Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2006. / "May, 2006." Title from electronic dissertation title page (viewed 10/11/2006) Advisor, James L. White; Committee members, Avraam I. Isayev, Thein Kyu, Darrell H. Reneker, Shing-Chung "Josh" Wong; Department Chair, Sadhan C. Jana; Dean of the College, Frank N. Kelley; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

This dissertation explores fundamental aspects of the reaction of group 4 metallocenes with methylaluminoxane (MAO) that lead to active Ziegler-Natta olefin polymerization catalysts. A novel experimental approach is described, in which a unique spectroscopic probe (a fluorinated substituent) is attached to the metallocene ancillary ligands and the metallocene/MAO mixtures are analyzed using 19F NMR spectroscopy. Group 4 metallocene dimethides bearing pentafluorophenyl (C6F5) substituents were synthesized and treated with MAO in benzene-d6. 19F NMR spectroscopic analysis demonstrated reversible methide transfer to form "cation-like" methylmetallocenium methylaluminates. A series of quantitative titration studies showed that fewer than 10% of the aluminum centers in MAO actually participate in the methide transfer process. A systematic study of metallocene substituent effects suggested that MAO contains active centers of extremely high but varying Lewis acidity. Activation of group 4 metallocene dichlorides using MAO was also analyzed using 19F NMR. Initial Cl/CH3 exchange was followed by Cl transfer to aluminum, whereas "normal" subsequent transfer of CH3 from Al to the methylmetallocenium cation was apparently inhibited by the abstracted chloride. Additional studies showed that the 19F NMR probe is sensitive to the interactions of Zr-Cl bonds with simple alkylaluminum species such as Me3Al, Me2AlCl, MeAlCl2, and Et3Al. However, the method was arguably less useful than 1H NMR spectroscopy in following the metathesis of Zr-Cl and Al-R (R = Me, Et) bonds. New methods of preparing methylhalometallocenes were investigated. The reactions of eleven metallocene dimethyls with triphenylmethyl chloride were highly selective (> 95%) with the five most electron-deficient metallocenes studied. Two other examples showed good selectivity on an NMR scale but could not be isolated from the 1,1,1-triphenylethane byproduct. Reactions of dimethylmetallocenes with benzyl bromide were also selective for formation of the corresponding methylbromo-metallocenes, however the reactions were too slow to be of practical value. The observation of long initation periods and the analysis of organic byproduct distributions suggested that these halogenation reactions may proceed by a radical chain mechanism rather than simple sigma bond metathesis. To demonstrate "proof of concept" in the use of 19F NMR to analyze the reactions of paramagnetic metallocenes, the coordination of CO and CN- to C6F5-substituted chromocenes were analyzed. Whereas CO coordinates readily to chromocene, cyanide coordinates effectively to 1,1'-bis(pentafluorophenyl)chromocene. This observation is interpreted in terms of the electron-withdrawing effect of the C6F5 substituent, which should strengthen bonding to sigma-donor ligands (CN-) and weaken bonding to pi-acceptors (CO). / Ph. D.

Three new tetrafluoropyridyl-substituted cyclopentadienes were synthesized. Reactions of pentafluoropyridine (C5F5N) with sodium cyclopentadienide (NaCp) in THF with excess NaH present afforded mixtures of (4-tetrafluoropyridyl)cyclopentadiene (1), 1,3-bis(tetrafluoropyridylcyclopentadiene) (2), and 1,2-bis(tetrafluoropyridylcyclo-pentadiene) (3). Selectivity for mono- and diarylation was controlled by varying the reaction time. Each of the three cyclopentadienes (1, 2, and 3) was converted to its corresponding substituted sodium cyclopentadienide (4, 5, and 6, respectively) by treatment with NaH in THF. Reaction of the monoarylated sodium cyclopentadienide (4) with M(CO)5Br in THF (M = Mn, Re) afforded the corresponding substituted CpM(CO)3 complexes (7Mn and 7Re). The diarylated sodium cyclopentadienides (5 and 6) likewise afforded the diarylated complexes 8Mn, 8Re, 9Mn, and 9Re. Infrared spectroscopic measurements of [(C5F4N)nC5H5-n]M(CO)3 (M = Mn, Re; n = 0 - 2) revealed an increase of about 6 cm-1 in the A-symmetric C-O stretching mode per C5F4N group, which is significantly higher than the average increase (4 cm-1) found earlier for C6F5 groups. Reaction of 2 equiv of 4 with FeBr2 in THF afforded the 1,1'-diarylated ferrocene (10). Analogous reactions starting with 5 and 6 afforded tetraarylated ferrocenes (11 and 12, respectively). Reaction of 2 equiv of 4 with ZrCl4 afforded (C5F4NCp)2ZrCl2 (13), whereas the reaction of CpZrCl3 with 1 equiv of 4 afforded (C5F4NCp)CpZrCl2 (14). Metallocene (13) was found to be moderately active for ethylene/1-hexene copolymerization (1 atm of C2H4, toluene solvent, methylalumoxane cocatalyst). / Master of Science

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: This study concerns the copolymerization of propylene with l-heptene. The percentage of l-heptene used as co-monomer in the polymerization reactions was varied from 5% to 20% in order to compare a variety of polymers with different percentages of comonomer incorporated. A variety of different catalysts were used for these polymerizations. Two metallocene catalysts were used: (A) the isospecific catalyst, rae- [ethylene bis(l-indenyl)]zirconium dichloride (rac-Et(Ind)2ZrCh2) and (B) the silylene-bridged catalyst, rac-Me2Si(2-MeBenz[ e]Ind)zZrCh2. Methylaluminoxane (MAO) was used as cocatalyst for these two metallocene catalysts. Another series of polymerization reactions was done using a Ziegler-Natta catalyst, namely TiCb/AlEt3/Si02. Characterization of the copolymers included usmg high temperature gel permeation chromatography (HTGPC) for molecular mass and molecular mass distributions, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) to investigate the thermal and mechanical properties of the copolymers, nuclear magnetic resonance spectroscopy (NMR) for information concerning the microstructures of the copolymers and crystallization analysis fractionation (CRYSTAF) to investigate the short chain branching of the copolymers. Comparative studies were done on the different catalysts and the polymer properties. The synthesized polymers were also compared with copolymers of propylene with l-hexene and l-octene. / AFRIKAANSE OPSOMMING: Hierdie studie behels die kopolimerisasie van propileen met I-hepteen. Die persentasie van I-hepteen wat as komonomeer in die polimerisasie-reaksies gebruik is, is van 5% tot 20% gevarieer. 'n Verskeidenheid van verskillende kataliste is gebruik vir hierdie polimerisasies. Twee metalloseenkataliste is gebruik: (A) die isospesifieke katalis, rae- [etileen bis(l-indeniel)]zirconium dichloried (rac-Et(lnd)2ZrCh2) en (B) die silileengebrugde katalis, rac-Me2Si(2-MeBenz[e]Ind)2ZrCh2. Metielaluminoksaan (MAO) is as ko-katalis gebruik saam met bogenoemde twee metalloseenkataliste. 'n Ander reeks polimerisasie reaksies is gedoen waarin 'n Ziegler-Natta katalis gebruik is as aktiverende katalis, naamlik TiCi)/ AlEt3/Si02. Die karakterisering van die kopolimere sluit in: hoë temperatuur gel deurlatings chromatrografie (HTGPC) vir molekulêre massa en molekulêre massa verspreidings, differensiële skandering kalorimetrie (DSC) en dinamiese meganiese analisering (DMA) om sodoende die termiese en meganiese eienskappe van die polimere te ondersoek, kern magnetiese resonans spektroskopie (KMR) vir inligting in verband met die mikrostrukture van die kopolimere en kristallisasie analise fraksioneringstegniek (CRYSTAF) om die kort-kettingvertakkings van die kopolimere te ondersoek. Vergelykende studies IS op die verskillende katalisatore en die polimeereienskappe gedoen. Die gesintetiseerde polimere is ook met kopolimere van propileen met I-hekseen en l-okteen vergelyk.

No description available.

Recent advances in polyolefin manufacture have focused on the production of differentiated commodity polyolefins, specialty polyolefins, and polyolefins hybrids. What differentiates these new polyolefin types from commodity polyolefins is that their molecular architectures are much more complex and often contain long chain branches (LCBs), leading to unique properties that make them competitive with specialty polymers. One approach to produce these novel polyolefins is to use one or two single-site catalysts in two CSTRs in series. The first CSTR is used to make semicrystalline polymer chains, some of which must be vinyl-terminated (macromonomers). These macromonomers are then incorporated, via terminal branching, onto the chains growing in the second CSTR, becoming LCBs. If the backbone and the macromonomer have different compositions, they are called cross-products. Since it is not possible to incorporate all macromonomers, the final polymer will consist of a complex mixture of linear chains made by the two catalysts, homogeneous-branched chains (that is, chains where the backbone and all LCBs are of the same type), and cross-product macromolecules. The cross-product will add rather special properties to the polymer and, depending on its molecular architecture, the final product may act as a thermoplastic elastomer (TPE). Developing polymer reactor models for different catalyst combinations can help understand the details of these complex syntheses and to control the properties and fractions of linear chains, homogeneous-branched chains, and cross-products. Two mathematical models were developed in this thesis for the solution polymerization of olefins with two single-site catalysts to predict the microstructure of long chain branched polyolefins. The first model was developed for a semi-batch reactor and the second one for two CSTRs in series. The models can predict the fractions of different polymer populations made in CSTRs and semibatch reactors, as well as their average chain lengths and LCB densities. Simulation results show that CSTRs are more efficient than semi-batch reactors to make polymers with high LCB densities and/or cross product fraction. Simulation results also show that to increase the weight percent of cross-product using a linear-catalyst and a LCB-catalyst, the rate of macromonomer formation of the linear-catalyst should be high. The fraction of cross-product can be increased even further when both catalysts are capable of incorporating macromonomers to form LCB-chains because; in this case, both catalysts can form cross-product chains. Monomer concentration has no effect on cross-product mass fraction and polydispersity index, but increasing monomer concentration will decrease LCB density and increase the average chain lengths. Catalyst deactivation also has a great impact on polymer properties: LCB density, polydispersity index, cross-product fraction, and average chain lengths will all decrease by increasing the catalyst deactivation rate of both catalysts. Simulation results for two CSTRs in series shows that increasing residence time in the second CSTR will lead to higher cross-product formation and LCB density. This rate of increase is more significant if the residence time in the second CSTR is similar to that of the first CSTR. The catalyst feed policy also has a great impact on polymer properties. We found out that feeding the linear-catalyst and the LCB-catalyst in equal amounts to the first CSTR and just adding the LCB-catalyst to the second CSTR is the preferred catalyst injection method for making polymer with a high mass fraction of cross-product, high chain length averages, and lower polydispersity index (PDI). These simulation studies indicate that detailed polymerization kinetics for each catalyst is needed in order to synthesize these novel polyolefins. In the experimental part of this thesis, ethylene polymerization kinetics studies were performed first with two individual metallocene catalysts, then with both of them simultaneously. First, ethylene polymerization with rac-Et(Ind)2ZrCl2/MAO was carried out in a semi-batch solution reactor. Reaction temperature, monomer, MAO, and catalyst concentrations were the factors studied to establish a framework to predict catalyst decay, polymer yield and molecular weight averages. The polymerization order with respect to ethylene and catalyst concentration was found to be first order. Chain transfer to monomer was the dominating chain transfer reaction while β-hydride elimination was negligible. An increase in MAO concentration led to a decrease in molecular weight. Catalyst decay could be described with a first order mechanism. At low MAO concentration this catalyst could make polymer with about one vinyl group per chain. A similar ethylene polymerization kinetics study using dimethylsilyl(N-tert-butylamido)-(tetramethylcyclopentadienyl)-titanium dichloride (CGC-Ti)/MAO system showed that the polymerization order with respect to catalyst concentration was first order, but first order catalyst decay failed to explain catalyst deactivation. The polymerization order with respect to ethylene concentration was not unity for the whole range of ethylene concentration. The trigger mechanism, along with reversible first order activation and deactivation with MAO and first order thermal decay, could explain the effect of time, monomer and catalyst concentration on the rate of polymerization. Decrease in MAO concentration increased the amount of polymer chains with terminal vinyl groups and consequently led to polymers with LCBs. Decreasing monomer concentration at low MAO concentration also led to production of polymer chain with more long chain branching. Ethylene homopolymerization and copolymerization with 1-octene were conducted using combined catalysts system at low and high MAO concentrations. Reactivity ratios were calculated and polymer samples with bimodal MWDs were obtained but no increase in LCB frequency or cross product formation was detected using carbon-13 nuclear magnetic resonance (13C NMR) and high-temperature gel permeation chromatography (GPC) coupled with a viscosity detector. In order to promote the formation of cross-product macromolecules, 1,9-decadiene was copolymerized with ethylene using the Et(Ind)2ZrCl2/MAO to make tailored macromonomers with pendant 1-octenyl branches. The macromonomers ranged from having 1 to 6.5 vinyl groups per chain. These macromonomers were then incorporated into growing ethylene/1-butene or ethylene/1-octene copolymer chains using a titanium-based constrained geometry catalyst (CGC-Ti) to form branch block polymer chains with amorphous main backbone having short chain branch density (SCBD) up to 50 per 1 000 carbon atoms, and high crystalinity long chain branches with SCBD up to 3/1000 C atoms (cross product). Increase in polymerization time or catalyst concentration in the second stage of polymerization was observed to increase the cross-product weight fraction. We also observed that an increase in ethylene pressure during the second stage of polymerization, while 1-butene concentration was constant, favoured the formation of cross product. When 1-octene was used as comonomer in the second stage of polymerization, the presence of more pendant vinyl groups in the macromonomer led to increased long chain branching.

The planar-chiral C2-symmetrical dibromoferrocene derivatives, (S,S,Sp,Sp)-1,1'-dibromo-2,2'-di(2-butyl)ferrocene (88) and (S,S,Sp,Sp)-1,1'-dibromo-2,2'-bis{2-[1-(trimethylsilyl)propyl]} ferrocene (92), were synthesized using the well-established “Ugi’s amine” chemistry. The steric influences of the alkyl groups on ferrocenes 88 and 92 in salt-metathesis reactions were investigated. The reaction of 88 and 92 with iPr2NBCl2 yielded mixtures of bora[1]ferrocenophanes (bora[1]FCPs) 94 and 99 and 1,1'-bis(boryl)ferrocenes 95 and 100 respectively. Ferrocene 92 was expected to yield the highest product ratio of bora[1]FCPs to 1,1' bis(boryl)ferrocenes due to the significant amount of steric bulk on ferrocene from the alkyl groups; however, the product ratio was less than the product ratio obtained for the less bulky ferrocene 88. The product ratios for 88 and 92 were compared to the known product ratios for (Sp,Sp)-1,1'-dibromo-2,2'-di(isopropyl)ferrocene (78) and (Sp,Sp)-1,1'-dibromo-2,2'-di(3-pentyl)ferrocene (79) to determine the effects of the alkyl groups in salt-metathesis reactions. To gain more insight into the effects of the alkyl groups on ferrocenes 88 and 92, a series of conformational analyses of 78, 88, and 92 were performed using density functional theory (DFT) calculations. The DFT calculations aided in the explanation for the unexpectedly low product ratio obtained for ferrocene 92. In efforts to obtain new [1]ruthenocenophanes ([1]RCPs), the synthesis of the ruthenium analog of 78, (Sp,Sp)-1,1'-dibromo-2,2'-di(isopropyl)ruthenocene (105), was attempted. To accomplish this, (R,R)-1,1'-bis(α-N,N-dimethylaminoethyl)ruthenocene (109) was prepared using the same chemistry that was used to prepare its ferrocene analog. However, the synthesis of (R,R,Sp,Sp)-1,1'-dibromo-2,2'-bis(α-N,N-dimethylaminoethyl)ruthenocene (110) via the dilithiation of 109 was unsuccessful. The synthesis of dibromoferrocene derivatives using “Ugi’s amine” chemistry is a long and inflexible process. Therefore, a method to prepare dibromoferrocene derivatives through an alternative synthetic pathway was investigated. The synthesis of (Ss,Ss)-1,1'-bis(p-tolylsulfinyl) ferrocene (118) was accomplished by reacting dilithioferrocene•tmeda with (1R,2S,5R)-(-)-menthyl (SS)-p-tolylsulfinate (117). The diastereoselective dilithiation and subsequent silylation of 118 to obtain (Ss,Ss,Sp,Sp)-2,2'-bis(trimethylsilyl)-1,1'-bis(p-tolylsulfinyl)ferrocene (120) proved to be problematic.

Recent advances in polyolefin manufacture have focused on the production of differentiated commodity polyolefins, specialty polyolefins, and polyolefins hybrids. What differentiates these new polyolefin types from commodity polyolefins is that their molecular architectures are much more complex and often contain long chain branches (LCBs), leading to unique properties that make them competitive with specialty polymers. One approach to produce these novel polyolefins is to use one or two single-site catalysts in two CSTRs in series. The first CSTR is used to make semicrystalline polymer chains, some of which must be vinyl-terminated (macromonomers). These macromonomers are then incorporated, via terminal branching, onto the chains growing in the second CSTR, becoming LCBs. If the backbone and the macromonomer have different compositions, they are called cross-products. Since it is not possible to incorporate all macromonomers, the final polymer will consist of a complex mixture of linear chains made by the two catalysts, homogeneous-branched chains (that is, chains where the backbone and all LCBs are of the same type), and cross-product macromolecules. The cross-product will add rather special properties to the polymer and, depending on its molecular architecture, the final product may act as a thermoplastic elastomer (TPE). Developing polymer reactor models for different catalyst combinations can help understand the details of these complex syntheses and to control the properties and fractions of linear chains, homogeneous-branched chains, and cross-products. Two mathematical models were developed in this thesis for the solution polymerization of olefins with two single-site catalysts to predict the microstructure of long chain branched polyolefins. The first model was developed for a semi-batch reactor and the second one for two CSTRs in series. The models can predict the fractions of different polymer populations made in CSTRs and semibatch reactors, as well as their average chain lengths and LCB densities. Simulation results show that CSTRs are more efficient than semi-batch reactors to make polymers with high LCB densities and/or cross product fraction. Simulation results also show that to increase the weight percent of cross-product using a linear-catalyst and a LCB-catalyst, the rate of macromonomer formation of the linear-catalyst should be high. The fraction of cross-product can be increased even further when both catalysts are capable of incorporating macromonomers to form LCB-chains because; in this case, both catalysts can form cross-product chains. Monomer concentration has no effect on cross-product mass fraction and polydispersity index, but increasing monomer concentration will decrease LCB density and increase the average chain lengths. Catalyst deactivation also has a great impact on polymer properties: LCB density, polydispersity index, cross-product fraction, and average chain lengths will all decrease by increasing the catalyst deactivation rate of both catalysts. Simulation results for two CSTRs in series shows that increasing residence time in the second CSTR will lead to higher cross-product formation and LCB density. This rate of increase is more significant if the residence time in the second CSTR is similar to that of the first CSTR. The catalyst feed policy also has a great impact on polymer properties. We found out that feeding the linear-catalyst and the LCB-catalyst in equal amounts to the first CSTR and just adding the LCB-catalyst to the second CSTR is the preferred catalyst injection method for making polymer with a high mass fraction of cross-product, high chain length averages, and lower polydispersity index (PDI). These simulation studies indicate that detailed polymerization kinetics for each catalyst is needed in order to synthesize these novel polyolefins. In the experimental part of this thesis, ethylene polymerization kinetics studies were performed first with two individual metallocene catalysts, then with both of them simultaneously. First, ethylene polymerization with rac-Et(Ind)2ZrCl2/MAO was carried out in a semi-batch solution reactor. Reaction temperature, monomer, MAO, and catalyst concentrations were the factors studied to establish a framework to predict catalyst decay, polymer yield and molecular weight averages. The polymerization order with respect to ethylene and catalyst concentration was found to be first order. Chain transfer to monomer was the dominating chain transfer reaction while β-hydride elimination was negligible. An increase in MAO concentration led to a decrease in molecular weight. Catalyst decay could be described with a first order mechanism. At low MAO concentration this catalyst could make polymer with about one vinyl group per chain. A similar ethylene polymerization kinetics study using dimethylsilyl(N-tert-butylamido)-(tetramethylcyclopentadienyl)-titanium dichloride (CGC-Ti)/MAO system showed that the polymerization order with respect to catalyst concentration was first order, but first order catalyst decay failed to explain catalyst deactivation. The polymerization order with respect to ethylene concentration was not unity for the whole range of ethylene concentration. The trigger mechanism, along with reversible first order activation and deactivation with MAO and first order thermal decay, could explain the effect of time, monomer and catalyst concentration on the rate of polymerization. Decrease in MAO concentration increased the amount of polymer chains with terminal vinyl groups and consequently led to polymers with LCBs. Decreasing monomer concentration at low MAO concentration also led to production of polymer chain with more long chain branching. Ethylene homopolymerization and copolymerization with 1-octene were conducted using combined catalysts system at low and high MAO concentrations. Reactivity ratios were calculated and polymer samples with bimodal MWDs were obtained but no increase in LCB frequency or cross product formation was detected using carbon-13 nuclear magnetic resonance (13C NMR) and high-temperature gel permeation chromatography (GPC) coupled with a viscosity detector. In order to promote the formation of cross-product macromolecules, 1,9-decadiene was copolymerized with ethylene using the Et(Ind)2ZrCl2/MAO to make tailored macromonomers with pendant 1-octenyl branches. The macromonomers ranged from having 1 to 6.5 vinyl groups per chain. These macromonomers were then incorporated into growing ethylene/1-butene or ethylene/1-octene copolymer chains using a titanium-based constrained geometry catalyst (CGC-Ti) to form branch block polymer chains with amorphous main backbone having short chain branch density (SCBD) up to 50 per 1 000 carbon atoms, and high crystalinity long chain branches with SCBD up to 3/1000 C atoms (cross product). Increase in polymerization time or catalyst concentration in the second stage of polymerization was observed to increase the cross-product weight fraction. We also observed that an increase in ethylene pressure during the second stage of polymerization, while 1-butene concentration was constant, favoured the formation of cross product. When 1-octene was used as comonomer in the second stage of polymerization, the presence of more pendant vinyl groups in the macromonomer led to increased long chain branching.

Zugl.: Erlangen, Nürnberg, Univ., Diss., 2006

Universiẗat, Diss., 2002--Mainz.