly formed from the chain transfer by ($\beta$-H elimination. A novel unbridged metallocene complex, $(1-TolInd)_2ZrCl_2$ $(Tol = p-C_6H_5CH_3)$ was prepared. $Meso$-like $(1-TolInd)_2ZrCl_2$ afforded a syndiotactic-abundant polypropylene having a short tactic length at low temperatures ($-30^\circ C$). This stereosequence is due either to a weakly chain-end controlled or to a syndiotactic site controlled polymerization with site isomerization. Racemic isomer produced a completely atactic PP even at $-30^\circ C$. Some novel metallocene complexes, ($(1,2-(CH_2)_{10}C_5H_3)_2MCl_2$), (M = Ti, Zr, Hf), and $R_1$(2- or 3-$R_2$(Ind)-1-Cp)$ZrCl_2$ ($R_1$ = bridging group, isopropyl or dimethylsilyl; $R_2$ = p-tolyl) complexes have been characterized for ethylene and propylene polymerization.
The objectives of this thesis are to offer the informations about the characteristics of homogeneous olefin polymerization over various metallocenes activated with methyl aluminoxane and about influences of metallocene structures and polymerization conditions on the polymerization behavior, polymer microstructures and physical properties. First, for a determination of the active site concentrations, [$C^*$], the simultaneous kinetics and inhibition method using CO as a catalyst inhibitor were examined. This evaluation method is not exact because MAO-activated alkyl Zr-sites exist in dynamic equilibrium between dormant states and a chain propagating site and because some of CO molecules coordinate even to inactive species. The number of active sites was evaluated on the assumption that two molecules of CO coordinate to each active center. The increase of Al/Zr ratio and temperature increased both the number of active sites and the value of kp for ethylene polymerization over $Cp_2ZrCl_2$/MAO. Especially, a drastic increase of activity is mainly due to much higher value of kp above 2,000 of Al/Zr ratio. A comonomer enhanced drastically the catalytic activity to above ca. ten times for ethylene-propylene copolymerization over $rac-Me_2Si(Ind)_2ZrCl_2/MAO$ system. From the apparent observation this is due to the drastic increase of the propagating rate constant, $k_p$ rather than formation of new active sites by the addition of comonomer. Ethylene copolymerization with higher $\alpha$ -olefins by various metallocene catalysts were examined. Rate profiles of propylene copolymerizations with ethylene were considerably different from that of ethylene copolymerization with propylene over $rac-Me_2Si(Ind)_2ZrCl_2/MAO$ or $rac-Et(Ind)_2ZrCl_2/MAO$. One cause of these phenomena is presumably arising from rheological property of polymerization medium. Propylene copolymerization systems were completely viscous, i.e. the homogeneous liquid phase while ethylene copolymers produced were insoluble in medium. For ethylene copolymerizations with $\alpha$-olefins over $rac-Me_2Si(Ind)_2ZrCl_2$, comonomer enhancement effect on activity was remarkable. Furthermore, reactivity ratios of comonomer were relatively high and the value of ${r_E}\times{r_P}$ is smaller than 1. These results indicate this copolymer have narrow a comonomer distribution. The molecular weight is less decreased by incorporation of comonomer and melting point and crystallinity of copolymer becomes lower than those over the unbridged-metallocenes used. For copolymerizations over hafnocene, $(1,2-(CH_2)_{10}C_5H_3)2HfCl_2$, the activity enhancement effect occurred by addition of comonomer in contrast to that over Zr-centered analogue. In addition, hafnocene incorporated more preferentially propylene comonomer than Zr-analogue. The ethylene polymerizations with one metallocene or two mixed components of metallocenes were performed with the addition of hydrogen and/or the change of polymerization temperature. The molecular weight (MW) and the molecular weight distribution (MWD) of polyethylene (PE) prepared with various metallocene catalysts were investigated. The weight average molecular weight ($M_w$) of PE prepared with $Cp_2TiCl_2/MAO$ was about $4,0\times10^5$, while that of PE with $Cp_2ZrCl_2/MAO$ was about $1,0\times10^5$. The PE of bimodal MWD was obtained with the mixed catalyst of $Cp_2TiCl_2$ and $Cp_2ZrCl_2$. The narrow MWD PE was polymerized by the mixed catalyst of $Cp_2ZrCl_2$ and $Et(ind)_2ZrCl_2$, because each catalyst produced the similar Mw of $1,0\times10^5$. However, the change of temperature during the polymerization with the mixture of $Cp_2ZrCl_2$ and $Et(ind)_2ZrCl_2$ produced the bimodal MWD and increased the PDI (polydispersity index) to 4. ansa-Dichloro-[$o$-phenylenedimethylenebis(($\eta^5$-1-indenyl)] zirconium (1) has been prepared from the reaction of dilithiated bis(1-indenyl)-$o$-xylene with $ZrCl_4$ in tetrahydrofuran. $Rac$-1/$meso$-1 ratio close to 1 is obtained and the diastereomeric complexes have been separated by fractional crystallization. Polymerizations of both ethylene and propylene with $rac$-1 and $meso$-1 in the presence of methylaluminoxane (MAO) as cocatalyst have been examined. In ethylene polymerization, $meso$-1 is more active than $rac$-1, while in propylene polymerization, the latter is much more active than the former. The polymerization data and the stereochemical analysis of the obtained polypropylene (PP) by $^{13}C$ NMR spectroscopy reveal that both the activity of the $rac$-1/MAO catalyst and the stereoregularity of PP are low due to the distortion of catalyst $rac$-1 from the $C_2$ symmetry and the fluxionality of the $ansa$-ligand, which is caused by the four carbon atoms of the rigid $o$-phenylenedimethylene bridge. Higher $\alpha$-olefins were polymerized with $rac$-$Me_2Si(ind)_2ZrCl_2/MAO$ system. The activities of polymerization of $\alpha$-olefin longer than 1-hexene were much smaller than those of ethylene and propylene polymerizations. The weight average molecular weight of poly(high $\alpha$-olefins) were 20,000 $\sim$ 30,000. The microstructure of poly(high $\alpha$-olefins) were analyzed with $^{13}C$ and $^1H$ NMR spectroscopy. From the simple spectra of the polymer, it was estimated that poly(1-hexene) and poly(1-octene) synthesized by the chiral ansa metallocene were very highly stereoregular and regioregular. The vinyllidene and isoalkyl group were observed in the chain end structure of the polymer. These structures might be mainly formed from the chain transfer by ($\beta$-H elimination. A novel unbridged metallocene complex, $(1-TolInd)_2ZrCl_2$ $(Tol = p-C_6H_5CH_3)$ was prepared. $Meso$-like $(1-TolInd)_2ZrCl_2$ afforded a syndiotactic-abundant polypropylene having a short tactic length at low temperatures ($-30^\circ C$). This stereosequence is due either to a weakly chain-end controlled or to a syndiotactic site controlled polymerization with site isomerization. Racemic isomer produced a completely atactic PP even at $-30^\circ C$. Some novel metallocene complexes, ($(1,2-(CH_2)_{10}C_5H_3)_2MCl_2$), (M = Ti, Zr, Hf), and $R_1$(2- or 3-$R_2$(Ind)-1-Cp)$ZrCl_2$ ($R_1$ = bridging group, isopropyl or dimethylsilyl; $R_2$ = p-tolyl) complexes have been characterized for ethylene and propylene polymerization.
주제어
#Metallocenes Olefin polymerizations The number of active sites CO inhibition methods Ethyllene-propylene copolymer LLDPE Polypropylene
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