To see the other types of publications on this topic, follow the link: Metallocene Catalyst.
Dissertations / Theses on the topic 'Metallocene Catalyst'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Metallocene Catalyst.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Taniguchi, Yoshihide, Kazue Kaneko, Teruyoshi Mizutani, and Mitsugu Ishioka. "Space Charge in Low Density Polyethylene Prepared by Metallocene Catalyst." IEEE, 2001. http://hdl.handle.net/2237/7164.
Full text
2
Alsayary, Omar. "Group 4 and Group 10 post metallocene ethylene polymerization catalysis : catalyst structure-polymer properties relationship." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/group-4-and-group-10-post-metallocene-ethylene-polymerization-catalysis-catalyst-structurepolymer-properties-relationship(ae5d83a2-4e13-4b8c-b7cc-cf7d67667d3d).html.
Full textAbstract:
The new ligand L1 [2-[(E)-2,6-diisopropylphenyl-phenyimino]-2H-acenaphthylen-(1E)-ylidene]-(2,4,6-trimethyl-phenyl)-amine was prepared by stepwise addition of 2,6-diisopropylaniline and 2,4,6 trimethylaniline to acenaphthenequinone. The L1NiBr2 complex crystallized as a pseudo tetrahedral monomer, as determined by single crystal X-ray diffraction. This new catalyst L1NiBr2 and 3 related catalysts, bis(2,6-diisopropylphenyl)acenaphthenediimineNiBr2 (L2NiBr2), [(N,N'-bis-(2,6-diisopropylphenyl)-phenanthrene-9,10-diylidendiamineNi-η3-C3H4COOCH3)]+.{B[C6H3(CF3)2]4-} [(L3Ni-η3-C3H4COOCH3)]+.{B[C6H3(CF3)2]4-} and N-(2,6-diisopropylphenyl)-N'-(2,4,6-trimethylphenyl)-phenanthrene-9,10-diylidenediamineNiBr2 (L4NiBr2) were tested for activity in ethylene polymerization. The super-bulky α-diimine nickel catalysts [(η3- L3NiC3H4COOCH3)]+.{B[C6H3(CF3)2]4-} and L4NiBr2 successfully produced higher molecular weight polyethylene with a high level of linearity compared to the less bulky α-diimine nickel catalysts (L1NiBr2 and L2NiBr2). The super bulky α-diimine backbone helped to compress the reaction space and therefore impede the ethylene insertion to active centre of the catalyst. For this reason, the catalyst activity for super- bulky backbone ligands (L3 and L4) is lower than for their analogous less-bulky backbone ligands (L1 and L2). In general, for both backbones, the nickel catalysts with all-isopropyl substituents produced higher molecular weight polyethylene with less linearity compared to the nickel catalysts with methyl substituents. Moreover, for the acenaphthene backbone, the nickel catalysts with all isopropyl substituents (L2NiBr2) got a higher activity compared to the nickel catalysts with methyl substituents (L1NiBr2). A similar catalyst activity trend was not observed for phenanthrene backboned catalysts. In contrast, L4NiBr2 showed a higher activity compared to [(η3- L3NiC3H4COOCH3)]+.{B[C6H3(CF3)2]4-} For all catalysts, the majority of branches, as characterized by 13C nuclear magnetic resonance, were methyl branches. Polymers with a high level of branches showed a sharp intensity in the loss modulus measured by dynamic mechanical analysis due to a high level of interfacial chains. A reduction in catalyst activity was observed with all nickel catalysts when supported on silica. However, supporting nickel catalysts helps to improve the linearity of the polymer. The same ligands L3 and L4 were used with palladium and successfully produced two new catalysts [L3PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} and [L4PdCH3NCCH3]+.{B[C6H3(CF3)2]4-. Catalyst [L3PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} was more active and produced higher molecular weight and less branched polymer than catalyst [L4PdCH3NCCH3]+.{B[C6H3(CF3)2]4-} in the polymerization of ethylene.
3
Beigzadeh, Daryoosh. "Long-chain branching in ethylene polymerization using combined metallocene catalyst systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/NQ52024.pdf.
Full text
4
Kojo, Shinichi. "Studies on Propylene Polymerization with MgCl_2-Supported TiCl_4 and Metallocene Catalyst Systems." Kyoto University, 1999. http://hdl.handle.net/2433/181329.
Full text
5
Kaneko, K., H. Semi, T. Mizutani, T. Mori, and M. Ishioka. "Charge Transport and Space Charge Formation in Low-Density Polyethylene." IEEE, 2000. http://hdl.handle.net/2237/7177.
Full text
6
Charpentier, Paul A. "Metallocene-catalyzed semi-batch and continuous polymerization of ethylene /." *McMaster only, 1997.
Find full text
7
Abdelbagi, Mohamed Elnaiem Mohamed [Verfasser], and Helmut G. [Akademischer Betreuer] Alt. "Synthesis of Bridged and Unbridged Group (lV) Metallocene Complexes as Catalyst Precursors for Ethylene Polymerization / Mohamed Elnaiem Mohamed Abdelbagi. Betreuer: Helmut G. Alt." Bayreuth : Universität Bayreuth, 2011. http://d-nb.info/1059413493/34.
Full text
8
Mäkelä-Vaarne, Nora. "Characterisation of group 4 metallocenes and metallocene catalysts : UV/VIS spectroscopic study." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/kemia/vk/makela-vaarne/.
Full text
9
Theurkauff, Gabriel. "Investigations on the stereoselective polymerization of α-olefins by single-site group IV metal catalysts." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S158/document.
Full textAbstract:
Les travaux présentés dans ce manuscrit ont trait à la catalyse de polymérisation des α-oléfines sont présentés en 4 parties distinctes. La première est consacrée à l'étude d'un système catalytique pour la production de polypropylène élastomère. L'analyse poussée des polymères produits et la caractérisation complète des catalyseurs utilisés a permis de montrer la présence de deux homopolymères sous forme de blende. La seconde partie porte sur la copolymérisation de monomères bifonctionnels vinyl-vinylidène avec le propylène. La caractérisation des polymères a permis de révéler la réactivité particulière des liaisons vinylidène et d'étudier l'influence du catalyseur utilisé sur le mécanisme de la polymérisation. La troisième partie s'intéresse à la caractérisation des espèces active en polymérisation et à l'étude des mécanismes d'activation et de désactivation des catalyseurs métallocènes. La synthèse et la caractérisation d'espèces cationiques, l'étude de leur comportement dynamique en solution, ainsi que l'évaluation de leur productivité en polymérisation ont permis d'établir un lien entre les propriétés électrophiles de ces espèces et de leur activité en polymérisation. La dernière partie porte sur l'homopolymérisation d'α-oléfines encombrées. La recherche d'un catalyseur suffisamment productif nous a amené à tester plusieurs catalyseurs présentant des structures différentes. L'absence de catalyseur productif soulève l'hypothèse d'interactions désactivantes entre le catalyseur et le monomèreThe work presented in the manuscript focus on α-olefin polymerization catalysis, and is divided into four distinct parts. The first part is dedicated to the study of catalytic systems for the production of elastomeric polypropylene. The analysis of the produced polymers and the characterization of the catalysts showed the presence of two homopolymers as a blend in the elastomeric polypropylene. The second part focuses on the copolymerization of bifunctionnal vinyl-vinylidene monomers with propylene. The characterization of the polymers revealed the reactivity of the vinylidène bonds and showed different polymerization mechanisms for the different catalysts. The third part reports a study on the activation and deactivation pathways of the active species in polymerization. The characterization of model cationic species and the study of their behavior in solution and in polymerization showed the relationship between the electrophilicity of the species and its productivity in propylene polymerization. The last part is dedicated to the polymerization of hindered α-olefins. The quest for a productive catalyst led to test various single site catalysts with different structures. Deactivating interactions between the monomers and the catalyst are supposed to explain the low productivity of the tested catalysts
10
Diamond, Gary M. "ANSA-bridged and binuclear metallocene compounds of zirconium and hafnium." Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:297bc125-5270-4969-89c3-69fd326e5c02.
Full textAbstract:
This thesis describes the synthesis and characterisation of new mononuclear and binuclear zirconium and hafnium compounds containing ansa-bridged ligands. Some olefin polymerization studies, employing the new compounds as catalysts, are also presented. Chapter 1 begins with an introduction to Ziegler-Natta polymerization of olefins, concentrating on recently developed metallocene-based catalyst systems. The second part of the Chapter charts the development of group 4 ansa-metallocene derivatives, especially their use as stereospecific catalysts. Finally, a review of binuciear group 4 metallocene compounds containing bridging bis(cyclopentadienyl)-type ligands is presented. Chapter 2 describes the synthesis and characterisation of some novel mononuclear metallocene compounds of zirconium and hafnium containing ansa-bridged ligands. The ansa-bridged mononuclear compounds [{Me2C(η5-C5H4)(η2-C9H6)}M(η5C5H5)Cl] (M = Zr, Hf), [{(CH2)5C(η5-C5H4)(η2-C9H6)}M(η5-C5H5)Cl] (M = Zr, Hf) and [{Me2(η5-C5H4)(η3-C13H8)}Zr(η5-C5H5)Cl] are described, along with the X-ray crystal structures of the zirconium compounds. The η2-indenyl and η3-fluorenyl coordination modes observed for these compounds are unprecedented. The synthesis and characterisation of the novel, mononuclear ansa-bridged compounds [{Me2C(η5-C5H4)
11
Laur, Eva. "Rare-earth metallocene complexes for syndioselective styrene (co)polymerization." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S168.
Full textAbstract:
Les travaux présentés dans ce manuscrit portent sur la (co)polymérisation syndiosélective du styrène catalysée par des complexes de métaux du Groupe 3. La première partie est consacrée à l’optimisation des performances catalytiques de systèmes neutres de type {Cp/Flu}. Une série de précurseurs ansa-lanthanidocènes a été synthétisée et testée en homopolymérisation du styrène et en copolymérisation styrène-éthylène. Il a été montré que la nature de la substitution du motif fluorényle, la nature du centre métallique ainsi que les conditions de polymérisation ont une influence significative sur la productivité des catalyseurs. En conditions optimisées, des productivités maximales de 4,500 kg(sPS)·mol⁻¹·h⁻¹ et 5,430 kg(sPSE)·mol⁻¹·h⁻¹ ont été obtenues, démontrant la robustesse sans précédent de ces systèmes catalytiques en conditions extrêmes (Tpolym jusqu’à 140 °C et charge en monomère > 100,000). De nouveaux co- et terpolymères styrène-myrcène et styrène-myrcène-éthylène contenant des séquences de polystyrène syndiotactique ont également été synthétisés. La deuxième partie de ce travail porte sur le développement de nouveaux catalyseurs cationiques. Très peu des composés ciblés ont été isolés de par la réactivité déroutante entre les pro-ligands et les précurseurs ou la faible stabilité thermodynamique des produits. De plus, les productivités catalytiques des composés qui ont été isolés se sont avérées assez faiblesThe work presented in this thesis manuscript focuses on the syndioselective (co)polymerization of styrene catalyzed by Group 3 catalysts. The first part is dedicated to the optimization of the catalytic performances of neutral {Cp/Flu} systems. A series of new allyl ansa-lanthanidocenes was synthesized and explored in styrene and styrene-ethylene (co)polymerizations. It is shown that the substitution of the fluorenyl moiety as well as the nature of the metal center and the polymerization conditions exert a strong influence on the catalyst productivity. Under optimized conditions, maximum productivities of up to 4,500 kg(sPS)·mol⁻¹·h⁻¹ and 5,430 kg(sPSE)·mol⁻¹·h⁻¹ were achieved, highlighting the unprecedented robustness of those catalytic systems under drastic conditions (Tpolym up to 140 °C and monomer : catalyst ratios > 100,000). New styrene-myrcene(-ethylene) co- and terpolymers containing syndiotactic polystyrene sequences were also synthesized. The second part of the study was focused on the development of new cationic catalysts. Only a short series of compounds was successfully isolated among the targeted ones, because of unclear reactivity of pro-ligands and metal precursors and/or low thermodynamic stability of the products. The new isolated compounds were also used in styrene homopolymerization affording unexpectedly poor performances
12
Yang, Minghua. "Silica supported metallocene catalysts and olefin polymerization." Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488443.
Full text
13
Nguyen, Huy Van. "Metallocene-Pyrrolidinopyridine Nucleophilic Catalysts for 1.V." Thesis, Queen Mary, University of London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498184.
Full text
14
Endeward, Burkhard, Marcelino Bernardo, Hans Thomann, and P. Brandt. "Ionic aggregation in metallocene olefin polymerization catalysts." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194837.
Full text
15
Popham, Neil Andrew. "Studies on binuclear ansa-metallocene transition metal complexes." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318628.
Full text
16
Soltan, Omar. "Solution isomerization of commercial C₂-symmetric metallocene catalysts /." Link to the online version, 2006. http://hdl.handle.net/10019/1219.
Full text
17
Abdel-Hadi, Emad Hussein. "Supported post-metallocene catalysts systems for olefin polymerization." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529231.
Full text
18
Soltan, Omar. "Solution isomerization of commercial C2-symmetric metallocene catalysts." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2856.
Full textAbstract:
Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006.This study concerns the investigation of the isomerization of different metallocene catalysts in solution, and the effects thereof on the microstructure of polypropylenes prepared with these catalysts. Two C2 symmetric ansa metallocenes, ethylene-bis(indenyl) zirconium dichloride (EI) and dimethylsilyl-bis(2-methyl benzoindenyl) zirconium dichloride (MBI) were exposed, in solution, to both sunlight and UV radiation. The rac-meso isomerization of these catalysts were followed by 1H NMR spectroscopy. The reaching of a photostationary state is described, as well as the effect of isomerization of these catalysts in solution on the polymerization of propylene. Results show that metallocene structure has an effect on the isomerization rate and photostationary state. Results also show that the wavelength of light plays a role in the isomerization process. Effects on stereochemistry and molecular weight of the formed polymer as well as the catalyst activity is described and discussed. In addition the effect of activating the catalysts with MAO before exposure to light is discussed.
19
Monterio, Mario G. Kool. "Polymerization Studies using homogeneous and supported metallocene catalysts." Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642948.
Full textAbstract:
A literature survey of the main aspects of the polymerization of olefins using homogeneous and silica, alumina and niobia supported metallocene catalyst systems is presented. Fundamental information about the surface of niobia and its use as a catalyst support is included. A study of kinetics of polymerization of ethylene was conducted using homogeneous bis(cyclopentadienyl)zirconium dichloride-MAO catalyst systems and its silica, alumina and niobia supported analogue catalyst systems. The characterization of the polyethylene produced by such catalyst systems, focussing on the molecular weight distribution, melting behaviour and morphology of the polymer was carried out.
20
Cobzaru, Cecilia. "Asymmetric metallocene catalysts: design of ultrahigh molecular weight polypropylene plastomers." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-55721.
Full text
21
Holden, Gavin. "Cross-linking of polyethylene and ethylene/ #alpha#-olefin copolymers, initiated by dicumyl peroxide : a study of new polymers and the effects of molecular structure." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322818.
Full text
22
Jang, Yong-Jun. "Nanosized polymer carriers for metallocene catalysts in heterogeneous olefin polymerization." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976096374.
Full text
23
Price, Craig Justin. "Structure-activity relationships in olefin polymerization catalysts." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1678.
Full text
24
Lutz, Marietjie. "Metallocene and Ziegler-Natta catalyzed polypropylene utilizing 1-heptene." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52334.
Full textAbstract:
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.
25
Yeamine, Mehbuba Rukni. "Synthesis ans Application of Planar Chiral Colbat Metallocene Based Palladacycle Catalysts." Thesis, University of East Anglia, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518358.
Full text
26
Endeward, Burkhard, Marcelino Bernardo, Hans Thomann, and P. Brandt. "Ionic aggregation in metallocene olefin polymerization catalysts: a PFG NMR study." Diffusion fundamentals 3 (2005) 19, S. 1, 2005. https://ul.qucosa.de/id/qucosa%3A14310.
Full text
27
Bell, Jane Louise. "The synthesis and applications of chiral, group IV metallocenes." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336625.
Full text
28
Walker, S. E. M. "The structure and performance of injection moulded metallocene catalysed polyethylenes." Thesis, Queen's University Belfast, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273128.
Full text
29
Hair, Gregory Scott. "Synthesis, structure and reactivity of group 13 Lewis acids and group 4 metallocene zwitterions /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
30
Al-Bahily, Khalid A. "Design and synthesis of new C1 and C2-symmetric ansa-metallocene catalysts for isotactic-polypropylene formation." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3061.
Full textAbstract:
Several ansa C1-symmetric cyclopentadienyl-fluorenyl metallocenes based on
zirconium have been prepared with different substituents at position 3 on the
cyclopentadienyl ring. Isotactic polypropylene production from these systems depends
highly on the size of these substituents. Therefore, large groups such as 1-methyl-4-tbutylcyclohexyl
(metallocene 6), 1-methyl-cyclohexyl (metallocene 7), 1,3,3,5-
tetramethylcyclohexyl (metallocene 8), and 2,3,4-trimethyl-3-pentyl (metallocene 9)
have been investigated. In combination with methylaluminoxane (MAO), they showed
good activity and produced high molecular weight of isotactic polypropylene. In terms
of the tacticity of the polymers, metallocene 6 made the best isotactic polypropylene
with ~88% mmmm pentad content. Also, it has been found that if the size of this
substituent is large as in 2,3,4-trimethyl-3-pentyl (metallocene 9), then it will block the
polymerization active site which will deactivate the metallocene.
New synthetic pathways for the synthesis of cyclopentadienyl-fluorenyl
metallocenes based on titanium have been achieved. Anchoring these types of ligands
onto titanium by following the conventional method of using TiCl4 in the metallation
step has failed for the production of Me2C(3-(diphenylmethyl)-C5H3)(C13H8)TiCl2
(metallocene 12), Ph2C(C5H4)(C13H8)TiCl2 (metallocene 14), and
Ph2C(C5H4)(C13H8)TiMe2 (metallocene 15); this is possibly due to the high reactivity of
TiCl4. Therefore, TiCl4·2THF has been prepared and used in that step to produce these
new titanocenes with good yields.
A new ansa-C2-symmetric substituted bis-indenyl metallocene for isotactic
polypropylene production has been successfully prepared. It is known that ansa-C2-
symmetric metallocenes are good catalysts for isotactic polypropylene production, but in
general, their synthesis suffers from the production of the meso Cs-stereoisomer of these
catalysts, which generally produces only atactic polypropylene. Therefore, the meso
stereoisomers must be removed and this is considered a loss of the material that
increases the cost of the catalysts. Addition of bulky substituents on the indenyl groups
as in Me2Si(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenz(f)indenyl)2ZrCl2 (metallocene 5)
has prevented the meso stereoisomer production. 5/MAO produces isotactic
polypropylene with up to ~80% mmmm pentad content.
31
Rodriguez-Delgado, Antonio. "Homogeneous 1-alkene polymerisation catalysts : understanding metallocenes and exploring alternatives." Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268577.
Full textAbstract:
The optimisation of I-alkene polymerisation processes by highly active metallocene systems such as racSBIZrMe2 activated by [Ph3C][CN{B(C6Fs)3h] (I) or by [Ph3C][B(C~s)4] (II) was perfonned. Subsequently. a systematic quantitative study of ligand effects on polymerisation activity, molecular weight and polymer microstructure was carried out. Non-bridged and bridged C2y-symmetry zirconocene dimethyls and dichlorides alkylated (or alkyl exchanged) by AlBu'3 (TIBA) and activated by 1 are much less active than Crsymmetric zirconocenes. Propene polymerisations catalysed by those systems afford low molecular weight atactic polypropene. TIBA rapidly alkylates dichloride zirconocenes affording pre-catalysts which, once activated, give a catalytic profile comparable with that obtained with dimethyl zirconocenes. Activities of Crsymmetry raczirconocenes / AlBui3 / I or [Ph3C][H2N{B(C6Fs)3h] (III) in propene polymerisation decrease according to the order SBMbiZrCh (17) > SBIZrCh (16) > EBIZrCh (13) > MBBIZrCh (18) > EBIDMZrCh (19) > EBTHIZrCb (20) > SBSCZrCh (14) > SBBCZrCh (15). These values are not distorted by side effects such as mass transport limitation, so represent real activities, which are the highest reported to date for most of these catalysts under the experimental conditions fixed. The molecular weight of polypropene obtained in propene polymerisation reactions at 1 bar monomer pressure and 20°C ranges from high to low molecular weight (336000 to 4600 g/mol), decreasing according to the precatalyst, in the following order: SBMbiZrCh (17) > SBIZrCh (16) > MBBIZrCh (18) > EBIZrCh (13) > EBTHIZrCh (20) > SBsczrCh (14) > EBIDMZrCh (19) > SBBCZrCh (15). Experiments carried out at 1 bar of monomer pressure and 60°C afford polymers of medium to low molecular weight and the same trend. The order of isotacticity and regiospecificity of the polypropene obtained is: SBMbiZrCh (17) > SBSCZrCh (14) > SBBCZrCh (15) > MBBIZrCh (18) >EBIZrCh (13) > EBDMIZrCh (19) The trityl salt 1 generates more active catalysts than III for the polymerisations perfonned at 20°C, but the situation is reversed at 60 0c. The molecular weight of the polymers obtained by systems activated by III is slightly higher than those obtained using I under both experimental regimes (20 and 60°C / 1 bar). Reactions of L2ZrMe2 (where 4, L= CsMes; 6, L= CSMe4H) with III in presence of AIMe3, fonn [(~)Zr(JlMe) 2AIMe2][H2N{B(C6Fs)3h] (23, L= CsMes; 24, L= CSMe4H) whereas with I, ~ZrMe(Il-Me)B-(C6F5h and L2ZrMe(Il-NC)B-(C6FS)3 were obtained. The protolysis reaction ofY[N(SiMe3)2h with (2-C~sN=CH)(6-Bu)C6H30H (HL3 ) led to a variety of products. Y[N(SiMe3)2h(L3) (29), alongside Y[N(SiMe3)2](L3)2 (30) and Y(L3h (31) were synthesised. M(CH2SiMe3)2(THF)(Ll) (25, M = Sc; 26, M = Y; and L 1 = 2,3,6-Me3C6H3N=CH(6-Bu')C~30H) are highly effective catalysts for the ring-opening polymerisation of E-caprolactone. 26 and 30 also initiate polymerisation of cyc10hexene oxide (CHO).
32
Dai, Shuanghua Patrick. "X-ray scattering and thermal analysis study of isotactic polypropylene /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2000.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2000.Submitted to the Dept. of Physics. Adviser: Peggy Cebe. Includes bibliographical references (leaves 246-251). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
33
Lancaster, Simon John. "Synthesis, structure and catalytic activity of cationic zirconium and hafnium alkyl complexes." Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297046.
Full text
34
Abedalrazek, Eyad Waleed. "Developing New Supports for Metallocene Catalysts and their Effects on Ethylene Polymerization." Thesis, University of Manchester, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525977.
Full text
35
Gupta, Pankaj. "Processing-Structure-Property Studies of: I) Submicron Polymeric Fibers Produced By Electrospinning and II) Films Of Linear Low Density Polyethylenes As Influenced By The Short Chain Branch Length In Copolymers Of Ethylene/1-Butene, Ethylene/1-Hexene & Ethylene/1-Octene Synthesized By A Single Site Metallocene Catalyst." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/30090.
Full textAbstract:
The overall theme of the research discussed in this dissertation has been to explore processing-structure-property relationships for submicron polymeric fibers produced by electrospinning (Part I) and to ascertain whether or not the length of the short chain branch has any effect on the physical properties of films of linear low-density polyethylenes (LLDPEs) (Part II). Electrospinning is a unique process to produce submicron fibers (as thin as 100 nm) that have a diameter at least two orders of magnitude smaller than the conventional fiber spinning processes based on melt and solution spinning. As a result, the electrospun fibers have a very high specific surface. The research efforts discussed in Part I of this dissertation relate to some fundamental as well as more applied investigations involving electrospinning. These include investigating the effects of solution rheology on fiber formation and developing novel methodologies to fabricate polymeric mats comprising of high specific surface submicron fibers of more than one polymer, high chemical resistant substrates produced by in situ photo crosslinking during electrospinning, superparamagnetic flexible substrates by electrospinning a solution of an elastomeric polymer containing ferrite nanoparticles of Mn-Zn-Ni and substrates for filtration applications. More specifically, it was found that the solution rheological parameters like concentration and viscosity, in addition to molecular weight play an important role in governing the fiber formation during electrospinning of polymer solutions. Furthermore, it was found that fiber formation depends strongly on the solution concentration regime, i.e., at low and dilute concentrations, droplets and beaded fibers were formed whereas uniform fibers were observed to form at a solution concentration greater than at least six times than that of the critical chain overlap concentration, c*, for linear homopolymers of poly(methyl methacrylate) that had molecular weight distributions ranging from 1.03-1.35 (Mw/Mn). In contrast, uniform fibers were observed at ten times the value of c* for the relatively broader molecular weight polymers (Mw/Mn~1.6-2.1). Novel methodologies were developed to in situ photocrosslink the electrospun jet to produce a crosslinked network in the form of a submicron fiber that could potentially be utilized for applications where a high resistance to chemical environments is required. In addition, flexible superparamagnetic substrates were developed by electrospinning a solution of an elastomeric polymer containing magnetic nanoparticles based on "mixed" ferrites of Mn-Zn-Ni where the specific saturation magnetization and the magnetic permeability of these substrates were found to increase linearly with the wt% loading of the nanoparticles. The methodology to simultaneously electrospin two polymer solutions in a side-by-side fashion was developed to produce bicomponent fibers with the rationale that the resulting electrospun mat will have properties from a combination from each of the polymer components. Bicomponent electrospinning of poly(vinyl chloride)- polyurethane and poly(vinylidiene fluoride)-polyurethane was successfully performed. In addition, filtration properties of single and bicomponent electrospun mats of polyacrylonitrile and polystyrene were investigated. Results indicated lower aerosol penetration or higher filtration efficiencies of the filters based on submicron electrospun fibers in comparison to the conventional filter materials.
In addition, Part II of this dissertation explores whether or not the length of the short chain branch affects the physical properties of blown and compression molded films of LLDPEs that were synthesized by a single site metallocene catalyst. Here, three resins based on copolymers of ethylene/1-butene, ethylene/1-hexene, and ethylene/1-octene were utilized that were very similar in terms of their molecular weight and distribution, melt rheology, density, crystallinity and short chain branching content and its distribution. Interestingly, at higher deformation rates (ca. 1m/s), the breaking, tear and impact strengths of films based on ethylene/1-hexene and ethylene/1-octene were found to be superior than those based on ethylene/1-butene. While the origin of these differences in mechanical properties with increasing short chain branch length was not fully understood, the present investigation did confirm this effect to be pronounced only at high deformation rates for both the blown and compression molded LLDPE films.Ph. D.
36
Rodrigues, Anne-Sophie. "Group 3 allyl ansa-metallocene complexes for styrene (co)polymerization catalysis." Rennes 1, 2007. http://www.theses.fr/2007REN1S063.
Full textAbstract:
A family of new group 3 and lanthanides allyl ansa-metallocene complexes has been synthesized and characterized by NMR and X-ray diffraction. The performances of these discrete single-component catalysts for styrene homo- and copolymerization have been studied. The bridged cyclopentadienyl-fluorenyl complexes exhibited a good control and high stereoselectivity for the production of syndiotactic polystyrene, while bridged bis(indenyl) complexes produced highly isotactic polystyrene. The influence of the complex structure on activity and selectivity is highlighted. Besides, these catalysts allowed the synthesis of new, original polymer materials via copolymerisation of styrene with ethylene and/or isoprene. Some thermal and mechanical properties of those styrene-rich copolymers have been evaluated and suggest promising applicationsUne famille de nouveaux complexes allyles ansa-métallocènes du groupe 3 et des lanthanides a été synthétisée et caractérisée par RMN et diffraction des rayons X. Les performances des ces catalyseurs mono-sites en homo- et copolymérisation du styrène ont été étudiées. Les complexes cyclopentadiényle-fluorényle ont démontré un bon contrôle et une très haute stéréosélectivité pour la production de polystyrène syndiotactique alors que les complexes bis(indényles) produisent eux du polystyrène hautement isotactique. L’influence de la structure de ces complexes sur l’activité et la sélectivité a ainsi été mise en évidence. D’autre part, ces catalyseurs ont permis la synthèse de nouveaux matériaux polymères originaux par copolymérisation du styrène avec de l’éthylène et/ou de l’isoprène. Quelques propriétés thermiques et mécaniques de ces copolymères riches en styrène ont été évaluées et suggèrent des applications prometteuses
37
Bonnin, Quentin. "New cationic group 4 metallocenes as potential organometallic frustrated Lewis pairs : synthesis, reactivity and catalysis." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK031.
Full textAbstract:
Le concept de “paires frustrées de Lewis” (plus communément désignés par l’acronyme anglais FLPs) a suscité un vif intérêt depuis sa formulation en 2006. Initialement décrit à partir d’une phosphine encombrée comme base de Lewis et d’un borane comme acide de Lewis pour l’activation coopérative d’hydrogène sans métal, ce concept a été ensuite très largement développé en utilisant divers éléments du groupe principal (N/B, P/Al, N/Al …). Le concept a ensuite été étendu aux métaux de transitions pour pallier cette faiblesse: sont ainsi apparues les premières paires frustrées de Lewis organométalliques (OmFLPs). Dans le but de développer de telles OmFLPs, nous nous sommes intéressés à la synthèse de complexes cationiques titanocèniques et zirconocèniques en présence d’une amine. La première partie de cette thèse présente les travaux précédemment décrits sur les ligands azotés, en vue de synthétiser des complexes du groupe 4 N-fonctionnalisés. Une description plus détaillée du concept de FLP est ensuite réalisée, et un parallèle est fait avec des concepts connexes (coopérativité métal-ligand, systèmes ambiphiles). La seconde partie de ce manuscrit développe la synthèse de nouveaux ligands (aminomethyl)cyclopentadiènylure de potassium ainsi qu’une étude de leur coordination aux métaux du groupe 4. Cette étude a permis d’accéder à toute une série de nouveaux complexes dichlorotitanocènes et zirconocènes porteurs d’une fonction amine tertiaire encombrée (diisopropylaminyl et 2,2,6,6-tétraméthylpipéridine) à proximité du centre métallique. Ces travaux ont montré que l’amine ne se coordine pas audit centre métallique. Les métallocènes ainsi formés ont ensuite été transformés en cation afin de renforcer le caractère acidité de Lewis du centre métallique. Ces espèces ont montré une réactivité inattendue donnant lieu à des réarrangements par activation CH au voisinage de l’atome d’azote. Ces réarrangements ainsi que des études mécanistiques font l’objet du troisième chapitre. La quatrième partie de ce mémoire porte sur la synthèse de complexes phosphido- et amidotitanocènes cationiques. Ces complexes montrent une très bonne activité en catalyse d’hydrogénation de petites molécules dans des conditions relativement douces, vraisemblablement pour des raisons d’effets coopératifs entre le métal et le ligand. Dans une dernière partie, la synthèse de complexes titanocéniques cationiques portant une fonction iminophosphorane est développée, suivie d’une étude de réactivité de ces complexes en tant que paires frustrées de Lewis organométalliquesIn 2006, the concept of “frustrated Lewis pairs” (called FLPs) was introduced. The main characteristic of these compounds is their ability to activate cooperatively small molecules without the use of a metal (H2, CO2, alkene alkyne…). Initially based on P/B combination, the concept has been extended to several other main group elements (N/B, P/Al, N/Al …). Recently, FLPs have been extended to the transition metal realm. These organometallic FLPs (OmFLPs) are obviously non-metal free systems but they extend significantly the scope of FLP applications. Seeking to develop such systems, a research toward new omFLP combinations (N/Ti+, N/Zr+) has been initiated in our group, based on the synthesis of N-based titanocene and zirconocene complexes. The first part of this manuscript deals with a survey of the literature of such compounds, and a more detailed presentation of FLPs and related concepts (metal-ligand cooperativity, ambiphilic ligands) are also developed. In a second chapter, the synthesis of new N-based cyclopentadienyl ligands and their coordination to group 4 metals is presented. The formation of a cationic complex is then developed in a third part on selected titanocenes. In these complexes, the amine function undergoes CH activation by the cationic metal centre, leading to unexpected rearrangements. Investigations on their plausible mechanism are also presented. In a fourth part, the synthesis of new cationic phosphido- and amidotitanocenes, discovered in the course of our study on OmFLPs, is developed. The cationic amidotitanocenes are shown to be catalytically active towards hydrogenation of small molecules. Lastly, the potential of cationic titanocenyl iminophosphoranes as OmFLPs, was developed
38
Luruli, Nyambeni. "Synthesis and characterization of homo- and copolymers of a-olefins using metallocene catalysts." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/53077.
Full textAbstract:
Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: This study comprises the synthesis and characterization of propene/lower a-olefin copolymers and a-olefm homopolymers using metallocene catalyst systems. Incorporation of a-olefin comonomer into the polypropene backbone led to a change in properties such as microstructure and melting and crystallization temperatures. Synthesis of propene/a-olefin (J-butene, l-pentene, l-hexene and 4-menthyl-l-pentene) copolymers was carried out using the Me2Si(2-Methylbenz[e]indenyl)2ZrChIMAO catalyst combination. Copolymers were characterized by NMR, GPC, DSC and CRYSTAF. Comonomer incorporation was generally kept below 6 % to ensure crystallizable copolymers. Comonomer content influences tacticity. It was especially pronounced for propenell-butene copolymers and attributed to the formation of clusters. Melting and crystallization temperatures, (Tm (DSC), Tc (DSC) and Tc (CRYSTAF)), of propene/lower a-olefin copolymers decreased linearly with an increase in comonomer incorporation and strongly depend on comonomer type displaying a different behaviour compared to that of propene/ higher a-olefins (l-octene, I-decene, l-tetradecene, and 1- octadecene) copolymers. The melting and crystallization temperatures of propene/4- methyl-l-pentene copolymers occur between those ofpropene/l-pentene and propenellhexene. Poly-n-olefins (l-pentene, l-hexene, l-octene and l-decene) were prepared using a series of (R-115_C9H6)2ZrChIMAO[R = benzyl, phenyl and Si(CH3)3] and Me2C(115-C5H4-115- C9H6)ZrCh/MAO catalysts under different conditions. The resulting oligomers and polymers were characterized by GPC and NMR. Better conversions were obtained using catalysts with less bulky substituents and high MAO/catalyst ratios. Products ranged from dimeric oligomers to poly-u-olefins with molar masses between ca. 300 g.mol" and 6000 g.mol". Polydispersities, MwlMn, of poly-n-olefins synthesized at room temperatures were approximately 2, however, higher polydispersities were obtained at higher temperatures. Various end groups such as vinylidene, 1,2 disubstituted and 1,1,2 trisubstituted double bonds were observed and attributed to different propagation and termination reactions. The most important vinylidene end group corresponds to a specific 1,2 monomer insertion and termination by p-elimination.
AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van propeen/laer-a-olefien kopolimere en a-olefien homo-polimere wat berei is deur van metalloseen-katalisatore gebruik te maak. Die insluiting van 'n a-olefien ko-monomeer in die ruggraat van propileen het 'n verandering in eienskappe soos mikrostruktuur, smelting en die temperatuur van kristallisasie tot gevolg gehad. Die sintese van propeen/a-olefien (l-buteen, I-penteen, I-hekseen en 4-metiel-lpenteen) ko-polimere is uitgevoer met die katalisatorkombinasie Me2Si(2-Metielbenz[e] indeniel)2ZrClzIMAO. Daar is gepoog om die inkorporasie van die ko-monomeer tot <6% te beperk, om sodoende kristalliseerbare ko-polimere te verseker. Die komonomeerinhoud beïnvloed taktisiteit. Dit was veralopvallend in die propeen/l-buteen ko-polimere, en is toegeskryf aan die vorming van trosse (klusters) Die ko-polimere is gekarakteriseer deur van KMR, GPK, DSK en KRISTAF gebruik te maak. Die smelt-en kristallisasie-temperature (Tm (DSC), Tc (DSC) en Tc (CRYSTAF») van die propeen/Iaer-n-olefien ko-polimere het lineêr afgeneem met 'n toename in ko-monomeer inkorporasie en het sterk afgehang van van die tipe ko-monomeer. Die gedrag van laasgenoemde ko-polimere het verskil van dié van die propeenlhoër-a-olefien kopolimere (l-okteen, I-dekeen, I-tetradekeen, en l-oktadekeen). Die smelt- en kristallisasie-temperature van die propeen/4-metiel-l-penteen ko-polimere lê tussen dié van propeen/l-penteen en propeen/l-hekseen. Die poli-a-olefiene (l-penteen, I-hekseen,l-okteen en I-dekeen) is onder verskillende reaksiekondisies berei deur van die katalisatore (R-115-C9H6)zZrChIMAO [R=bensiel, feniel en Si(CH3)3] en Me2C(115-C514-115-C9H6)zrChIMAO.gebruik te maak. Die nuwe oligomere en polimere is met behulp van GPK en KMR gekarakteriseer. Katalisatore met kleiner substituente en hoër MAO/katalisator-verhoudings lewer beter omskakelings. Produkte het gevarieer vanaf dimeriese oligomere tot poli-a-olefiene met molêre massas tussen 300 en 6000 g.mol'. Die polidispersie van die poli-a-olefiene by kamertemperatuur gesintetiseer was ongeveer 2; hoër polidispersies is egter by hoër temperature verkry. Vinilideen, 1.2-disgesubstitueerde- en 1,1,2-trigesubsidueerde dubbelbindings is as eindgroepe waargeneem. Dit is toegeskryf aan verskillende voortplantings- en termineringsreaksies. Die belangrikste vinilideen-eindgroep stem ooreen met 'n spesifieke 1,2 monomeerinvoeging en terminering deur p-eliminasie.
39
Veighy, Clifford Robert. "Novel cyclopentadienyl transition metal complexes." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327366.
Full text
40
Beagan, Christina Majella. "The extrusion, performance and characterization of metallocene catalysed polyethylene based packaging films." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322767.
Full text
41
Conway, Stephen L. J. "Structure reactivity relationships in metallocene chemistry : the ansa-effect." Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:3a155469-19c6-4fbc-b77a-d24f8b27456e.
Full textAbstract:
This thesis is concerned with structure-reactivity relationships in metallocene chemistry. In particular new ansa-metallocenes of Groups 5-7 have been prepared. The structure and reactivity of these ansa-metallocenes is compared to the corresponding nonbridged metallocenes.
42
Heurtefeu, Bertrand. "Supports organiques à base de polyisoprène pour la catalyse de polymérisation de l’éthylène." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14123/document.
Full textAbstract:
Les travaux décrits dans ce manuscrit ont trait à l’élaboration de supports organiques fonctionnels à base de polyisoprène pour la catalyse de polymérisation de l’éthylène par les métallocène et post-métallocène. Une série de polyisoprènes ω-OH et de copolymères à blocs de type polyisoprène-b-poly(méthacrylate de méthyle) et polyisoprène-b-poly(oxyde d’éthylène) de masse molaire variable a été réalisée par polymérisation anionique vivante. L’auto-assemblage dans l’heptane de ces (co)polymères conduit à la formation d’agrégats micellaires stables qui permettent l’immobilisation des systèmes catalytiques via des interactions créées entre le bloc polaire du support et l’activateur aluminique, le plus souvent le méthylaluminoxane. La polymérisation de l’éthylène en présence de ces supports organiques conduit, sans diminution d’activité catalytique, à la formation de particules de polyéthylène de taille micrométrique. Selon la même méthodologie, des polyisoprènes portant à leur extrémité une fonction borate ont été synthétisés et avantageusement utilisés comme supports activateurs de métallocènes pré-alkylés. Dans ce cas, des particules de polyéthylène de taille millimétrique ont pu être obtenuesThe work described in this manuscript relates the development of organic functional supports based on polyisoprene for the catalysis of ethylene polymerization by metallocenes and post-metallocenes. Polyisoprenes ω-OH and block copolymers [polyisoprene-b-poly(methyl methacrylate) and polyisoprene-b-poly(ethylene oxide)] with different molecular weights were synthesized by living anionic polymerization. Self-assembly in heptane of (co)polymers leads to the formation of stable micellar aggregates allowing the immobilization of catalytic systems created thanks to interactions between the polar block of the support and the aluminic activator, the most often methylaluminoxane. The ethylene polymerization in the presence of organic support drives, without loss of catalytic activity, to the formation of polyethylene particles of micrometer size. Using the same methodology, polyisoprenes bearing at their ends a borate function have been synthesized and advantageously used as supports activators of pre-alkylated metallocenes. In this case, polyethylene particles with a millimeter size have been obtained
43
Osborne, James Daniel. "The synthesis of planar chiral metallocenes for application in asymmetric catalysis." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436806.
Full text
44
Amer, Ismael. "An investigation of the effect of chain length on stereo-regulation with C2 symmetric metallocene catalysts." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/3003.
Full textAbstract:
Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006.This study concerns the polymerization of propylene both in the presence and absence of molecular hydrogen. The percentage of hydrogen used as a terminating agent in the polymerization reactions was varied from 0.1 wt% to 15.0 wt% in order to compare a variety of polymers with different percentages of hydrogen incorporated. Two ansa metallocene catalysts were used: (A) rac-[ethylene bis(indenyl)] zirconium dichloride (rac-Et(Ind)2ZrCl2) and (B) dimethylsilyl-bis(2-methyl benzoindenyl) zirconium dichloride (rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2). Methylaluminoxane (MAO) was used as cocatalyst for both of the two catalysts. Characterization of the polymers included using nuclear magnetic resonance spectroscopy (NMR) for information concerning the microstructure of the polymers, high temperature gel permeation chromatography (HT-GPC) for molecular weight and molecular weight distributions and differential scanning calorimetry (DSC) to investigate the melting point and crystallization behaviour of the polymers. The polypropylenes prepared with the dimethylsilyl-bis(2-methyl benzoindenyl) zirconium dichloride catalyst system were compared to the polypropylenes synthesized with ethylene-bis(indenyl) zirconium dichloride. In particular, the effects of hydrogen on the microstructure, molecular weight, molecular weight distribution, melting point and crystallization behaviour were investigated.
45
Simerly, Thomas Max. "Immobilized Bis-Indenyl Ligands for Stable and Cost-Effective Metallocene Catalysts of Hydrogenation and Polymerization Reactions." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etd/1473.
Full textAbstract:
Reactions of catalytic hydrogenations and polymerizations are widely used in industry for manufacture of fine chemicals, pharmaceuticals, and plastics. Homogeneous catalysts for the processes that have low stability and their separation is difficult. Therefore, the development of new highly active and stable catalysts for hydrogenations and polymerizations is a necessity. The objective of this research was the development of a strategy for immobilization of heterogeneous metallocene catalysts. First, a methodology of immobilization of bis-indenyl ligands on the surface of mesoporous silica gel was designed. Four bis-indenyl ligands containing functionalized tethers of various lengths with terminal alkene groups were synthesized. All bis-indenyl ligands were immobilized on the surface of mesoporous functionalized silica gel by two methods: hydrosilylation and thiol-ene coupling of the double bond. After comparing the results, the second strategy was chosen as more efficient. The materials can be used further as intermediates for synthesis of supported metallocene catalysts.
46
Graef, Sven Markus. "Innovative spectroscopic and chromatographic techniques for the analysis of complex polyolefins prepared by metallocene catalysis." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52890.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2002.ENGLISH ABSTRACT: The study focused on the analysis of a variety o f synthesised tailored copolymers. During the investigation o f the samples new and innovative analytical techniques were developed to be able to identify the presence of certain predicted or expected copolymerisation products. Emphasis was placed on the versatility of CRYSTAF as a method for the analysis of semi-crystalline copolymers. Changes in the crystallisation temperature were used as an indicator, while the type o f method, solvent and sample weight served as variables in the system. The percentage comonomer content distribution for an unknown sample was determined from the standard curve plotted with the aid o f copolymers with known comonomer content. Ethylene/higher a-olefin and propylene/higher a-olefm copolymers were synthesised by means o f a metallocene precatalyst. In both cases, NMR spectroscopy, DSC, GPC, and CRYSTAF were used as analytical tools. In the ethylene series it was shown that the sample mixture was homogenous in the molar mass axis (GPC) but not in the chemical composition axis (CRYSTAF) regarding the comonomer content. For the propylene series, an increase in stereoerrors was observed by NMR and this was correlated with crystallisation on heating a DSC for the range o f copolymers. In the case where ethylene/methyl methacrylate block copolymers were synthesised using metallocene precatalyst, novel detection and separation methods were used and developed. This included the use o f CRYSTAF fitted with a carbonyl filter, high temperature gradient HPLC and high temperature liquid chromatography under critical conditions (LCCC). The last two techniques were the first where separation could be achieved with samples only dissolving at high temperature. All previous mentioned techniques, as well as the coupling of FTIR to GPC and high temperature gradient HPLC via LC-Transform revealed that the samples consisted o f varying ethylene and MMA block lengths.
AFRIKAANSE OPSOMMING: Die doelstelling van die navorsing was die analise van spesiaalvervaardigde kopolimere. Nuwe analitiese tegnieke is vir die bevestiging van sekere voorgestelde kopolimerisasie-produkte ontwikkel. Klem is gelê op die veelsydigheid van CRYSTAF as ’n metode vir die analise van gedeeltelik-kristallyne kopolimere. Veranderinge in die kristallisasie-temperature is as respons gebruik, terwyl die metode van sintese, die oplosmiddel en die hoeveelheid monster as veranderlikes in die sisteem beskou is. ‘n Standaardkurwe vir komonomeerinhoud is opgestel met behulp van kopolimere met ‘n bekende komonomeerinhoud. Hierdie kurwe is gebruik om die komonomeerinhoudsverspreiding van onbekende monsters te bepaal. Etileen/hoër a-olefien- en propileen/hoër a-olefien-kopolimere is met behulp van ‘n metalloseen pre-katalis gesintetiseer. In beide gevalle is KMR spektroskopie, DSC, GPC en CRYSTAF gebruik om die analises uit te uitvoer. Met verwysing na komonomeerinhoud is daar in die geval van die etileenreeks bevind dat die monstermengsel homogeen is met betrekking tot die molere massa, maar nie met betrekking tot die chemiese samestelling nie. Vir die propileenreeks is ’n verhoging in die stereofoute met behulp van KMR waargeneem. Dit is gekorrelleer met kristallisasie weens verhitting tydens DSC-bepalings vir die reeks kopolimere. In die geval van die sinteses van etileen/metielmetakrilaat-blokkopolimere met metalloseen as pre-katalis, moes nuwe waamemings- en skeidingstegnieke ontwikkel word. Dit het die gebruik van CRYSTAF met ’n karbonielfilter, hoetemperatuurgradient- HPLC en hoë-temperatuurvloeistofchromatografie onder kritiese toestande ingesluit. Laasgenoemde twee tegnieke het vir die eerste keer skeiding van monsters wat net by hoe temperature oplos, moontlik gemaak. Bogenoemde tegnieke, sowel as die koppeling van FTIR met GPC en hoë-temperatuur-gradient-HPLC via LC-transformasie het getoon dat die monsters etileen- en MMA-blokke met verskillende lengtes bevat het.
47
Sakamoto, Takahiro. "Relationships between Gas-Phase Ionization Energies and Solution-Phase Oxidation Potentials: Applications to the Electrocatalytic Production of Hydrogen from Weak Acids." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194534.
Full textAbstract:
The transfer of electrons to and from a molecule is one of the more fundamental and important chemical processes. One such important example is the reduction-oxidation (redox) cycles in catalysts and enzymes. In the hydrogenase enzymes, adding and removing electrons is one of the key processes for generating H₂ from water molecules. Finding a direct free energy relation between the vertical ionization energies (IE(V)) measured spectroscopically by gas-phase photoelectron spectroscopy and the oxidation potentials (E(1/2)) measured thermodynamically in solution by cyclic voltammetry (CV) for molecules is an important aspect for developing effective catalysts. In this study, a series of organometallic compounds such as metallocenes were used for investigating the free energy relationships and catalysts inspired by the active sites of [FeFe]-hydrogenases enzymes were evaluated for their ability to produce H₂ from electrocatalytic reduction of weak acids. The first part of the dissertation explores metallocenes of the form (η⁵-C₅H₅)₂M (M= Fe, Ru, Os, Co, Ni) as the model for developing the free energy relation between gas phase ionization energies (IE(V)) and solution oxidation potentials (E(1/2)). It was found that computing the electronic properties of Cp₂Fe, Cp₂Ru, and Cp₂Os using VWN-Stoll and OPBE density functional theory (DFT) functional was successful with root mean square deviation (RMSD) of 0.02 eV between the experimental and calculated ionization energies. However, calculated ionization energies of Cp₂Co and Cp₂Ni were less successful with RMSD of 0.3 eV between the experimental and calculated ionization energies. Introduction of the B3LYP or M06 hybrid DFT functionals yielded much improved results (0.1 eV) over the previous combinations of DFT functional for Cp2Co and Cp2Ni. The energy relation between the two experimental measurements was established and further computational studies revealed that the solvation energy was the largest energy contribution between IE(V) and E(1/2) in the five studied metallocenes. The RMSD of the calculated oxidation potentials, after adjusting for the error in gas-phase ionization energies, was 0.09 V. The second part of the dissertation explores a series of catalysts inspired by the active sites of [FeFe]-hydrogenase enzymes; μ-(2,3-pyrazinedithiolato)diironhexacarbonyl (PzDT-cat), Fe₂(μ-X₂C₅H₈O)(CO)₆ (where X = S, Se, Te), and Fe₂(μ-1,3-SC₃H₆X)(CO)₆ (where X = Se and Te) for their ability to produce H₂ from weak acids utilizing the computational techniques and knowledge gained from the metallocene study. Even though the overall electronic perturbation from μ-(1,2-benzenedithiolato)diironhexacarbonyl (BDT-cat) to μ-(2,3-pyridinedithiolato)diironhexacarbonyl (PyDT-cat) to PzDT-cat is found to be small, the reduction potential of PzDT-cat was found to be 0.15 V less negative than that of BDT-cat resulting in less energy required for initiating electrocatalytic H₂ production over the BDT-cat and PyDT-cat. Lower reorganization energy has been achieved by substitutions of larger chalcogens at the Fe₂S₂ core. However, the electrocatalytic production of H₂ from acetic acid in acetonitrile was found to be diminished upon going from analogous S to Se to Te species. This is ascribed to the increase in the Fe–Fe bond distance with a corresponding increase in the size of the chalcogen atoms from S to Se to Te, disfavoring the formation of a carbonyl-bridged structure in the anion which is thought to be critical to the mechanism of H₂ production.
48
Wood-Adams, Paula. "The effect of long chain branching on the rheological behavior of polyethylenes synthesized using constrained geometry and metallocene catalysts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0027/NQ50282.pdf.
Full text
49
Wilson, Duane C. "Synthesis, Structure, And Characterization Of Rare Earth(Iii) Transition Metal Cyanides; Lanthanide(Ii) And Metallocene Amidotrihydroborates." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1230880974.
Full text
50
Kim, Jung Dae. "Synthesis of polyolefins with controlled distributions of molecular weight and chemical composition by selective combination of supported metallocene/MAO catalysts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0018/NQ38248.pdf.
Full text