<p>Nanoparticles of iron, cobalt and tungsten oxide were synthesised by photolytic laser assisted chemical vapour deposition (LCVD). An excimer laser (operating at 193 nm) was used as an excitation source. The LCVD process, was monitored <i>in situ</i> by optical emission spectroscopy (OES). The synthesised particles were further analysed using transmission electron spectroscopy (TEM), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.</p><p>Iron and cobalt single crystalline nanoparticles were synthesized using ferrocene and cobaltocene precursors. The diameter of the particles could be tailored by the experimental parameters (e.g., partial pressure and laser power) and were in the range 1 - 50 nm in diameter. In both cases, the particles were covered by a carbon shell, typically 7 nm thick. A thin graphitic layer was observed at the interface metal-carbon. Amorphous carbon was deposited on top of the graphitic carbon. Particle temperature, reaching the boiling point of the respective metal, was observed by OES of the thermal emission during the laser-induced particle formation process (and subsequent heating). Both bcc and fcc Fe phases were formed, both hcp and fcc for the Co phases. Size dependent magnetic properties were observed using superconducting quantum interference device (SQUID) measurements, where super-paramagnetic magnetic domains dominated for <i>d</i> < 10 nm. The iron particles were further processed, whereby the amorphous shell was removed by refluxing in nitric acid. In a subsequent step, the graphitic surface was functionalized by attaching an octyl ester, rendering the particles hydrophobic.</p><p>Tungsten oxides were synthesized from combinations of WF₆/H₂/O₂ as precursors. No particles could be deposited if H₂ was removed from the gas-mixture. The as-deposited oxide nanoparticle film was amorphous. A monoclinic WO₃ particle film could be achieved by annealing the amorphous oxide. Above 400°C, the oxide particles increased in size from ca. 20 nm to 60 nm through coalescence. The gas-sensing properties of the tungsten oxide were tested by conductance measurements using H₂S as analyte. The sensitivity of the amorphous oxide nanoparticle film was found to be superior to that of a crystalline oxide nanoparticle film. </p>

Nanoparticles of iron, cobalt and tungsten oxide were synthesised by photolytic laser assisted chemical vapour deposition (LCVD). An excimer laser (operating at 193 nm) was used as an excitation source. The LCVD process, was monitored in situ by optical emission spectroscopy (OES). The synthesised particles were further analysed using transmission electron spectroscopy (TEM), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Iron and cobalt single crystalline nanoparticles were synthesized using ferrocene and cobaltocene precursors. The diameter of the particles could be tailored by the experimental parameters (e.g., partial pressure and laser power) and were in the range 1 - 50 nm in diameter. In both cases, the particles were covered by a carbon shell, typically 7 nm thick. A thin graphitic layer was observed at the interface metal-carbon. Amorphous carbon was deposited on top of the graphitic carbon. Particle temperature, reaching the boiling point of the respective metal, was observed by OES of the thermal emission during the laser-induced particle formation process (and subsequent heating). Both bcc and fcc Fe phases were formed, both hcp and fcc for the Co phases. Size dependent magnetic properties were observed using superconducting quantum interference device (SQUID) measurements, where super-paramagnetic magnetic domains dominated for d &lt; 10 nm. The iron particles were further processed, whereby the amorphous shell was removed by refluxing in nitric acid. In a subsequent step, the graphitic surface was functionalized by attaching an octyl ester, rendering the particles hydrophobic. Tungsten oxides were synthesized from combinations of WF6/H2/O2 as precursors. No particles could be deposited if H2 was removed from the gas-mixture. The as-deposited oxide nanoparticle film was amorphous. A monoclinic WO3 particle film could be achieved by annealing the amorphous oxide. Above 400°C, the oxide particles increased in size from ca. 20 nm to 60 nm through coalescence. The gas-sensing properties of the tungsten oxide were tested by conductance measurements using H2S as analyte. The sensitivity of the amorphous oxide nanoparticle film was found to be superior to that of a crystalline oxide nanoparticle film.

Alternative methods to control the molecular weight and short chain branching distribution of polyethylene were investigated. The ability to produce polyolefins with multimodal microstructural distributions using single catalyst/single reactor set-up is very attractive and could, in principle, be used to produce polyolefin resins with advanced molecular architecture. In this thesis, resins with controlled microstructures were produced, characterized and properties tested in order to develop a better understanding of polymerization structure-property relationships. Copolymerizations of ethylene and 1-hexene were carried out with an in-situ supported metallocene catalyst. Copolymers were produced with different alkylaluminum activators and the effect on molecular weight and short chain branching distributions was examined. It was found that different activator types produce polymer with unimodal and narrow molecular weight distributions but with very different short chain branching distributions. Each activator exhibits unique comonomer incorporation characteristics to produce bimodal short chain branching distributions with the use of a single activator. By using individual and mixed activator systems, it is possible to control the short chain branching distributions of the resulting copolymers while maintaining narrow molecular weight distributions. To further investigate the capabilities of this in-situ supported catalyst system, an experimental design was carried out to study the effect of polymerization conditions on the catalyst activity and microstructure of poly(ethylene-co-1-octene). The parameters investigated were: polymerization temperature, monomer pressure, chain transfer to hydrogen, comonomer/ethylene feed ratio and concentration of alkylaluminum. The effect of each parameter on the catalyst activity, comonomer incorporation and molecular weight distribution was investigated. The results obtained were not typical of a conventional single-site catalyst. The copolymerization system was sensitive to all of the parameters and many interactions were evident. The most prominent effect was the catalyst response to temperature. As the temperature was decreased, the short chain branching distributions of the copolymers became broad and bimodal. Overall, it was found that a wide range of microstructures could be produced, ranging from copolymers with low and high 1-octene content with unimodal to broad short chain branching distributions, and from low to high molecular weight with narrow to broad molecular weight distributions. To examine the effect of these broad short chain branching distributions on the polymer properties, a series of poly(ethylene-co-1-hexene) resins with very distinct, and in some cases bimodal crystalline distributions, were synthesized. The attractive feature of the resins in this study is that their molecular weight distributions are similar but each possesses a different short chain branching distribution, thus effectively minimizing the effect of molecular weight on the properties investigated. It was found that the tensile properties of a copolymer could be controlled by the ratio of the crystalline species present in the sample. In this study, a balance of stiffness and toughness was exhibited by a copolymer containing a large proportion of crystalline material and a small fraction of material of lower crystallinity. A series of poly(ethylene-co-1-octene) resins with tailored molecular weight and short chain branching distributions were synthesized with a heterogeneous metallocene catalyst in a two-stage polymerization process. Blends of high molecular weight copolymer and low molecular weight homopolymer and reverse blends of low molecular weight copolymer and high molecular weight homopolymer were produced. The physical properties of these resins were tested for their dynamic mechanical (tensile) and rheological properties. Increasing the copolymer content in the blend resulted in a decrease in stiffness. However, the energy dampening properties of these blends benefit from the presence of the copolymer. It was also confirmed that the melt flow properties of polymers mostly depend on their molecular weight distribution. Regardless of the comonomer content, the melt viscosities decreased with the addition of low molecular weight polymer.

Alternative methods to control the molecular weight and short chain branching distribution of polyethylene were investigated. The ability to produce polyolefins with multimodal microstructural distributions using single catalyst/single reactor set-up is very attractive and could, in principle, be used to produce polyolefin resins with advanced molecular architecture. In this thesis, resins with controlled microstructures were produced, characterized and properties tested in order to develop a better understanding of polymerization structure-property relationships. Copolymerizations of ethylene and 1-hexene were carried out with an in-situ supported metallocene catalyst. Copolymers were produced with different alkylaluminum activators and the effect on molecular weight and short chain branching distributions was examined. It was found that different activator types produce polymer with unimodal and narrow molecular weight distributions but with very different short chain branching distributions. Each activator exhibits unique comonomer incorporation characteristics to produce bimodal short chain branching distributions with the use of a single activator. By using individual and mixed activator systems, it is possible to control the short chain branching distributions of the resulting copolymers while maintaining narrow molecular weight distributions. To further investigate the capabilities of this in-situ supported catalyst system, an experimental design was carried out to study the effect of polymerization conditions on the catalyst activity and microstructure of poly(ethylene-co-1-octene). The parameters investigated were: polymerization temperature, monomer pressure, chain transfer to hydrogen, comonomer/ethylene feed ratio and concentration of alkylaluminum. The effect of each parameter on the catalyst activity, comonomer incorporation and molecular weight distribution was investigated. The results obtained were not typical of a conventional single-site catalyst. The copolymerization system was sensitive to all of the parameters and many interactions were evident. The most prominent effect was the catalyst response to temperature. As the temperature was decreased, the short chain branching distributions of the copolymers became broad and bimodal. Overall, it was found that a wide range of microstructures could be produced, ranging from copolymers with low and high 1-octene content with unimodal to broad short chain branching distributions, and from low to high molecular weight with narrow to broad molecular weight distributions. To examine the effect of these broad short chain branching distributions on the polymer properties, a series of poly(ethylene-co-1-hexene) resins with very distinct, and in some cases bimodal crystalline distributions, were synthesized. The attractive feature of the resins in this study is that their molecular weight distributions are similar but each possesses a different short chain branching distribution, thus effectively minimizing the effect of molecular weight on the properties investigated. It was found that the tensile properties of a copolymer could be controlled by the ratio of the crystalline species present in the sample. In this study, a balance of stiffness and toughness was exhibited by a copolymer containing a large proportion of crystalline material and a small fraction of material of lower crystallinity. A series of poly(ethylene-co-1-octene) resins with tailored molecular weight and short chain branching distributions were synthesized with a heterogeneous metallocene catalyst in a two-stage polymerization process. Blends of high molecular weight copolymer and low molecular weight homopolymer and reverse blends of low molecular weight copolymer and high molecular weight homopolymer were produced. The physical properties of these resins were tested for their dynamic mechanical (tensile) and rheological properties. Increasing the copolymer content in the blend resulted in a decrease in stiffness. However, the energy dampening properties of these blends benefit from the presence of the copolymer. It was also confirmed that the melt flow properties of polymers mostly depend on their molecular weight distribution. Regardless of the comonomer content, the melt viscosities decreased with the addition of low molecular weight polymer.

The present thesis deals with the synthesis, the reaction behavior, the solid-state structures, as well as the electrochemical properties of new heterobi- to heterotetrametallic transition metal complexes which are based on various ferrocenyl carboxylates and titanocenes of type [Ti](C≡CSiMe₃)₂ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti). <br/> Besides, the synthesis and the reaction behavior of bi- to heptametallic compounds, which are available from fc(CO₂H)(PPh₂) (fc = (η⁵-C₅H₄)₂Fe), is pointed out. By means of cyclovoltammetric measurements the electronic influence of additional transition metal complex fragments is investigated. <br/> A further main topic includes the synthesis of 1-amide-functionalized diphenylphosphinoferrocenes as well as the linking of diphenylphosphinoferrocenyl units to branched systems by means of amide bonds. The different coordination behavior of 1-amide-functionalized diphenylphosphinoferrocenes to Pd(II)-, Cd(II)-, and Hg(II)-salts is reflected and discussed in their solid-state structures. The suitability of such Pd(II)-compounds as catalytic active systems in Suzuki- and Heck-cross-coupling reactions is investigated. <br/> Moreover, the synthesis, structure, electronic, electrochemical, and magnetic properties of heterobimetallic Co(II)-, Ni(II)- and Cu(II)-complexes, based on 1,1‘-ferrocenyldicarboxylic units are presented. / Die vorliegende Arbeit befasst sich unter anderem mit der Synthese, dem Reaktionsverhalten, den Festkörperstrukturen sowie den elektrochemischen Eigenschaften neuartiger heterobi- bis heterotetrametallischer Übergangsmetallkomplexe, welche auf verschiedenen Ferrocenylcarboxylaten und Titanocenen des Typs [Ti](C≡CSiMe₃)₂ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) basieren. Weiterhin wird die Darstellung und das Reaktionsverhalten bi- bis heptametallischer Verbindungen aufgezeigt, welche ausgehend vom 1,1’-funktionalisierten Ferrocen fc(CO₂H)(PPh₂) (fc = (η⁵-C₅H₄)₂Fe) zugänglich sind. Durch cyclovoltammetrische Untersuchungen wird der elektronische Einfluß weiterer Übergangsmetallkomplexfragmente im System untersucht. Ein weiterer Schwerpunkt der Arbeit umfasst die Darstellung von 1-amidfunktionalisierten Diphenylphosphinoferrocenen sowie die Anknüpfung von Diphenylphosphinoferrocenyl-Einheiten über Amidbindungen an verzweigte Systeme. Das unterschiedliche Koordinationsverhalten von 1-amidfunktionalisierten Diphenylphosphinoferrocenen gegenüber Pd(II)-, Cd(II)- und Hg(II)-Salzen ist in ihren Festkörperstrukturen erkennbar und wird diskutiert. Die Eignung derartiger Pd(II)-Verbindungen als katalytisch aktive Systeme in Suzuki- und Heck-Kreuzkupplungen wird untersucht. Ferner werden Darstellung, Struktur, elektronische, elektrochemische und magnetische Eigenschaften von heterobimetallischen Co(II)-, Ni(II)- und Cu(II)-Komplexen basierend auf 1,1’-Ferrocenyldicarboxylat-Einheiten aufgezeigt.

1 Ziel und Gegenstand der Untersuchungen Gegenstand der vorliegenden Arbeit war die Synthese und Charakterisierung von polaren Olefin-basierten Makromonomeren mit Hilfe von Metallocen-Katalysatoren. Polyolefine stellen eine Gruppe von Polymeren dar, die durch Additive oder chemische Veränderungen modifiziert, eine große Vielfalt von Einsatzmöglichkeiten auf der Basis einfach aufgebauter Monomere bieten. Sie stellen deshalb heutzutage die wichtigste Kunststoffgruppe dar. Ein Nachteil ist jedoch die unpolare Struktur dieser Polymere. Ziel dieser Arbeit war die Homopolymerisation polarer Olefine, um ein funktionalisiertes Polyolefin zu erzeugen, dass zudem auch als Makromonomer einsetzbar ist. Als Katalysatoren wurden im Wesentlichen die klassischen Metallocene auf Zr-Basis eingesetzt, aktiviert mit MAO. Die Makromonomere wurden im Anschluss an die Synthese umfassend charakterisiert. 2 Ergebnisse Zur Synthese wurde das bekannte 10-Undecen-1-ol (Undecenol) eingesetzt. Für eine erfolgreiche Homopolymerisation dieses Monomers ist eine effektive Abschirmung des Katalysators gegenüber der polaren Gruppe zur Minimierung der Deaktivierung des Katalysators zu gewährleisten. Für die Einführung von Schutzgruppen fand Triisobutylaluminium (TIBA) Verwendung. Auf diese Weise konnte erstmalig erfolgreich die Synthese von Polyundecenol mit Metallocen-Katalysatoren durchgeführt werden. Es zeigte sich, dass Undecenol als polares und zugleich sterisch anspruchsvolles Monomer mit der überwiegenden Anzahl der eingesetzten Metallocene schwierig zu polymerisieren ist, was im Vergleich zur Polymerisation von kurzkettigen 1 Olefinen, wie zum Beispiel Propen, anhand von geringen Molmassen (< 2000 g/mol) aber auch geringen Ausbeuten zum Ausdruck kommt. Die erzielten Molmassen der Polyundecenole sind jedoch für die Verwendung als Makromonomer vorteilhaft. Die höchsten Polymerausbeuten ermöglichte der Einsatz von ansa-Metallocenen. Mit dem Katalysator Et[Ind]2ZrCl2 konnten hierbei relative Ausbeuten im Bereich von 50 % bis 60 % bei gleichzeitig geeigneten Molmassen von < 10^4 g/mol erzielt werden. Bei der Verwendung von unverbrückten Metallocenen (bis-Cyclopentadienylkomplexe) sind die Ausbeuten und Molmassen im Vergleich zu den ansa-Metallocenen deutlich reduziert. Die synthetisierten Polyundecenole wurden hinsichtlich ihres Schmelz- und Kristallisationsverhaltens sowie der kristallinen Struktur untersucht und der Zusammenhang mit der Taktizität und der Molmasse der Polymere hergestellt. Die Ergebnisse der DSC und WAXS Untersuchungen lassen darauf schließen, dass für ataktische und isotaktische Polyundecenole eine Seitenkettenkristallisation als primäre Form der Kristallisation vorliegt. Aufgrund des hohen Gehalts von Hydroxylgruppen, die durch Wasserstoffbrückenbindungen wechselwirken, weist Polyundecenol hohe Schmelztemperaturen auf, im Vergleich mit dem unpolaren Poly(1-Undecen). So besitzt isotaktisches und auch ataktisches Polyundecenol bei vergleichbaren Molmassen eine um rund 80 K höhere Schmelztemperatur als Poly(1-Undecen). Die Wechselwirkung der Hydroxylgruppen wurde mittels FTIR-Spektroskopie nachgewiesen und liegt auch im geschmolzenen Zustand der Polymere vor. Anhand der Ergebnisse von WAXS-Untersuchungen konnte gezeigt werden, dass Polyundecenol in smektischen Schichten kristallisiert. Der Abstand zwischen den Hauptketten entspricht etwa zwei vollständig gestreckten Seitenketten des Polymers, welche orthogonal zur Hauptkette angeordnet sind. Diese Schicht-Anordnung wurde unabhängig von Molmasse und Taktizität der Polymere nachgewiesen und lässt die Schlussfolgerung zu, dass die Kristallisation isotaktischer Rückgrat-Ketten gegenüber der Seitenketten-Kristallisation unterdrückt ist. Es wurde jedoch beobachtet, dass die Taktizität einen Einfluss auf die Kristallisation hat. Polyundecenole mit isotaktischer Hauptkette weisen bei entsprechend langsamer Kristallisation eine Anordnung der Seitenketten in einer monoklinen Packung auf, was als Hinweis auf eine Kristallisation der Hauptkette interpretiert wird, auch wenn diese im Rahmen der Arbeit nicht eindeutig nachgewiesen werden konnte. Bei Polyundecenolen mit ataktischer Hauptkette ordnen sich die Seitenketten hingegen in einer hexagonalen Packung an, da die Hauptkette nicht in der Lage ist zu kristallisieren. Von besonderer Bedeutung für die Synthese der Polyundecenole waren einerseits die erzielbaren Polymerausbeuten, andererseits aber auch die Einführung geeigneter Endgruppen, welche ausschlaggebend sind für eine Nutzung als Makromonomer. Die Untersuchungen zum Polymerisationsverhalten verschiedener Metallocen-Katalysatoren zeigten, dass im Falle von ansa-Metallocenen sowie einem "CGC"-Komplex Polymere erhalten werden, die vor allem Endgruppen mit internen Doppelbindungen, doppelt- und dreifachsubstituiert, aufweisen. Solche Endgruppen sind jedoch für einen späteren Einsatz der Polymere als Makromonomer ungeeignet. Der Einsatz von unverbrückten Metallocen-Katalysatoren auf Basis der Biscyclopentadienyl-Struktur ermöglicht hingegen die Synthese von Polyundecenol mit einem hohen Anteil endständiger Vinyliden-Endgruppen zu synthetisieren. Die so erreichten Vinyliden-Endgruppenanteile bewegten sich nahezu unabhängig vom Katalysator im Bereich von etwa 85 % bis 90 %. Ein wesentliches Ergebnis der Arbeit stellt die Synthese von Polyundecenol mit Allyl-Endgruppen dar. Dieses wurde durch gezielte Kettenabbruchreaktionen mit Hilfe von Vinylchlorid erreicht. Bei Einsatz des Katalysator MBI konnten Anteile der favorisierten Allyl-Endgruppe von rund 90 % erreicht werden. Somit wurden auf diesem Wege erstmalig erfolgreich Polyundecenol-Makromonomere synthetisiert. Ein Einsatz dieser Polymere in der Copolymerisation mit Propen wurde aber durch geringe Ausbeuten verhindert. Jedoch konnte gezeigt werden, dass der Einsatz von Vinylchlorid die Synthese von Polyundecenol-Makromonomeren ermöglicht.

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. <strong>Chapter 1</strong> 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. <strong>Chapter 2</strong> 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)<sub<2</sub>}M(η⁵-C₅H₅)Cl] (M = Zr, Hf) is also described, along with their X-ray crystal structures. The variable temperature solid state ¹³C CP/MAS NMR spectra of [{Me₂C(η⁵-C₅H₄)<sub<2</sub>}M(η⁵-C₅H₅)Cl] (M = Zr, Hf) show slow rotation of the C₅H₅ ring on the NMR timescale. <strong>Chapter 3</strong> describes the synthesis and characterisation of some novel homo- and hetero-binuclear metallocene compounds of zirconium and hafnium in which the metals are bridged by an unsymmetrical ansa ligand. The novel, chiral homobinuclear compounds [(η⁵-C₅H₅)MCl₂{(η⁵-C₅H₄)CMe₂(η⁵-C₉H₆)}MCl₂(η⁵-C₅H₅)] (M = Zr, Hf) are described. The ansa-bridged mononuclear compounds [{Me₂C(η⁵-C₅H₄)(η²-C₉H₇)M(η⁵-C₅H₅)Cl] (M = Zr, Hf) are used as reagents for the selective synthesis of the heterobinuclear analogues [(η⁵-C₅H₅)MCl₂{(η⁵-C₅H₄)CMe₂(η⁵-C₉H₆)}M*Cl₂(η⁵-C₅H₅)] (M = Zr, M* = Hf ; M = Hf, M* = Zr) and the unsymmetrical homobinuclear compound [(η⁵-C₅H₅)ZrCl₂{(η⁵-C₅H₄)CMe₂(��⁵-C₉H₆)}ZrCl₂(η⁵-C₅Me₅)]. The methylated derivatives [(η⁵-C₅H₅)M(CH₃)₂{(η⁵-C₅H₄)CMe₂(η⁵-C₅H₆)}M*(CH₃)₂(η⁵-C₅H₅)] (M = Zr, M* = Zr, Hf; M = Hf, M* = Zr, Hf) are also described. The structurally related mononuclear compounds [(η⁵-C₅H₅)MCl₂{(η⁵-C₅H₄)CMe₂(C₉H₇)}] (M = Zr, Hf) and [(η⁵-C₅H₅)Zr(CH₃)₂{(η⁵-C₅H₄)CMe₂(C₉H₇)}] have also been prepared. <strong>Chapter 4</strong> presents some olefin polymerization studies using the new compounds described in Chapter 3 as catalysts, along with either methylaluminoxane or the recently developed co-catalysts [Ph₃C]⁺[B(C₆F₅)₄]^- and B(C₆F₅)₃. <strong>Chapter 5</strong> provides the experimental details for the reactions described in this thesis and the characterising data for all new compounds are given in <strong>Chapter 6</strong> Crystallographic data for the for the X-ray structure determinations in Chapter 2 are given in the <strong>Appendices</strong>.

Techn. Universiẗat, Diss., 2001--Darmstadt.

Techn. Universiẗat, Diss., 2001--Chemnitz.

Universiẗat, Diss., 2004--Düsseldorf.