In this thesis chemical reactions under hydrothermal conditions were explored, whereby emphasis was put on green chemistry. Water at high temperature and pressure acts as a benign solvent. Motivation to work under hydrothermal conditions was well-founded in the tunability of physicochemical properties with temperature, e.g. of dielectric constant, density or ion product, which often resulted in surprising reactivity. Another cornerstone was the implementation of the principles of green chemistry. Besides the use of water as solvent, this included the employment of a sustainable feedstock and the sensible use of resources by minimizing waste and harmful intermediates and additives. To evaluate the feasibility of hydrothermal conditions for chemical synthesis, exemplary reactions were performed. These were carried out in a continuous flow reactor, allowing for precise control of reaction conditions and kinetics measurements. In most experiments a temperature of 200 °C in combination with a pressure of 100 bar was chosen. In some cases the temperature was even raised to 300 °C. Water in this subcritical range can also be found in nature at hydrothermal vents on the ocean floor. On the primitive earth, environments with such conditions were however present in larger numbers. Therefore we tested whether biologically important carbohydrates could be formed at high temperature from the simple, probably prebiotic precursor formaldehyde. Indeed, this formose reaction could be carried out successfully, although the yield was lower compared to the counterpart reaction under ambient conditions. However, striking differences regarding selectivity and necessary catalysts were observed. At moderate temperatures bases and catalytically active cations like Ca2+ are necessary and the main products are hexoses and pentoses, which accumulate due to their higher stability. In contrast, in high-temperature water no catalyst was necessary but a slightly alkaline solution was sufficient. Hexoses were only formed in negligible amounts, whereas pentoses and the shorter carbohydrates accounted for the major fraction. Amongst the pentoses there was some preference for the formation of ribose. Even deoxy sugars could be detected in traces. The observation that catalysts can be avoided was successfully transferred to another reaction. In a green chemistry approach platform chemicals must be produced from sustainable resources. Carbohydrates can for instance be employed as a basis. They can be transformed to levulinic acid and formic acid, which can both react via a transfer hydrogenation to the green solvent and biofuel gamma-valerolactone. This second reaction usually requires catalysis by Ru or Pd, which are neither sustainable nor low-priced. Under hydrothermal conditions these heavy metals could be avoided and replaced by cheap salts, taking advantage of the temperature dependence of the acid dissociation constant. Simple sulfate was recognized as a temperature switchable base. With this additive high yield could be achieved by simultaneous prevention of waste. In contrast to conventional bases, which create salt upon neutralization, a temperature switchable base becomes neutral again when cooled down and thus can be reused. This adds another sustainable feature to the high atom economy of the presented hydrothermal synthesis. In a last study complex decomposition pathways of biomass were investigated. Gas chromatography in conjunction with mass spectroscopy has proven to be a powerful tool for the identification of unknowns. It was observed that several acids were formed when carbohydrates were treated with bases at high temperature. This procedure was also applied to digest wood. Afterwards it was possible to fermentate the solution and a good yield of methane was obtained. This has to be regarded in the light of the fact that wood practically cannot be used as a feedstock in a biogas factory. Thus the hydrothermal pretreatment is an efficient means to employ such materials as well. Also the reaction network of the hydrothermal decomposition of glycine was investigated using isotope-labeled compounds as comparison for the unambiguous identification of unknowns. This refined analysis allowed the identification of several new molecules and pathways, not yet described in literature. In summary several advantages could be taken from synthesis in high-temperature water. Many catalysts, absolutely necessary under ambient conditions, could either be completely avoided or replaced by cheap, sustainable alternatives. In this respect water is not only a green solvent, but helps to prevent waste and preserves resources. / In dieser Arbeit wurden chemische Reaktionen unter Hydrothermalbedingungen untersucht. Darunter versteht man Wasser als Reaktionsmedium, welches eine Temperatur über 100 °C aufweist. Der flüssige Zustand wird dabei durch erhöhten Druck aufrecht erhalten. Typischerweise wurden die Reaktionen bei 200 °C und einem Druck von 100 bar durchgeführt, also dem 100-fachen des Normaldrucks. Dieses System kann man auch mit einem Dampfdrucktopf vergleichen, wobei durch die erhöhten Temperaturen chemische Reaktionen sehr schnell ablaufen und überraschende Reaktivität auftritt. Die Motivation, Wasser als Lösemittel zu benutzen, ist auch in seiner Umweltfreundlichkeit gegenüber klassischen organischen Lösemitteln begründet. Da solche Hydrothermalbedingungen auf der frühen Erde häufiger anzutreffen waren, wurde untersucht, ob wichtige Biomoleküle bei solch hoher Temperatur gebildet werden können. In der Tat konnten Zucker aus der sehr einfachen Verbindung Formaldehyd synthetisiert werden. Hierzu war lediglich eine leicht basische Lösung nötig und keine der bei moderaten Temperaturen essentiellen Katalysatoren. Zucker stellen zudem den größten Teil der pflanzlichen Biomasse dar und können daher als Grundlage für eine nachhaltige Chemie dienen. Sie können relativ einfach zu Lävulin- und Ameisensäure umgesetzt werden. Aus diesen wiederum kann die wichtige Basischemikalie gamma-Valerolacton hergestellt werden. Der Schlüsselschritt, die Reduktion von Lävulinsäure, erforderte bisher die Zuhilfenahme seltener Edelmetalle wie Ruthenium. Es konnte nun gezeigt werden, dass unter Hydrothermalbedingungen diese Rolle von einfachen Salzen, z. B. Natriumsulfat, übernommen werden kann. Hierbei macht man sich zunutze, dass sie nur bei hoher Temperatur basisch wirken, nicht aber wenn die Lösung wieder abgekühlt ist. Neben Kohlenhydraten besteht Biomasse auch aus Aminosäuren, von denen Glycin die einfachste darstellt. Unter Abspaltung von CO2 können aus ihnen synthetisch wichtige Amine hergestellt werden. Diese Reaktion findet unter Hydrothermalbedingungen statt, daneben treten jedoch noch andere Produkte auf. Unbekannte Verbindungen wurden mittels Massenspektroskopie identifiziert, wobei die Masse des Moleküls und bestimmter Molekülfragmente bestimmt wurde. Dies erlaubte es, bisher noch unbekannte Reaktionswege aufzuklären. Zusammenfassend lässt sich sagen, dass Wasser unter Hydrothermalbedingungen eine interessante Alternative zu organischen Lösemitteln darstellt. Desweiteren können bestimmte Katalysatoren, die bei moderaten Temperaturen nötig sind, entweder vollständig eingespart oder ersetzt werden. In dieser Hinsicht ist Wasser nicht nur ein umweltfreundliches Lösemittel, sondern trägt dazu bei, Abfall zu vermeiden und Ressourcen zu schonen.

Orientador: Prof. Dr. Wagner Alves Carvalho / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2015. / O aumento da demanda energética e depreciação das reservas de combustíveis fósseis implicam na adoção de metodologias que estimulem a utilização de fontes alternativas na produção de combustíveis. A biomassa possui considerável importância neste cenário, sendo uma promissora fonte de energia renovável quando convertida a combustíveis e produtos químicos de importância industrial. Reações de desidratação e hidrogenação ocorrem em meio ácido, podendo ser catalisadas por sólidos ácidos. O objetivo deste trabalho foi avaliar a atividade de catalisadores mono- e bimetálicos, contendo Sn e Ru suportados em carvão, assim como o impacto do aumento da acidez do meio utilizando sólidos sulfonados como co-catalisadores. As condições foram otimizadas para a reação com um catalisador comercial 5 % de Ru em carvão. Neste trabalho foram testados nióbia (CBMM ¿ HY-340), argila pilarizada (Fluka) e carvão (Darco) sulfonado na conversão do ácido levulínico. Com o intuíto de otimizar a reação de hidrogenação avaliou-se o uso de carvão variando-se a relação metálica Sn/Ru. Os sólidos foram tratados com ácido sulfúrico fumegante concentrado, os carvões contendo metal sofreram impregnação sucessiva e impregnação simultânea. A presença de grupos sulfônicos e o aumento da acidez dos sólidos demonstram a adequação do processo de sulfonação. O melhor catalisador para reação de hidrogenação do ácido levulínico foi o carvão Darco contendo Sn-Ru 1:0,5, associado ao co-catalisador carvão sulfonado, apresentando conversão de 75% após duas horas de reação e 98% de seletividade para GVL, à 100 °C e pressão de 30 bar de hidrogênio. / Increasing energy demand and depreciation of the fossil fuels reserves implicate in the adoption of methodologies that stimulate the use of alternative sources in the production of fuels. Biomass has considerable importance in this scenario, being a promising source of renewable energy when converted to fuels and chemical products of industrial importance. Dehydration and hydrogenation reactions take place in acid medium, and may be catalyzed by acid solids. The objective of this work was to evaluate the activity of monometallic and bimetallic catalysts, containing Sn and Ru supported on carbon, as well as the impact of the increase of the acidity in the reaction system using sulfonated solids as co-catalysts. Reaction conditions were optimized with a commercial catalyst, 5% of Ru supported on carbon. In this work niobia (CBMM. HY -340), pillared clay (Fluka) and sulfonated carbon (Darco) were tested in the conversion of the levulinic acid. With the aim of optimizing the hydrogenation reaction the use of carbon was evaluated by varying the Sn/Ru metallic relationship. The solids were treated with concentrated fuming sulfuric acid, while the carbon containing both Sn and Ru was submitted to successive and simultaneous impregnation processes. The presence of sulfonic acid groups and the increase of the acidity of the solids demonstrate the viability of the sulfonation process. The best catalyst for reaction of levulinic acid hydrogenation was Darco carbon containing Sn-Ru 1:0,5, associated to the sulfonated carbon as co-catalyst, presenting conversion of 75% after 2 h reaction time and 98% of selectivity for GVL, under 100 °C and hydrogen pressure of 30 bar.

A systematic silylation approach using mono-, di-, and trichlorosilanes with different alkyl chain lengths was employed to enhance the hydrothermal stability of zeolite Y. DRIFT spectra of the silylated zeolites indicate that the attachment of the silanes takes place at surface silanol groups. Regarding hydrothermal stability under aqueous-phase processing (APP) conditions, i.e., pH ≈ 2, 473 K and autogenous pressure, the selective silylation of the zeolite surface usingmonochlorosilanes has no considerable influence. By using trichlorosilanes, the hydrothermal stability of zeolite Y can be improved significantly as proven by a stability test in an aqueous solution of 0.2M levulinic acid (LA) and 0.6M formic acid (FA) at 473 K. However, the silylationwith trichlorosilanes results in a significant loss of total specific pore volume and total specific surface area, e.g., 0.35 cm3 g−1 and 507m2 g−1 for the silylated zeolite Y functionalized with n-octadecyltrichlorosilane compared to 0.51 cm3 g−1 and 788 m2 g−1 for the parent zeolite Y. The hydrogenation of LA to g-valerolactone (GVL) was conducted over 3 wt.-% Pt on zeolite Y (3PtY) silylated with either n-octadecyltrichlorosilane or methyltrichlorosilane using different reducing agents, e.g., FA or H2. While in the stability test an enhanced hydrothermal stability was found for zeolite Y silylated with n-octadecyltrichlorosilane, its stability in the hydrogenation of LA was far less pronounced. Only by applying an excess amount of methyltrichlorosilane, i.e., 10 mmol per 1 g of zeolite Y, presumably resulting in a high degree of polymerization among the silanes, a recognizable improvement of the stability of the 3 PtY catalyst could be achieved. Nonetheless, the pore blockage found for zeolite Y silylated with an excess amount of methyltrichlorosilane was reflected in a drastically lower GVL yield at 493 K using FA as reducing agent, i.e., 12 vs. 34% for 3PtY after 24 h.

Des ligands diketimines porteurs de substituants N-benzyl, N-9-anthrylmethyl et N-mesitylmethyl (nacnacBnH, nacnacAnH, and nacnacMesH) ont été synthétisés par condensation d’une amine et d’acétyl acétone ou son monoacétal d’éthylène glycol. La chlorination de la position 3 a été effectuée à l’aide de N-chlorosuccinimide conduisant à la formation des ligands ClnacnacBnH et ClnacnacAnH. Cette même position 3 a également été substituée par un groupement succinimide par lithiation du nacnacBnH, suivi de la réaction avec le N-chlorosuccinimide (3-succinimido-nacnacBnH). Les ligands N-aryl nacnacippH et nacnacNaphH (ipp = 2-isopropylphenyl, Naph = 1-naphthyl) ont été préparés selon les procédures reportées dans la littérature. La réaction de ces ligands avec Zn(TMSA)2 (TMSA = N(SiMe3)2) conduit à la formation des complexes nacnacAnZn(TMSA) et ClnacnacBnZn(TMSA). La protonation avec l’isopropanol permet l’obtention des complexes nacnacAnZnOiPr et ClnacnacBnZnOiPr. La réaction avec Mg(TMSA)2 permet quant à elle la formation des complexes nacnacAnMg(TMSA), nacnacMesMg(TMSA), ClnacnacBnMg(TMSA) et ClnacnacAnMg(TMSA). La protonation subséquente à l’aide du tert-butanol permet l’obtention du nacnacMesMgOtBu et du ClnacnacBnMgOtBu, alors que l’on observe uniquement une décomposition avec les ligands possédant des substituants N-anthrylmethyl. La réaction de ces diketimines avec Cu(OiPr)2 conduit aux dimères hétéroleptiques [nacnacBnCu(μ-OiPr)]2 et [3-Cl-nacnacBnCu(μ-OiPr)]2 lors de l’usage des ligands stériquement peu encombrés. Lors de l’utilisation de ligands plus encombrés, la stabilisation du complexe hétéroleptique par dimérisation n’est plus possible, conduisant, par un échange de ligand, à la formation des complexes homoleptiques Cu(nacnacipp)2 et Cu(nacnacNaph)2. Les complexes homoleptiques Cu(nacnacBn)2 et Cu(3-succinimido-nacnacBn)2 ont été obtenus à partir des ligands N-benzyl. Les ligands encore plus encombrés tels que nacnacAnH, nacnacMesH ou ceux comportant des substituants N-methylbenzyl ne présentent alors plus de réactivité avec le Cu(OiPr)2. La plupart des complexes ont été caractérisés par Diffraction des Rayons X. Les complexes homoleptiques ainsi que ceux de TMSA sont monomériques, alors que ceux formés à partir d’alkoxides se présentent sous forme de dimères à l’état solide. Tous les complexes d’alkoxides ainsi que les nacnacAnMg(TMSA)/BnOH et ClnacnacAnMg(TMSA)/BnOH présentent une réactivité modérée à haute en matière de polymérisation du rac-lactide (90% de conversion en 30 secondes à 3 heures). Le nacnacAnZnOiPr permet la synthèse d’un polymère hautement hétérotactique (Pr = 0.90) quand le ClnacnacBnMgOtBu/BnOH génère un polymère isotactique à -30°C (Pr = 0.43). Tous les autres catalyseurs produisent des polymères atactiques avec une légère tendance hétérotactique (Pr = 0.48 – 0.55). Les complexes hétéroleptiques [nacnacBnCu(μ-OiPr)]2 et [3-Cl-nacnacBnCu(μ-OiPr)]2 se révèlent être de très bons catalyseurs pour la polymérisation du rac-lactide présentant une conversion complète du monomère à température ambiante, en solution, en 0,5 à 5 minutes. Le [nacnacBnCu(μ-OiPr)]2 est actif en présence ou absence d’isopropanol, agissant comme agent de transfert de chaine à haute activité (k2 = 32 M–1•s–1) dans le dichlorométhane. Dans l’acétonitrile, le THF, le dichloromethane et le toluène, [nacnacBnCu(μ-OiPr)]2 conduit à une étroite polydispersité, possédant respectivement des kobs = 2.4(1), 5.3(5), 3.6-4.4 and 10(1) min–1. Aucune réaction parasite, telle qu’une trans-esterification, une épimerisation ou une décomposition du catalyseur, n’a été observée. Les complexes homoleptiques en présence d’alcool libre semblent présenter un équilibre avec une petite quantité de leurs équivalents hétéroleptiques, permettant une polymérisation complète, en moins de 60 min, à température ambiante. Tous les catalyseurs de cuivre présentent un haut contrôle de la polymérisation avec une polydispersité égale ou inférieure à 1.1. Les polymères obtenus sont essentiellement atactiques, avec une légère tendance à l’hétérotacticité à température ambiante et -17°C. Le [nacnacBnCu(μ-OiPr)]2 polymérise également la -butyrolactone (BL), l’-caprolactone (CL) et la -valerolactone (VL) avec des constantes respectivement égales à kobs = 3.0(1)•10–2, 1.2–2.7•10–2, et 0.11(1) min–1. Les homopolymères présentent une étroite polydispersité d’approximativement 1.1. Les polymérisations par addition séquentielle ont mis en évidence une trans-estérification (non observée dans les homopolymérisations) si BL ou CL sont introduits après un bloc lactide. / Diketimine ligands bearing N-benzyl, N-9-anthrylmethyl and N-mesitylmethyl substituents (nacnacBnH, nacnacAnH, and nacnacMesH) were prepared from condensation of amine with either acetyl acetone or its ethylene glycol monoketal. Chlorination of the 3-position was achieved using N-chlorosuccinimide, yielding ClnacnacBnH and ClnacnacAnH. The 3-position was also substituted by succinimido by lithiation of nacnacBnH followed by reaction with N-chlorosuccinimide (3-succinimido-nacnacBnH). N-aryl ligands nacnacippH and nacnacNaphH (ipp = 2-isopropylphenyl, Naph = 1-naphthyl) were prepared from literature. The ligands were reacted with Zn(TMSA)2 (TMSA = N(SiMe3)2) to yield nacnacAnZn(TMSA) and ClnacnacBnZn(TMSA). Protonation with isopropanol gave nacnacAnZnOiPr and ClnacnacBnZnOiPr. Reaction of the diketimines with Mg(TMSA)2 afforded nacnacAnMg(TMSA), nacnacMesMg(TMSA), ClnacnacBnMg(TMSA) and ClnacnacAnMg(TMSA). Subsequent protonation with tert-butanol produced nacnacMesMgOtBu and ClnacnacBnMgOtBu, but only decomposition was observed with N-anthrylmethyl substituents. Reaction of the diketimines with Cu(OiPr)2 yielded the heteroleptic [nacnacBnCu(μ-OiPr)]2 and [3-Cl-nacnacBnCu(μ-OiPr)]2 when using sterically undemanding ligands. When sterically more demanding diketimines were used, stabilization of the heteroleptic complex by dimerization was not possible, resulting in the formation of the homoleptic complexes Cu(nacnacipp)2 and Cu(nacnacNaph)2 by ligand exchange. Homoleptic complexes were also prepared with N-benzyl ligands, i. e. Cu(nacnacBn)2 and Cu(3-succinimido-nacnacBn)2. Even bulkier ligands such as nacnacAnH, nacnacMesH or N-methylbenzyl substituents failed to react with Cu(OiPr)2. Most complexes were characterized by single crystal X-ray diffraction. TMSA complexes and homoleptic complexes were monomeric, alkoxide complexes were dimeric in the solid state. All alkoxide complexes, as well as nacnacAnMg(TMSA)/BnOH and ClnacnacAnMg(TMSA)/BnOH were moderately to highly active in rac-lactide polymerization (90% conversion in 30 sec to 3 h). nacnacAnZnOiPr produced highly heterotactic polymer (Pr = 0.90), ClnacnacBnMgOtBu/BnOH produced slightly isotactic polymer at –30 °C (Pr = 0.43), all other catalysts produced atactic polymers with a slight heterotactic bias (Pr = 0.48 – 0.55). Heteroleptic complexes [nacnacBnCu(μ-OiPr)]2 and [3-Cl-nacnacBnCu(μ-OiPr)]2 are very highly active rac-lactide polymerization catalysts, with complete monomer conversion at ambient temperature in solution in 0.5 – 5 min. [nacnacBnCu(μ-OiPr)]2 specifically polymerized in the presence or absence of isopropanol as a chain-transfer reagent with very high activity (k2 = 32 M–1•s–1), in methylene chloride. While in acetonitrile, THF, dichloromethane and toluene has a kobs = 2.4(1), 5.3(5), 3.6-4.4 and 10(1) min–1, respectively. [nacnacBnCu(μ-OiPr)]2 yields narrow polydispersities and no evidence of side reactions such as transesterification, epimerization or catalyst decomposition. The homoleptic complexes in the presence of free alcohol, seem to be in equilibrium with small amounts of the respective heteroleptic complex, which are sufficient to complete polymerization in less than 60 min at room temperature. All Cu catalysts show high control of polymerization with polydispersities of 1.1 and below. The obtained polymers were essentially atactic, with a slight heterotactic bias at ambient temperature and at –17 °C. [nacnacBnCu(μ-OiPr)]2 polymerizes -butyrolactone (BL), -caprolactone (CL) and -valerolactone (VL) with rate constants of kobs = 3.0(1)•10–2, 1.2–2.7•10–2, and 0.11(1) min–1, respectively. Homopolymers showed narrow polydispersities of appr. 1.1. Sequential addition polymerizations showed evidence for transesterification (not seen in homopolymerizations) if BL or CL are introduced after a lactide block.

Des catalyseurs Ru supporté sur TiO2 actifs et sélectifs pour l’hydrogénation de l’acide lévulinique en γ-valérolactone en présence d’acide formique comme source interne d’hydrogène ont été développés. L’élaboration d’un nouveau support, TiO2 modifié par Ca2+, permet d’améliorer la production de γ-valérolactone, grâce à la fois à une décomposition de l’acide formique plus sélective en hydrogène et à une hydrogénation de l’acide lévulinique plus efficace. Ces performances améliorées sont associées à l’existence d’interactions Ru/support plus fortes avec une adsorption du CO plus faible, et à une basicité accrue du support. Elles ont été exaltées par la mise en œuvre d’une synthèse photo-assistée sous lumière solaire comme alternative soutenable à l’imprégnation par voie humide, permettant d’obtenir des particules sub-nanométriques de distribution de taille étroite. Il a été montré qu’un profile de type volcano centré sur 1.5 nm relie l’activité catalytique à la taille des particules. / Active and selective Ru catalysts based on TiO2 supports have been developed for the combined hydrogenation of levulinic acid to γ-valerolactone with internal hydrogen supply via in-situ formic acid decomposition. A controlled modification of the TiO2 support by Ca2+ improved the catalytic performance in the one-pot hydrogenation, as a result of enhanced performances in both the formic acid dehydrogenation and the levulinic acid hydrogenation. The improved performances were associated to stronger Ru/support interactions with weaker CO adsorption, as well as to an increased support basicity. The performances were further exalted thanks to a one-step solar light photon-assisted synthesis method used as sustainable alternative to classical wet impregnation. It enabled the uniform dispersion of sub-nanometric metallic Ru particles with narrow distribution and fine size monitoring, and a volcano-type profile centered at 1.5 nm was demonstrated between the nanoparticle size and the activity.

Des ligands diketimines porteurs de substituants N-benzyl, N-9-anthrylmethyl et N-mesitylmethyl (nacnacBnH, nacnacAnH, and nacnacMesH) ont été synthétisés par condensation d’une amine et d’acétyl acétone ou son monoacétal d’éthylène glycol. La chlorination de la position 3 a été effectuée à l’aide de N-chlorosuccinimide conduisant à la formation des ligands ClnacnacBnH et ClnacnacAnH. Cette même position 3 a également été substituée par un groupement succinimide par lithiation du nacnacBnH, suivi de la réaction avec le N-chlorosuccinimide (3-succinimido-nacnacBnH). Les ligands N-aryl nacnacippH et nacnacNaphH (ipp = 2-isopropylphenyl, Naph = 1-naphthyl) ont été préparés selon les procédures reportées dans la littérature. La réaction de ces ligands avec Zn(TMSA)2 (TMSA = N(SiMe3)2) conduit à la formation des complexes nacnacAnZn(TMSA) et ClnacnacBnZn(TMSA). La protonation avec l’isopropanol permet l’obtention des complexes nacnacAnZnOiPr et ClnacnacBnZnOiPr. La réaction avec Mg(TMSA)2 permet quant à elle la formation des complexes nacnacAnMg(TMSA), nacnacMesMg(TMSA), ClnacnacBnMg(TMSA) et ClnacnacAnMg(TMSA). La protonation subséquente à l’aide du tert-butanol permet l’obtention du nacnacMesMgOtBu et du ClnacnacBnMgOtBu, alors que l’on observe uniquement une décomposition avec les ligands possédant des substituants N-anthrylmethyl. La réaction de ces diketimines avec Cu(OiPr)2 conduit aux dimères hétéroleptiques [nacnacBnCu(μ-OiPr)]2 et [3-Cl-nacnacBnCu(μ-OiPr)]2 lors de l’usage des ligands stériquement peu encombrés. Lors de l’utilisation de ligands plus encombrés, la stabilisation du complexe hétéroleptique par dimérisation n’est plus possible, conduisant, par un échange de ligand, à la formation des complexes homoleptiques Cu(nacnacipp)2 et Cu(nacnacNaph)2. Les complexes homoleptiques Cu(nacnacBn)2 et Cu(3-succinimido-nacnacBn)2 ont été obtenus à partir des ligands N-benzyl. Les ligands encore plus encombrés tels que nacnacAnH, nacnacMesH ou ceux comportant des substituants N-methylbenzyl ne présentent alors plus de réactivité avec le Cu(OiPr)2. La plupart des complexes ont été caractérisés par Diffraction des Rayons X. Les complexes homoleptiques ainsi que ceux de TMSA sont monomériques, alors que ceux formés à partir d’alkoxides se présentent sous forme de dimères à l’état solide. Tous les complexes d’alkoxides ainsi que les nacnacAnMg(TMSA)/BnOH et ClnacnacAnMg(TMSA)/BnOH présentent une réactivité modérée à haute en matière de polymérisation du rac-lactide (90% de conversion en 30 secondes à 3 heures). Le nacnacAnZnOiPr permet la synthèse d’un polymère hautement hétérotactique (Pr = 0.90) quand le ClnacnacBnMgOtBu/BnOH génère un polymère isotactique à -30°C (Pr = 0.43). Tous les autres catalyseurs produisent des polymères atactiques avec une légère tendance hétérotactique (Pr = 0.48 – 0.55). Les complexes hétéroleptiques [nacnacBnCu(μ-OiPr)]2 et [3-Cl-nacnacBnCu(μ-OiPr)]2 se révèlent être de très bons catalyseurs pour la polymérisation du rac-lactide présentant une conversion complète du monomère à température ambiante, en solution, en 0,5 à 5 minutes. Le [nacnacBnCu(μ-OiPr)]2 est actif en présence ou absence d’isopropanol, agissant comme agent de transfert de chaine à haute activité (k2 = 32 M–1•s–1) dans le dichlorométhane. Dans l’acétonitrile, le THF, le dichloromethane et le toluène, [nacnacBnCu(μ-OiPr)]2 conduit à une étroite polydispersité, possédant respectivement des kobs = 2.4(1), 5.3(5), 3.6-4.4 and 10(1) min–1. Aucune réaction parasite, telle qu’une trans-esterification, une épimerisation ou une décomposition du catalyseur, n’a été observée. Les complexes homoleptiques en présence d’alcool libre semblent présenter un équilibre avec une petite quantité de leurs équivalents hétéroleptiques, permettant une polymérisation complète, en moins de 60 min, à température ambiante. Tous les catalyseurs de cuivre présentent un haut contrôle de la polymérisation avec une polydispersité égale ou inférieure à 1.1. Les polymères obtenus sont essentiellement atactiques, avec une légère tendance à l’hétérotacticité à température ambiante et -17°C. Le [nacnacBnCu(μ-OiPr)]2 polymérise également la -butyrolactone (BL), l’-caprolactone (CL) et la -valerolactone (VL) avec des constantes respectivement égales à kobs = 3.0(1)•10–2, 1.2–2.7•10–2, et 0.11(1) min–1. Les homopolymères présentent une étroite polydispersité d’approximativement 1.1. Les polymérisations par addition séquentielle ont mis en évidence une trans-estérification (non observée dans les homopolymérisations) si BL ou CL sont introduits après un bloc lactide. / Diketimine ligands bearing N-benzyl, N-9-anthrylmethyl and N-mesitylmethyl substituents (nacnacBnH, nacnacAnH, and nacnacMesH) were prepared from condensation of amine with either acetyl acetone or its ethylene glycol monoketal. Chlorination of the 3-position was achieved using N-chlorosuccinimide, yielding ClnacnacBnH and ClnacnacAnH. The 3-position was also substituted by succinimido by lithiation of nacnacBnH followed by reaction with N-chlorosuccinimide (3-succinimido-nacnacBnH). N-aryl ligands nacnacippH and nacnacNaphH (ipp = 2-isopropylphenyl, Naph = 1-naphthyl) were prepared from literature. The ligands were reacted with Zn(TMSA)2 (TMSA = N(SiMe3)2) to yield nacnacAnZn(TMSA) and ClnacnacBnZn(TMSA). Protonation with isopropanol gave nacnacAnZnOiPr and ClnacnacBnZnOiPr. Reaction of the diketimines with Mg(TMSA)2 afforded nacnacAnMg(TMSA), nacnacMesMg(TMSA), ClnacnacBnMg(TMSA) and ClnacnacAnMg(TMSA). Subsequent protonation with tert-butanol produced nacnacMesMgOtBu and ClnacnacBnMgOtBu, but only decomposition was observed with N-anthrylmethyl substituents. Reaction of the diketimines with Cu(OiPr)2 yielded the heteroleptic [nacnacBnCu(μ-OiPr)]2 and [3-Cl-nacnacBnCu(μ-OiPr)]2 when using sterically undemanding ligands. When sterically more demanding diketimines were used, stabilization of the heteroleptic complex by dimerization was not possible, resulting in the formation of the homoleptic complexes Cu(nacnacipp)2 and Cu(nacnacNaph)2 by ligand exchange. Homoleptic complexes were also prepared with N-benzyl ligands, i. e. Cu(nacnacBn)2 and Cu(3-succinimido-nacnacBn)2. Even bulkier ligands such as nacnacAnH, nacnacMesH or N-methylbenzyl substituents failed to react with Cu(OiPr)2. Most complexes were characterized by single crystal X-ray diffraction. TMSA complexes and homoleptic complexes were monomeric, alkoxide complexes were dimeric in the solid state. All alkoxide complexes, as well as nacnacAnMg(TMSA)/BnOH and ClnacnacAnMg(TMSA)/BnOH were moderately to highly active in rac-lactide polymerization (90% conversion in 30 sec to 3 h). nacnacAnZnOiPr produced highly heterotactic polymer (Pr = 0.90), ClnacnacBnMgOtBu/BnOH produced slightly isotactic polymer at –30 °C (Pr = 0.43), all other catalysts produced atactic polymers with a slight heterotactic bias (Pr = 0.48 – 0.55). Heteroleptic complexes [nacnacBnCu(μ-OiPr)]2 and [3-Cl-nacnacBnCu(μ-OiPr)]2 are very highly active rac-lactide polymerization catalysts, with complete monomer conversion at ambient temperature in solution in 0.5 – 5 min. [nacnacBnCu(μ-OiPr)]2 specifically polymerized in the presence or absence of isopropanol as a chain-transfer reagent with very high activity (k2 = 32 M–1•s–1), in methylene chloride. While in acetonitrile, THF, dichloromethane and toluene has a kobs = 2.4(1), 5.3(5), 3.6-4.4 and 10(1) min–1, respectively. [nacnacBnCu(μ-OiPr)]2 yields narrow polydispersities and no evidence of side reactions such as transesterification, epimerization or catalyst decomposition. The homoleptic complexes in the presence of free alcohol, seem to be in equilibrium with small amounts of the respective heteroleptic complex, which are sufficient to complete polymerization in less than 60 min at room temperature. All Cu catalysts show high control of polymerization with polydispersities of 1.1 and below. The obtained polymers were essentially atactic, with a slight heterotactic bias at ambient temperature and at –17 °C. [nacnacBnCu(μ-OiPr)]2 polymerizes -butyrolactone (BL), -caprolactone (CL) and -valerolactone (VL) with rate constants of kobs = 3.0(1)•10–2, 1.2–2.7•10–2, and 0.11(1) min–1, respectively. Homopolymers showed narrow polydispersities of appr. 1.1. Sequential addition polymerizations showed evidence for transesterification (not seen in homopolymerizations) if BL or CL are introduced after a lactide block.

The isothermal crystallization and melting temperatures of poly(ε-caprolactone) were correlated using fast differential scanning calorimetry. The melting kinetics was found to be independent of isothermal crystallization temperature and time. The conventional Hoffman-Weeks method could not be used to determine the equilibrium melting temperature because the observed melting temperatures were greater than the crystallization temperatures by a constant, so the Gibbs-Thomson method was used instead, yielding an equilibrium melting temperature of 103.4 ± 2.3°C. A modification was proposed to the non-linear Hoffman-Weeks equation that included a non-linear undercooling dependence for the kinetic fold surface free energy upon crystallization and permitted accurate modeling of the observed melting behavior. The isothermal crystallization rates of four narrow molecular weight poly(ethylene oxide) fractions were characterized using fast differential scanning calorimetry for crystallization temperatures spanning 100°C range with the lower limit approaching the glass transition. A transition from homogeneous to heterogeneous primary nucleation was observed at −5°C. The kinetic analysis suggested that the crystal growth geometry depends strongly on temperature, where rod-like structures begin to appear near the glass transition temperature, highly branched solid sheaves grow throughout the homogeneous primary nucleation temperature range, and spherulites grow in the heterogenous primary nucleation range. Poly(δ-valerolactone) was synthesized using microwave-assisted techniques. Narrow molecular weight fractions were obtained using successive precipitation fractionation. Preliminary isothermal crystallization studies suggest that conventional thermal analysis methods are not adequate to measure the melting temperatures accurately due to reorganization during heating. / Doctor of Philosophy / Plastics may be classified into two general categories: those which form ordered domains upon solidification, i.e. undergo crystallization, and those which remain disordered upon solidification, i.e. form glasses. This work is focused on studying the crystallization and melting processes in two linear polymers, poly(ε-caprolactone) and poly(ethylene oxide), using new experimental technology. In the case of poly(ε-caprolactone), the experimental data could not be rationalized by existing theories, and we have proposed modifications to these theories that explained the results. In the case of poly(ethylene oxide), the application of new experimental technology resulted in previously unreported data that indicated novel behavior at very low crystallization temperatures. In the last portion of this work, poly(δ-valerolactone) was made using a novel approach. Conventional experimental approaches to measuring the crystallization and melting behavior were shown to be inadequate.