In this thesis extensions to the formalism of endoreversible thermodynamics for multi-extensity fluxes and chemical reactions are introduced. These extensions make it possible to model a great variety of systems which could not be investigated with standard endoreversible thermodynamics. Multi-extensity fluxes are important when studying processes with matter fluxes or processes in which volume and entropy are exchanged between subsystems. For including reversible as well as irreversible chemical reaction processes a new type of subsystems is introduced - the so called reactor. It is similar to endoreversible engines, because the fluxes connected to it are balanced. The difference appears in the balance equations for particle numbers, which contain production or destruction terms, and in the possible entropy production in the reactor. Both extensions are then applied to an endoreversible fuel cell model. The chemical reactions in the anode and cathode of the fuel cell are included with the newly introduced subsystem -- the reactor. For the transport of the reactants and products as well as the proton transport through the electrolyte membrane, the multi-extensity fluxes are used. This fuel cell model is then used to calculate power output, efficiency and cell voltage of a fuel cell with irreversibilities in the proton and electron transport. It directly connects the pressure and temperature dependencies of the cell voltage with the dissipation due to membrane resistance. Additionally, beside the listed performance measures it is possible to quantify and localize the entropy production and dissipated heat with only this one model. / In dieser Arbeit erweitere ich den Formalismus der endoreversiblen Thermodynamik, um Flüsse mit mehr als einer extensiven Größe sowie chemische Reaktionsprozesse modellieren zu können. Mit Hilfe dieser Erweiterungen eröffnen sich zahlreiche neue Anwendungsmöglichkeiten für endoreversible Modelle. Flüsse mit mehreren extensiven Größen sind für die Betrachtung von Masseströmen ebenso nötig wie für Prozesse, bei denen sowohl Volumen als auch Entropie zwischen zwei Teilsystem ausgetauscht werden. Für sowohl reversibel wie auch irreversibel geführte chemische Reaktionsprozesse wird ein neues Teilsystem - der "Reaktor" - vorgestellt, welches sich ähnlich wie endoreversible Maschinen durch Bilanzgleichungen auszeichnet. Der Unterschied zu den Maschinen besteht in den Produktions- bzw. Vernichtungstermen in den Teilchenzahlbilanzen sowie der möglichen Entropieproduktion innerhalb des Reaktors. Beide Erweiterungen finden dann in einem endoreversiblen Modell einer Brennstoffzelle Anwendung. Dabei werden Flüsse mehrerer gekoppelter Extensitäten für den Zustrom von Wasserstoff und Sauerstoff sowie für den Protonentransport durch die Elektrolytmembran benötigt. Chemische Reaktionen treten in der Anode und Kathode der Brennstoffzelle auf. Diese werden mit dem neu eingeführten Teilsystem, dem Reaktor, eingebunden. Mit Hilfe des Modells werden dann Wirkungsgrad, Zellspannung und Leistung einer Brennstoffzelle unter Berücksichtigung der Partialdrücke der Substanzen, der Temperatur sowie der Dissipation beim Protonentransport berechnet. Dabei zeigt sich, dass experimentelle Daten für die Zellspannung sowohl qualitativ als auch näherungsweise quantitativ durch das Modell abgebildet werden können. Der Vorteil des endoreversiblen Modells liegt dabei in der Möglichkeit, mit nur einem Modell neben den genannten Kenngrößen auch die abgegebene Wärme sowie die Entropieproduktion zu quantifizieren und den einzelnen Teilprozessen zuzuordnen.

Ce travail porte sur le développement d’une technique de calorimétrie sans contact pour des écoulements diphasiques. Ces derniers sont réalisés sur la forme d’un train gouttes dans des tubes de taille millimétriques dans des supports isopériboliques. L’idée principale est de coupler la Thermographie Infrarouge et les outils microfluidiques pour proposer une technique adapté de mesure. L’utilisation de la microfluidique rend possible l’utilisation de très faibles volumes réactionnels limitant ainsi tout risque lié à la dangerosité des réactions réalisées au sein des gouttes, l’outil Infrarouge permet de suivre ces écoulements avec grande précision. Les résultats de ces travaux de thèse montrent que l’outil est capable d’estimer des propriétés thermo-physiques des écoulements non réactifs. Ainsi, que de caractériser de réactions chimiques en termes d’enthalpie et cinétique. Finalement cette dernière caractérisation a été comparée aux techniques classiques pour mettre en évidence la précision et les avantages de l’outil développé / This work concerns the development of a non-contact calorimeter for two-phase flow characterization. The biphasic flow is performed under a droplet configuration inside millimetric tubings which are inserted into the isoperibolic chip. The main idea is to combine the Infrared Thermography and microfluidic tools to propose a suitable technique for accurate measurements. Microfluidics enables the use of small reaction volumes thus limiting any risk of dangerous reactions inside droplets, the Infrared tool enables to monitor the thermal signature of these flows with high accuracy. The results of this thesis show that this tool is able to estimate the thermophysical properties of non-reactive flows. Also , it is possible to characterize chemical reactions in terms of enthalpy and kinetics . Finally the latter characterization was compared to conventional techniques to demonstrate the benefits and the precision of the tool.

Cálculos usando métodos de estrutura eletrônica (Hartree-Fock, Mõller-Plesset de segunda ordem e DFT, B3LYP) foram efetuados pelo programa Gaussian98 em microcomputadores e estações de trabalho, com o objetivo de elucidar os canais de decomposição unimolecular de éter dietílico em fase gasosa e foram comparados com valores obtidos através de aproximações baseadas na mecânica estatística pela metodologia de Benson. O éter dietílico vem sendo usado como um aditivo para o óleo diesel e combustível alternativo e o conhecimento de suas vias vias de decomposição é fundamental nestas investigações. Dezesseis modos primários, do qual, quatro ocorrem através de cisão de ligações simples C-O, C-C,C(1)-H e C(2)-H e doze ocorrendo através de estados de transição cíclicos, os quais eliminam produtos como hidrogênio etano, acetaldeído, etano, álcool etílico, metil etil éter, metano, alguns carbenos e também di-radicais, foram considerados para a determinação das barreiras de ativação, entalpias de reação, entropias de reação e energia livre de Gibbs de reação. Vias primárias ocorrendo através de cisão de ligação, não reproduziram os valores experimentais para as barreiras de ativação, mas reproduziram de modo significante, valores da entalpia da reação. Eliminação de eteno e álcool etílico, ocorrendo através de um estado de transição de quatro centros, apresentou a barreira de ativação mais baixa. Acetaldeído e eliminação de etano, ocorrendo através de quatro centros, apresentou barreira significativamente alta, mas por outro lado, a menor entalpia, ligeiramente exotérmica por -0,8 kcal.mol-1. Eliminações 1,2 de metano e carbeno ocorrendo através de três centros, junto com a eliminação 1, 1 de hidrogênio e carbeno por três centros, eliminação 2,2 hidrogênio e carbeno por três centros e eliminação 1,4 de hidrogênio, acetaldeído e eteno por seis centros, apresentaram barreiras de ativação relativamente próximas mostrando que elas são competitivas entre si. Os valores computados dos canais que ocorrem por estados de transição cíclicos foram comparados com os resultados experimentais disponíveis e discutida a validade desta abordagem computacional para o estudo de reações unimoleculares de multi-canais. Determinação de parâmetros termoquímicos, como calor de formação para espécies radicalares dos canais de decomposição primário e alguns radicais alcóxidos, junto com a estimativa de afinidade eletrônica e protônica (com a abordagem ab initio Gaussian 2 a qual estima energias eletrônicas muito precisas) foram efetuados e seus resultados foram comparados com os valores experimentais disponíveis e valores obtidos através de energias de ligação e da regra de aditividade de Benson. / Calculations using methods of electronic structure(Hartree-Fock, second order Moller-Plesset and DFT: B3LYP) had been effected through the Gaussian98 program in microcomputers and workstations, with the objective to elucidate the unimolecular decomposition channels of diethyl ether in gaseous phase. These results also had been compared to those obtained by the methodology based in statistical mechanics through Benson\'s approach. Sixteen primary ways, which, four occur through the break of simple bonds C-O, C-C,C(1)-H, C(2)-H, and twelve occur through cyclical transistion states, which eliminate products as hydrogen, ethene, acetaldehyde, ethane, ethyl alcohol, methyl ethyl ether, methane, some carbenes and also diradicals. These products had been considered to the determination of the activation barriers, enthalpies of reaction, entropies of reaction and free energy of Gibbs of reaction. Primary ways occurring through the break of bonds, had not reproduced experimental values for the activation barriers, however they had reproduced in a significant way, values of the enthalpy of the reaction. Elimination of ethene and ethyl alcohol, occurring by a transition state of four centers, presented the lowest activation barrier. Acetaldehyde and ethane elimination occurring through four centers, presented a high significantly barrier, but on the other hand it presented the smallest enthalpy, lightly exothermic above -0,8 kcal.mol-1. Eliminations 1,2 of methane and carbene occurring through three centers, together with the elimination 1,1 of hydrogen and carbene through three centers, elimination 2,2 of hydrogen and carbene through three centers and elimination 1,4 of hydrogen, acetaldehyde and ethene through six centers, had presented relatively next activation barriers, showing that they are competitive among themselves. The computed values of the channels that occur through cyclical transition states had been compared with the available experimental results and the trustworthiness of this computational boarding for the study of unimolecular reactions in multi-channel had been dicussed. Determination of thermochemical parameters, as heat of formation for radicalar species of the primary channel of decomposition and some alcoxyde radicais, together with the estimative of the electronic and protonic affinities,( with the ab initio Gaussian 2 boarding which estimate very precise eletronic energies ) and their results had been compared with the available experimental values and with values gotten through energies of bond and Benson\'s additivity rule.

This thesis contains investigations in two different areas, described under six chapters. Chapter 1 contains a broad introduction to the area of foldamers, while Chapters 2, 3, 4, and 5 deal with various novel classes of synthetic polymers which can form folded structures in solution utilizing different non-covalent interactions. Chapter 6 deals with a distinctly different topic, where the objective was to study the effect of phenyl ring location on the micellization properties of a series of isomeric cationic surfactants. Synthetic polymers typically adopt a random coil conformation in solution, which is primarily an entropy driven process. So the generation of well-defined secondary structures in synthetic polymers requires specific intra-chain inter-segment interactions that will give adequate enthalpic contribution to overcome the entropic penalty associated with the formation of well-ordered conformations. During the past decade, various research groups have made significant effort to understand the essential design elements that could enable secondary structure formation in synthetic macromolecules through intra-chain inter-segment interactions, such as hydrogen bonding, solvophobic and solvophilic interaction, acid-base interaction, bond angle constraint, steric interaction, charge-transfer interaction, metal-ion complexation etc.1 Gellman2 first used the term “foldamer” to describe “any polymer with a strong tendency to adopt a specific compact conformation” which was more precisely defined by Moore and coworkers3 as “any oligomer that folds into a conformationally ordered state in solution, the structures of which are stabilized by a collection of non-covalent interactions between nonadjacent monomer units” and where the folded conformation is one of the various possible conformations. Several classes of foldamers have been studied during the past decade; a majority of them are well-defined oligomers that possess relatively restricted conformational degrees of freedom. Relatively fewer studies have explored conformational control in flexible high molecular weight polymers that possess greater conformational freedom.4 A few years ago, Ghosh et al. designed a polymeric system wherein charge-transfer interactions between alternatively placed electron-rich and electron-deficient aromatic units, aided by metal-ion complexation and solvophobic interactions, causes the polymer chain to adopt a specific folded conformation.5 Such charge-transfer induced folding was first studied by Iverson and co-workers6 in well-defined oligomers and was later elaborated by Zhao et al.7 to generate alternate designs to fold oligomeric systems. In all these studies, the C-T interactions served not only to assist the folding process but it also served as a valuable spectroscopic signature to study the folding process. The objectives of the present study are to develop simple synthetic strategies to generate different types of polymers that could be fold in solution using various noncovalent interactions. We have developed a simple synthetic strategy to design a new type of donor (1,5-dialkoxynaphthalene-DAN) containing polymer that carries a tertiary amine unit in the spacer segment, which could interact strongly with a suitably designed acceptor (pyromellitic diimide-PDI) bearing folding agent that carries a carboxylic acid group, as shown in Scheme 1.8 This acid-base interaction, brings the acceptor unit in a suitable position so as to form a C-T complex with the adjacent donors, resulting in the folding of the polymer chain. The folded conformation was studied using UV-vis and NMR spectroscopy and the folding propensities were rationalized using DFT studies. The highest association constant between the folding agent and the polymer was estimated to be around 1200 M-1. Scheme 1. Schematic representation of folding aided by two-point interactions with a folding agent. This value of association constant was not adequate to realize some potentially interesting properties in solid state. In an attempt to develop alternate systems, that could exhibit stronger propensity to fold, we designed a new type of cationic ionene,9 wherein electron-rich (DAN) and electron-deficient (PDI) aromatic units were included within the alkylene segments in an alternating fashion, as shown in Scheme 2.10 The charge-transfer (C-T) interaction between the donor and acceptor units in neighbouring segments of the ionene not only reinforced the transition to the collapsed nano-bundle form but also provides a useful spectroscopic handle to monitor the conformational change. The UV-visible spectra of these novel D-A ionene solutions at a fixed concentration in four different solvents, namely water, methanol, acetonitrile and DMSO, show different extents of charge-transfer interaction. The colour of the solution in water was deep-red, whereas in acetonitrile, it was light-yellow. The conformational transition could also be induced by titrating an acetonitrile solution of the ionene with increasing amounts of water causing a dramatic increase in the intensity of the charge-transfer band, which reflects the extent of collapse to the zig-zag state that brings the donor and acceptor units together. AFM studies confirmed the presence of flat pancake-like aggregates having nearly constant height of about 3-5 nm, which was in accordance with the estimated thickness of the postulated zig-zag structure. Scheme 2. Schematic depiction of folding of D-A ionene (left), AFM micrograph showing pancake-like aggregates of D-A ionenes (right-top), a line scan depicting the heights and diameters of the aggregates along with a schematic depiction of the aggregate (right-bottom). Scheme 3. Schematic representation of folding aided by interactions with a folding agent. In order to explore this concept further, we designed a two component system wherein the solvophobically-driven collapse of a DAN-containing ionene chain in a polar solvent is reinforced by intercalation with a suitably designed electron-deficient acceptor-containing external folding agent. DAN containing ionene polymer chains in polar solvent form an accordion-type zig-zag structure that brings adjacent donor units in close proximity; this provided an ideal hydrophobic pocket for intercalation of suitably designed electron-deficient acceptor molecules, the additional driving motivation for the intercalation being the formation of a C-T complex as shown in Scheme 3.11 Several acceptor-bearing molecules were prepared by the derivatization of pyromellitic dianhydride and naphthalene tetracarboxylic dianhydride with two different oligoethylene glycol monomethyl ether monoamines. UV-vis spectroscopic studies were carried out by using a 1:1 mixture of the DAN-ionenes and different acceptor molecules in water/DMSO solvent mixtures. The intensity of the charge-transfer (C-T) band was seen to increase with the water content in the solvent mixture, thereby suggesting that the intercalation is indeed aided by solvophobic effects. The naphthalene diimide (NDI) bearing acceptor molecules consistently formed significantly stronger C-T complexes when compared to the pyromellitic diimide (PDI) bearing acceptor molecules, which is a reflection of the stronger π-stacking tendency of the former. The highest association constant between the folding agent and the polymer was estimated to be around 4519 M-1, which was a substantial improvement over the earlier reported values.9 With a slight modification in the pendant group, we designed a water-soluble DAN-containing ionene, which can intercalate hydrophobic electron-deficient molecules, like TNT (2,4,6-trinitrotoluene), within the hydrophobic interstices between DAN units (as shown in Scheme 4), causing a depletion in fluorescence from the DAN units; TNT at concentration as low as 30 nM could be detected in this manner. Scheme 4. Schematic representation of folding of water soluble ionene and interactions with an electron-deficient hydrophobic moiety TNT. Scheme 5. Schematic representation of folded D-A allyl ionene. In light of the growing interest in single-chain polymeric nanoparticles, the fully collapsed D-A ionenes in water could be viewed as polymeric nanoparticles that are stitched together by reversible weak noncovalent interactions. In an attempt to transform the folded structure into a polymeric nanoparticle using covalent bonding, we designed D-A ionene that carries potentially polymerizable allyl units on the cationic head group instead of the dimethyl amine head group that was used in previous examples (as shown in Scheme 5). Preliminary studies showed that polymerization does not proceed readily; however, thiol-ene based clicking strategy enabled partial stitching of the folded segments, by the use of a suitably designed dithiol. In the last section of this thesis, we examined the effect of phenyl ring location on the micellization properties of a series of isomeric cationic surfactants, wherein the phenyl ring location was varied from head to tail region (as shown in Scheme 6).12 Thus, cationic surfactants (S1-S5) bearing a long alkyl chain that carries a 1,4phenylene unit and a trimethyl ammonium headgroup was synthesized and their solution properties were examined. Micellization behavior was studied using conductivity, ITC (Isothermal Titration Calorimetry), SANS (Small-Angle Neutron Scattering) and NMR. These present studies demonstrated that the presence of a large rigid ring near the hydrocarbon tail-end of the surfactant leads to a dramatic change in the micelle structure; the driving motivation to form micelles in such systems is greatly reduced and the micelles that are formed are relatively smaller and contain significantly fewer surfactants. NMR studies of micellar solutions of these surfactants indicate that the variation in the phenyl ring location may also help to probe the microenvironment at various depths within the micellar aggregates. Scheme 6. Structures of the various surfactant molecules carrying the 1,4-dioxyphenylene unit at different locations within hydrophobic segment (left), variation of CMC values (right). References (1) Foldamers - structure, properties, and applications, edited by Stefan Hecht and Ivan Huc, Wiley-VCH, 2007. (2) Gellman, S. H. Acc. Chem. Res. 1998, 31, 173. (3) Hill, D. J.; Mio, M. J.; Prince, R. B.; Huges, T. S.; Moore, J. S. Chem. Rev. 2001, 101, 3893. (4) (a) Wang, W.; Li, L. S.; Helms, G.; Zhou, H. H.; Li, A. D. Q. J. Am. Chem. Soc. 2003, 125, 1120. (b) Li, A. D. Q.; Wang, W.; Wang, L. Q. Chem. Eur. J. 2003, 9, 4594. (c) Neuteboom, E. E.; Meskers, S. C. J.; Meijer, E. W.; Janssen, R. A. J. Macromol. Chem. Phys. 2004, 205, 217. (d) Balbo Block, M. A.; Hecht, S. Macromolecules 2004, 37, 4761. (5) (a) Ghosh, S.; Ramakrishnan, S. Angew. Chem. Int. Ed. 2004, 43, 3264. (b) Ghosh, S.; Ramakrishnan, S. Angew. Chem. Int. Ed. 2005, 44, 5441. (6) Lokey, R. S.; Iverson, B. L. Nature 1995, 375, 303. (7) Zhao, X.; Jia, M. X. Jiang, X. K.; Wu, L. Z.; Li, Z. T.; Chen. G. J. J. Org. Chem. 2004, 69, 270. (8) De, S.; Koley, D.; Ramakrishnan, S. Macromolecules 2010, 43, 3183. (9) Williams, S. R.; Long, T. E. Prog. Polym. Sci. 2009, 34, 762. (10) De, S.; Ramakrishnan, S. Macromolecules 2009, 42, 8599. (11) De, S.; Ramakrishnan, S. Chem. Asian J. 2011, 6, 149. (12) De, S.; Aswal, V. K.; Ramakrishnan, S. Langmuir 2010, 26, 17882. (For structural formula pl see the abstract file.

Le travail réalisé en collaboration entre l’entreprise CNIM et le laboratoire IUSTI a permis la miseen place d’un outil de simulation numérique afin d’étudier à l’échelle locale différents phénomènescouplés qui se produisent dans un réacteur de gazéification en lit fluidisé dense. L’approche choisie,DEM (Discrete Element Method), est basée sur le suivi de paquets de particules. Les résultats desimulation ont été comparés à des mesures expérimentales réalisées dans les laboratoires IUSTIet LERMAB : mesure de pression dans un lit fluidisé peu profond et caractérisation de la réactionde pyrolyse par suivis temporels de la masse volumique par une méthode innovante et de latempérature de la particule de biomasse ainsi que la composition des gaz produits. À plus grandeéchelle, les prédictions numériques du code ont été comparées à des mesures expérimentales deprofil de vitesse des particules et de mélange et ségrégation issues de la littérature. Les résultatsnumériques du lit fluidisé bisolide sans et avec réactions chimiques, obtenus sont en bon accordavec les mesures expérimentales. Ils ont permis de mettre en évidence le fort couplage entre lesphénomènes hydrodynamiques et thermochimiques.Ces travaux ouvrent de nouvelles perspectives tant sur le plan de l’expérimentation que de la simulation numérique où l’approche DEM retenue a montré un fort potentiel. L’extrapolation dumodèle DEM pour la simulation de la gazéification à des réacteurs industriels reste encore un défiau regard des ressources informatiques. / Energy production from green and renewable resources, such as biomass, are currently experiencinga significant growth. Thermochemical conversion of this biomass by gasification is a process usedfor over a century but still requires significant developments in terms of rentability optimizationand quality improvement of products gases.The work carried out in collaboration between the CNIM company and the IUSTI laboratoryallowed the establishment of a numerical simulation tool to study locally different coupled phenomenaoccurring in a dense fluidized bed gasification reactor. The chosen approach, DEM (DiscreteElement Method), is based on the monitoring of particle packets. The simulation results werecompared to experimental measurements realised in IUSTI and LERMAB laboratories : measuringpressure in a shallow fluidized bed and characterization of pyrolysis reaction with the timetracking of particle density by an innovative method, temperature and the composition of theproducts gases. On a larger scale, the numerical code predictions were compared with velocity,particles mixing and segregation profiles from experimental measurements of the literature. Theobtained numerical results of bi-solid fluidized bed with and without chemical reactions are ingood agreement with the experimental measurements. It helped to highlight the strong couplingbetween hydrodynamic and thermochemical phenomena.This work opens up new perspectives on the experimental plan and numerical simulation whichDEM approach has shown great potential. The extrapolation of the DEM model for the simulationof gasification industrial reactors remains a challenge in terms of computer resources.

In verfahrenstechnischen Anlagen der Flüssig-Flüssig-Stoffübertragung kommt es an der Phasengrenze zwischen den nicht mischbaren Flüssigphasen häufig zur Ausbildung hydrodynamischer Instabilitäten. Sie sind mit komplexen Geschwindigkeitsfeldern in den Flüssigphasen, insbesondere in den grenzschichtnahen Regionen verbunden und führen zu einem starken Anstieg der pro Zeiteinheit übertragenen Stoffmenge. Die Lösung der Diffusionsgleichung reicht in diesem Fall zur Vorausberechnung des für Auslegungszwecke bedeutsamen Stoffdurchgangskoeffizienten nicht mehr aus. Chemische Reaktionen stellen Quellen oder Senken von Wärme und Stoff dar, die das Auftreten von Instabilitäten begünstigen und die mathematische Beschreibung zusätzlich erschweren. Im Rahmen der vorliegenden Arbeit wurden experimentelle und numerische Untersuchungen zum Flüssig-Flüssig-Stoffübergang in einem vertikalen Kapillarspalt durchgeführt. Reaktionsfreie Stoffübergänge und solche mit einer exothermen chemischen Reaktion an der Phasengrenze zeigten eine große Vielfalt von Konvektionsstrukturen, wie Rollzellen, Thermiken und das doppeldiffusive Fingerregime. Die Visualisierung der Transportvorgänge erfolgte durch das Schattenschlierenverfahren. Die Beobachtungen wurden hinsichtlich geometrischer Eigenschaften von Konvektionsstrukturen sowie deren zeitlicher Änderung ausgewertet. Dazu zählten insbesondere das Längenwachstum von Thermiken und horizontale Wellenlängen von Fingerstrukturen. Zur mathematischen Beschreibung der Phänomene im Kapillarspalt wurde ein Modell entwickelt, welches auf den gekoppelten, zweidimensionalen Transportgleichungen von Impuls, Wärme und Stoff beruht. Es berücksichtigt dichte- und grenzflächenspannungsgetriebene Instabilitätsmechanismen sowie die besonderen Durchströmungseigenschaften des Kapillarspalts. Die Phasengrenze wurde als eben angenommen. Die Lösung der Modellgleichungen erfolgt auf numerischem Wege durch ein Computerprogramm. Das Modell ist in der Lage, die beobachteten Instabilitätsphänomene qualitativ richtig wiederzugeben. Mit Hilfe von Simulationsrechnungen konnte der Mechanismus aufgeklärt werden, der zum schnelleren Rückgang des Stoffdurchgangskoeffizienten im Rollzellenregime der rein grenzflächenspannungsgetrieben Instabilität im Vergleich zum Vorgang mit überlagerter Dichtekonvektion führt. Des Weiteren gelang der Nachweis des doppeldiffusiven Fingerregimes beim Stoffübergang mit exothermer Grenzflächenreaktion. Die berechnete Erhöhung des Stoffdurchgangskoeffizienten stimmt mit Angaben in experimentellen Arbeiten anderer Autoren überein.

Det här examensarbetet fokuserar på hur man kan kombinera två innehållsaspekter i undervisning med barn i förskolan. Innehållet som bearbetas är naturvetenskap och estetik. Naturvetenskapsdelen i arbetet innefattar kemiska reaktioner och den estetiska delen innefattar drama. Dramat kommer att användas som ett verktyg för att lära om naturvetenskap med fokus på kemiska reaktioner. Studiens insamlingsmetod innefattar filmning och ljudinspelning. Resultatet i studien visar att barnens perspektiv blir synligt genom att barnen får berätta sina tankar om kemiska vätskor. Studiens resultat visar även att ett intresse har väckts bland barnen kring kemiska vätskor och detta lägger en grund för förskollärare att arbeta vidare med och utgå från barnens intresse.

L’objectif de ce travail est de remplacer les catalyseurs organométalliques à base d’étain et de mercure utilisés lors de la synthèse de polyuréthane via la réaction isocyanate – alcool. Une étude bibliographique a montré que la basicité et la nucléophilie d’un catalyseur organique gouvernent son activité et le mécanisme réactionnel qu’il induit. Pour les catalyseurs organométalliques, ces propriétés catalytiques s’expliquent par des considérations électroniques ainsi que par le principe HSAB. D’autre part, une étude approfondie du catalyseur organomercuriel a été menée. Elle a révélé l’intérêt d’ajouter à l’espèce catalytique organométallique un acide carboxylique, de préférence à longue chaîne carbonée. Celui-ci ralentit l’hydrolyse du catalyseur tout en augmentant sa sélectivité envers la réaction isocyanate – alcool. De nouveaux catalyseurs ou systèmes catalytiques originaux ont ensuite été évalués grâce à un test simplifié. Trois catalyseurs organométalliques ont ainsi été sélectionnés pour de nouveaux essais dans des conditions plus proches de celles rencontrées dans l’industrie. Ils se sont tous révélés actifs, mais seul le -dicétonate de zinc II permet d’obtenir un prépolymère incolore et transparent, deux critères essentiels pour les applications visées. Il pourrait donc remplacer le catalyseur organostannique. Enfin, l’étude de la sélectivité de systèmes catalytiques impliquant un catalyseur commercial en présence d’acide néodécanoïque a confirmé le rôle protecteur de ce dernier. La sélectivité du complexe de zinc retenu précédemment a par ailleurs été évaluée et apparaît 2,5 fois supérieure à celle du complexe organomercuriel à remplacer. / The aim of this work is to replace organotin and organomercury catalysts used for the synthesis of polyurethane via the isocyanate – alcohol reaction. A bibliographic review revealed that basicity and nucleophilicity of an organic catalyst affect its activity and the reaction mechanism it induces. For organometallic catalysts, these catalytic properties can be explained by electronic considerations and by the HSAB principle. On the other hand, a comprehensive study of the organomercury catalyst highlighted the benefit to combine it with a carboxylic acid, preferably with a long carbon backbone. This slows down hydrolysis of the catalyst while increasing its selectivity toward the isocyanate – alcohol reaction. New original catalysts or catalytic systems were then evaluated using a simplified experiment. Three organometallic catalysts were selected for further testing in conditions closer to industrial ones. They all showed appropriate catalytic activity, but the zinc II -diketonate is the only one to provide a colorless and transparent prepolymer, two essential criteria for the intended applications. This complex could therefore replace the organotin catalyst. Finally, the study of the selectivity of catalytic systems involving a commercial catalyst in the presence of neodecanoic acid confirmed its protective role toward hydrolysis. The previously retained zinc complex was also evaluated and revealed a selectivity 2.5 times greater than that of the organomercurial complex to replace.

The behavior of the Deoxyribonucleic Acid (DNA) molecule can be exploited to perform useful computation. It can also be ”programmed” using the language of Chemical Reaction Networks (CRNs). One specialized CRN construct is the Surface Chemical Reaction Network (SCRN). The SCRN construct can implement asynchronous cellular automata, which can in turn be used to implement digital logic circuits. SCRN based digital logic circuits are thought to have several advantages over regular CRN circuits. One of these proposed advantages is their scalability. This thesis investigates the scalability of SCRN based adder circuits, how does an increase in the number of bits affect the time required for the circuit to produce a correct result? Additionally, how is the throughput of the circuit affected when multiple additions are performed in a pipelined fashion? These questions are studied through experiments where the execution of optimized SCRN adder circuits is simulated. Due to the stochastic nature of SCRNs each such execution is all but guaranteed to be unique, requiring the simulation of the circuits to be repeated until a sufficiently large statistical sample has been collected. The results show these samples to follow a Gaussian distribution, regardless of the number of bits or the number of pipelined operations. The experiments show the simulated latency of the studied SCRN adder circuits to scale linearly with the number of input bits. The results also show that the throughput can be greatly improved through the pipelining of multiple operations. However, the results are inconclusive as to the maximum possible throughput of SCRN adder circuits. A conclusion of the project is that SCRN digital logic circuit design could conceivably benefit from the implementation of specialized components beyond the standard logic gates. / DNA-molekylen kan utnyttjas för att genomföra användbara beräkningar. Den kan också ”programmeras” via abstraktionen kemiska reaktionsnätverk. Ytbundna Kemiska Reaktionsnätverk (YKR) är i sin tur en vidare specialisering av sådana reaktionsnätverk. Ett YKR kan implementera en asynkrona cellulära automat, som i sin tur kan implementera kretsar för digital logik. Kretsar för digital logik byggda med YKR anses ha flera fördelar gentemot motsvarande kretsar byggda från vanliga kemiska reaktionsnätverk. En av dessa tilltänkta fördelar ligger i deras skalbarhet. Detta examensarbete undersöker skalbarheten hos YKR-baserade additions-kretsar, hur påverkar ett ökat antal bitar tiden som krävs för att kretsen ska producera ett korrekt resultat? Vidare, hur påverkas genomströmningen när flera operationer matas in direkt och genomför efter varandra i en pipeline? Dessa frågor studeras genom experiment där körningar av optimerande YKR-baserade additionskretsar simuleras. På grund av de stokastiska egenskaperna hos YKR är varje sådan körning i princip garanterad att vara unik, vilket kräver upprepade simuleringar av varje krets tills ett tillräckligt stort statistiskt urval har insamlats. Dessa resultat visar sig följa en normalfördelningskurva, oavsett antalet bitar eller antalet operationer som matats in i en pipeline. Experimenten visar att den simulerade latensen skalar linjärt med antalet indata-bitar för de studerade additionskretsarna. Resultaten visar även att genomströmningen förbättras avsevärt när flera operationer körs direkt efter varandra i en pipeline. Resultaten är dock ofullständiga när det gäller uppmätandet av additionskretsarna högsta möjliga genomströmning. En slutsats av projektet är att YKR-baserade kretsar för digital logik möjligen skulle kunna gagnas av implementerandet av specialiserade komponenter utöver de vanliga logikgrindarna.

Biological cells consist of many subunits that form distinct compartments and work together to allow for life. These compartments are clearly separated from each other and their sizes are often strongly correlated with cell size. Examples for those structures are centrosomes, which we consider in this thesis. Centrosomes are essential for many processes inside cells, most importantly for organizing cell division, and they provide an interesting example of cellular compartments without a membrane. Experiments suggest that such compartments can be described as liquid-like droplets. In this thesis, we suggest a theoretical description of the growth phase of centrosomes. We identify a possible mechanism based on phase separation by which the centrosome may be organized. Specifically, we propose that the centrosome material exists in a soluble and in a phase separating form. Chemical reactions controlling the transitions between these forms then determine the temporal evolution of the system. We investigate various possible reaction schemes and generally find that droplet sizes and nucleation properties deviate from the known equilibrium results. Additionally, the non-equilibrium effects of the chemical reactions can stabilize multiple droplets and thus counteract the destabilizing effect of surface tension. Interestingly, only a reaction scheme with autocatalytic growth can account for the experimental data of centrosomes. Here, it is important that the centrioles found at the center of all centrosomes also catalyze the production of droplet material. This catalytic activity allows the centrioles to control the onset of centrosome growth, to stabilize multiple centrosomes, and to center themselves inside the centrosome. We also investigate a stochastic version of the model, where we find that the autocatalytic growth amplifies noise. Our theory explains the growth dynamics of the centrosomes of the round worm Caenorhabditis elegans for all embryonic cells down to the eight-cell stage. It also accounts for data acquired in experiments with aberrant numbers of centrosomes and altered cell volumes. Furthermore, the model can describe unequal centrosome sizes observed in cells with disturbed centrioles. Our example thus suggests a general picture of the organization of membrane-less organelles.:1 Introduction 1.1 Organization of the cell interior 1.2 Biology of centrosomes 1.2.1 The model organism Caenorhabditis elegans 1.2.2 Cellular functions of centrosomes 1.2.3 The centriole pair is the core structure of a centrosome 1.2.4 Pericentriolar material accumulates around the centrioles 1.3 Other membrane-less organelles and their organization 1.4 Phase separation as an organization principle 1.5 Equilibrium physics of liquid-liquid phase separation 1.5.1 Spinodal decomposition and droplet formation 1.5.2 Formation of a single droplet 1.5.3 Ostwald ripening destabilizes multiple droplets 1.6 Non-equilibrium phase separation caused by chemical reactions 1.7 Overview of this thesis 2 Physical Description of Centrosomes as Active Droplets 2.1 Physical description of centrosomes as liquid-like droplets 2.1.1 Pericentriolar material as a complex fluid 2.1.2 Reaction-diffusion kinetics of the components 2.1.3 Centrioles described as catalytic active cores 2.1.4 Droplet formation and growth kinetics 2.1.5 Complete set of the dynamical equations 2.2 Three simple growth scenarios 2.2.1 Scenario A: First-order kinetics 2.2.2 Scenario B: Autocatalytic growth 2.2.3 Scenario C: Incorporation at the centrioles 2.3 Diffusion-limited droplet growth 2.4 Discussion 3 Isolated Active Droplets 3.1 Compositional fluxes in the stationary state 3.2 Critical droplet size: Instability of small droplets 3.3 Droplet nucleation facilitated by the active core 3.4 Interplay of critical droplet size and nucleation 3.5 Perturbations of the spherical droplet shape 3.5.1 Linear stability analysis of the spherical droplet shape 3.5.2 Active cores can center themselves in droplets 3.5.3 Surface tension stabilizes the spherical shape 3.5.4 First-order kinetics destabilize large droplets 3.6 Discussion 4 Multiple Interacting Active Droplets 4.1 Approximate description of multiple droplets 4.2 Linear stability analysis of the symmetric state 4.3 Late stage droplet dynamics and Ostwald ripening 4.4 Active droplets can suppress Ostwald ripening 4.4.1 Perturbation growth rate in the simple growth scenarios 4.4.2 Parameter dependence of the stability of multiple droplets 4.4.3 Stability of more than two droplets 4.5 Discussion 5 Active Droplets with Fluctuations 5.1 Stochastic version of the active droplet model 5.1.1 Comparison with the deterministic model 5.1.2 Ensemble statistics and ergodicity 5.1.3 Quantification of fluctuations by the standard deviation 5.2 Noise amplification by the autocatalytic reaction 5.3 Transient growth regime of multiple droplets 5.4 Influence of the system geometry on the droplet growth 5.5 Discussion 6 Comparison Between Theory and Experiment 6.1 Summary of the experimental observations 6.2 Estimation of key model parameters 6.3 Fits to experimental data 6.4 Dependence of centrosome size on cell volume and centrosome count 6.5 Nucleation and stability of centrosomes 6.6 Multiple centrosomes with unequal sizes 6.7 Disintegration phase of centrosomes 7 Summary and Outlook Appendix A Coexistence conditions in a ternary fluid B Instability of multiple equilibrium droplets C Numerical solution of the droplet growth D Diffusion-limited growth of a single droplet E Approximate efflux of droplet material F Determining stationary states of single droplets G Droplet size including surface tension effects H Distortions of the spherical droplet shape H.1 Harmonic distortions of a sphere H.2 Physical description of the perturbed droplet H.3 Volume fraction profiles in the perturbed droplet H.4 Perturbation growth rates I Multiple droplets with gradients inside droplets J Numerical stability analysis of multiple droplets K Numerical implementation of the stochastic model / Biologische Zellen bestehen aus vielen Unterstrukturen, die zusammen arbeiten um Leben zu ermöglichen. Die Größe dieser meist klar voneinander abgegrenzten Strukturen korreliert oft mit der Zellgröße. In der vorliegenden Arbeit werden als Beispiel für solche Strukturen Zentrosomen untersucht. Zentrosomen sind für viele Prozesse innerhalb der Zelle, insbesondere für die Zellteilung, unverzichtbar und sie besitzen keine Membran, welche ihnen eine feste Struktur verleihen könnte. Experimentelle Untersuchungen legen nahe, dass solche membranlose Strukturen als Flüssigkeitstropfen beschrieben werden können. In dieser Arbeit wird eine theoretische Beschreibung der Wachstumsphase von Zentrosomen hergeleitet, welche auf Phasenseparation beruht. Im Modell wird angenommen, dass das Zentrosomenmaterial in einer löslichen und einer phasenseparierenden Form existiert, wobei der Übergang zwischen diesen Formen durch chemische Reaktionen gesteuert wird. Die drei verschiedenen in dieser Arbeit untersuchten Reaktionen führen unter anderem zu Tropfengrößen und Nukleationseigenschaften, welche von den bekannten Ergebnissen im thermodynamischen Gleichgewicht abweichen. Insbesondere verursachen die chemischen Reaktionen ein thermisches Nichtgleichgewicht, in dem mehrere Tropfen stabil sein können und der destabilisierende Effekt der Oberflächenspannung unterdrückt wird. Konkret kann die Wachstumsdynamik der Zentrosomen nur durch eine selbstverstärkende Produktion der phasenseparierenden Form des Zentrosomenmaterials erklärt werden. Hierbei ist zusätzlich wichtig, dass die Zentriolen, die im Inneren jedes Zentrosoms vorhanden sind, ebenfalls diese Produktion katalysieren. Dadurch können die Zentriolen den Beginn des Zentrosomwachstums kontrollieren, mehrere Zentrosomen stabilisieren und sich selbst im Zentrosom zentrieren. Des Weiteren führt das selbstverstärkende Wachstum zu einer Verstärkung von Fluktuationen der Zentrosomgröße. Unsere Theorie erklärt die Wachstumsdynamik der Zentrosomen des Fadenwurms Caenorhabditis elegans für alle Embryonalzellen bis zum Achtzellstadium und deckt dabei auch Fälle mit anormaler Zentrosomenanzahl und veränderter Zellgröße ab. Das Modell kann auch Situationen mit unterschiedlich großen Zentrosomen erklären, welche auftreten, wenn die Struktur der Zentriolen verändert wird. Unser Beispiel beschreibt damit eine generelle Möglichkeit, wie membranlose Zellstrukturen organisiert sein können.:1 Introduction 1.1 Organization of the cell interior 1.2 Biology of centrosomes 1.2.1 The model organism Caenorhabditis elegans 1.2.2 Cellular functions of centrosomes 1.2.3 The centriole pair is the core structure of a centrosome 1.2.4 Pericentriolar material accumulates around the centrioles 1.3 Other membrane-less organelles and their organization 1.4 Phase separation as an organization principle 1.5 Equilibrium physics of liquid-liquid phase separation 1.5.1 Spinodal decomposition and droplet formation 1.5.2 Formation of a single droplet 1.5.3 Ostwald ripening destabilizes multiple droplets 1.6 Non-equilibrium phase separation caused by chemical reactions 1.7 Overview of this thesis 2 Physical Description of Centrosomes as Active Droplets 2.1 Physical description of centrosomes as liquid-like droplets 2.1.1 Pericentriolar material as a complex fluid 2.1.2 Reaction-diffusion kinetics of the components 2.1.3 Centrioles described as catalytic active cores 2.1.4 Droplet formation and growth kinetics 2.1.5 Complete set of the dynamical equations 2.2 Three simple growth scenarios 2.2.1 Scenario A: First-order kinetics 2.2.2 Scenario B: Autocatalytic growth 2.2.3 Scenario C: Incorporation at the centrioles 2.3 Diffusion-limited droplet growth 2.4 Discussion 3 Isolated Active Droplets 3.1 Compositional fluxes in the stationary state 3.2 Critical droplet size: Instability of small droplets 3.3 Droplet nucleation facilitated by the active core 3.4 Interplay of critical droplet size and nucleation 3.5 Perturbations of the spherical droplet shape 3.5.1 Linear stability analysis of the spherical droplet shape 3.5.2 Active cores can center themselves in droplets 3.5.3 Surface tension stabilizes the spherical shape 3.5.4 First-order kinetics destabilize large droplets 3.6 Discussion 4 Multiple Interacting Active Droplets 4.1 Approximate description of multiple droplets 4.2 Linear stability analysis of the symmetric state 4.3 Late stage droplet dynamics and Ostwald ripening 4.4 Active droplets can suppress Ostwald ripening 4.4.1 Perturbation growth rate in the simple growth scenarios 4.4.2 Parameter dependence of the stability of multiple droplets 4.4.3 Stability of more than two droplets 4.5 Discussion 5 Active Droplets with Fluctuations 5.1 Stochastic version of the active droplet model 5.1.1 Comparison with the deterministic model 5.1.2 Ensemble statistics and ergodicity 5.1.3 Quantification of fluctuations by the standard deviation 5.2 Noise amplification by the autocatalytic reaction 5.3 Transient growth regime of multiple droplets 5.4 Influence of the system geometry on the droplet growth 5.5 Discussion 6 Comparison Between Theory and Experiment 6.1 Summary of the experimental observations 6.2 Estimation of key model parameters 6.3 Fits to experimental data 6.4 Dependence of centrosome size on cell volume and centrosome count 6.5 Nucleation and stability of centrosomes 6.6 Multiple centrosomes with unequal sizes 6.7 Disintegration phase of centrosomes 7 Summary and Outlook Appendix A Coexistence conditions in a ternary fluid B Instability of multiple equilibrium droplets C Numerical solution of the droplet growth D Diffusion-limited growth of a single droplet E Approximate efflux of droplet material F Determining stationary states of single droplets G Droplet size including surface tension effects H Distortions of the spherical droplet shape H.1 Harmonic distortions of a sphere H.2 Physical description of the perturbed droplet H.3 Volume fraction profiles in the perturbed droplet H.4 Perturbation growth rates I Multiple droplets with gradients inside droplets J Numerical stability analysis of multiple droplets K Numerical implementation of the stochastic model