L'étude des fluides complexes présente un grand intérêt de par la richesse des phénomènes que font intervenir leur écoulement. Une étude de rhéologie locale de systèmes de micelles géantes en microcanal droit est effectuée. L'expérience montre que les propriétés du fluide soumis à un fort gradient de contrainte ne peuvent être décrites que par une équation rhéologique comportant des termes non locaux. Nous montrons alors l'influence du système de micelles géantes, du confinement ainsi que de la nature des surfaces du microcanal sur ces effets non locaux. Une étude des phénomènes temporels intervenant dans ces écoulements en microcanaux est alors proposée, ainsi qu'une étude préliminaire concernant les écoulements dans des milieux poreux modèles.

Des copolymères à blocs de type ABA à gradient de composition, s'auto-assemblent en micelles sphériques, dans un solvant apolaire sélectif pour les blocs latéraux. Ces solutions micellaires constituent un très bon exemple de la formation de phases vitreuses dans les suspensions colloïdales, en présence d'interactions attractives. Les structures et les dynamiques à l'équilibre et sous cisaillement sont étudiées par diffusion des rayons X, rhéologie et diffusion de la lumière. A faible concentration, les solutions se comportent comme des suspensions de sphères dures et les variations de la viscosité newtonienne, en fonction de la température et de la concentration, peuvent être décrites par une courbe universelle. A des concentrations plus élevées, des forces attractives à courte portée apparaissent qui affectent la formation du verre et sont responsables de l'existence d'un régime viscoélastique. Cette phase a de nombreux points communs avec un gel faible mais peut solidifier lorsqu'un cisaillement supérieur à une valeur critique est appliqué. Cette gélification sous cisaillement de solutions micellaires attractives est différente du rhéo-épaississement qui se produit dans les suspensions colloïdales conventionnelles et dans les « shake-gels ». Les verres qui se forment aux concentrations plus élevées peuvent être de nature attractive ou répulsive en fonction de la force des interactions attractives à courte portée, qui peut être modifiée en variant la température. Les verres répulsifs présentent les dynamiques lentes et les phénomènes de vieillissement qui sont associés aux dynamiques vitreuses classiques.

For more than 70 years, understanding of the mechanism of particle nucleation in emulsion polymerization has been one of the most challenging issues in heterophase polymerization research. Within this work a comprehensive experimental study of particle nucleation in emulsion polymerization of styrene at 70 °C and variety of conditions has been performed. To follow the onset of nucleation, on-line conductivity measurements were applied. This technique is highly sensitive to the mobility of conducting species and hence, it can be employed to follow aggregation processes leading to particle formation. On the other hand, by recording the optical transmission (turbidity) of the reaction mixture particle growth was followed. Complementary to the on-line investigations, off-line characterizations of the particle morphology and the molecular weight have been performed. The aim was to achieve a better insight in the processes taking place after starting the reaction via particle nucleation until formation of colloidally stable latex particles. With this experimental protocol the initial period of styrene emulsion polymerization in the absence as well as in the presence of various surfactants (concentrations above and below the critical micellization concentration) and also in the presence of seed particles has been investigated. Ionic and non-ionic initiators (hydrophilic and hydrophobic types) have been applied to start the polymerizations. Following the above algorithm, experimental evidence has been obtained showing the possibility of performing surfactant-free emulsion polymerization of styrene with oil-soluble initiators. The duration of the pre-nucleation period (that is the time between starting the polymerization and nucleation) can be precisely adjusted with the initiator hydrophobicity, the equilibration time of styrene in water, and the surfactant concentration. Spontaneous emulsification of monomer in water, as soon as both phases are brought into contact, is a key factor to explain the experimental results. The equilibration time of monomer in water as well as the type and concentration of other materials in water (surfactants, seed particles, etc.) control the formation rate and the size of the emulsified droplets and thus, have a strong influence on the particle nucleation and the particle morphology. One of the main tasks was to investigate the effect of surfactant molecules and especially micelles on the nucleation mechanism. Experimental results revealed that in the presence of emulsifier micelles the conductivity pattern does not change essentially. This means that the presence of emulsifiers does not change the mechanism of particle formation qualitatively. However, surfactants assist in the nucleation process as they lower the activation free energy of particle formation. Contrary, seed particles influence particle nucleation, substantially. In the presence of seed particles above a critical volume fraction the formation of new particles can be suppressed. However, micelles and seed particles as absorbers exhibit a common behavior under conditions where monomer equilibration is not allowed. Results prove that the nucleation mechanism comprises the initiation of water soluble oligomers in the aqueous phase followed by their aggregation. The process is heterogeneous in nature due to the presence of monomer droplets. / Polymere dominieren unsere Welt. Die natürlich vorkommenden Polymeren, wie Proteine, Polynukleotide, und Polysaccharide, sind nötig um das Leben zu erhalten. Ebenso wichtig sind die kommerziell erhältlichen Makromoleküle. Beides sind Bausteine, um Materialien zu konstruieren, welche man in beiden Welten finden kann- der natürlichen und der „Mensch-gemachten“ Welt. Unter den verschiedenen Polymerisationsmethoden hat sich die Emulsions-polymerisation zu einem weit verbreiteten Prozess entwickelt. Die Emulsionspolymerisation ist ein einzigartiger Polymerisationsprozess, bei dem ein Monomer oder ein Gemisch von Monomeren in einem wässrigen Medium polymerisiert wird. Dabei entsteht eine Dispersion von Polymeren, welche auch als Latex bezeichnet wird. Derzeit werden mehrere Millionen Tonnen von synthetischen Latices mit Hilfe der Emulsionspolymerisation hergestellt. Diese finden zum Beispiel Verwendung als synthetische Gummi, Latexschaum, Latexfarben, Papierbeschichtungen und Klebstoffen. Außerdem findet man sie auch bei Spezialanwendungen, wie Diagnosetests, Pharmakotherapien und chromatographischen Trennmethoden. Trotz der Vielzahl von industriellen Anwendungen, sollten all jenen, die sich mit Emulsionspolymerisation beschäftigen, den wissenschaftlichen und technologischen Herausforderungen, die sich stellen, bewusst sein. Die wichtigsten Fragen beim Umgang mit der Emulsionspolymerisation beinhalten das Verständnis des Prozesses der Partikelbildung und des Partikelwachstums. Die vorliegende Dissertation beschäftigt sich mit der Frage der Keimbildungs-etappe in Emulsionspolymerisationen. Die Untersuchungen wurden mit Hilfe eines on-line Leitfähigkeitsmessverfahren sowie einigen off-line analytischen Experimenten durchgeführt. Basierend auf den klaren experimentellen Daten, wurde ein besserer Einblick in die tatsächlichen Zustände des Polymerisationssystems, von der Zeit der neu geboren Kerne bis zu endgültig stabilisierten Teilchen, gewonnen.

The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios. / In den letzten Jahrzehnten war die Herstellung von komplizierten Polymerstrukturen ein wichtiges Forschungsthema für Polymerchemiker. Diese Arbeit behandelt die Synthese von (Blockco-)Polymere, die Herstellung von komplexen und stimulus-responsiven Aggregaten (Mizellen) durch Selbstorganisation, sowie die Vernetzung dieser Strukturen. Auch die Anordnung dieser Mizellen zu Aggregaten mit höherer Ordnung wurde untersucht. Zum Beispiel wird die Bildung von Poly(2-oxazolin) basierter Mizellen in wässriger Lösung und die gleichzeitige Funktionalisierung und Vernetzung dieser Mizellen mittels Thiol-In-Chemie beschrieben. Durch die Einführung von pH-responsiven Gruppen in den Kern der Mizellen konnte der Einfluss von geladenen Gruppen im Kern auf das gesamte Aggregat untersucht werden. Das Einführen von Ladung führt zum Quellen des Mizellkerns und damit zu einer niedrigeren lokalen Konzentration von wasserlöslichem Poly(2-ethyl-2-oxazolin) (PEtOx). Diese niedrigere Konzentration ergibt eine Verschiebung des Trübungspunkt dieses Typ I thermoresponsiven Polymers zu höheren Temperaturen. Wenn die Ausdehnung des Kerns nicht erfolgt, z.B. in Anwesenheit einer hohen Salzkonzentration, findet dieser Effekt nicht statt. Ähnliche Strukturen können mithilfe von Mizellen mit komplexen Koazervatkern (English: Complex Coacervate Core Micelles, C3Ms) durch die Interaktion zwischen Polymeren mit negativ und positiv geladenen Blöcken hergestellt werden. Der Vorteil dieser Strukturen ist, dass zwei verschiedene stabilisierende Polymerblöcke in einem Aggregat vereint werden können, was zur Bildung einer Vielzahl noch komplizierterer Strukturen und zu mehr Responsivität führen kann. Mithilfe von Blockcopolymeren, bestehend aus jeweils einen polyionischen Block und einem neutralen Block (z.B. PEtOx, PEO oder poly(N-isopropylacrylamid) (PNIPAAm)), konnten C3Ms hergestellt werden, in denen zwei neutrale Polymere vereint wurden. Es konnte gezeigt werden, dass diese Polymere sowohl gemischt als auch phasensepariert vorliegen können (letzteres ergibt Janus Mizellen), abhängig welche Polymere gewählt werden. Durch Vernetzung im Kern konnten die Mizellen stabilisiert und fixiert werden (C5Ms). Die Selbstanordnung dieser vernetzten Mizellen zu größeren Aggregaten wurde untersucht. Wenn eine Lösung mit vernetzten Mizellen über den Trübungspunkt von PNIPAAm erhitzt wurde, bildeten sich Netzwerke aus Mizellen mit einer gemischten Korona, während Janus Mizellen sich zu wohldefinierten Aggregaten höherer Ordnung anordneten. Weiterhin konnte gezeigt werden, dass Janus Mizellen sich auf der Oberfläche von anorganischen Nanopartikeln anlagern können; z.B. durch die selektive Wechselwirkung zwischen PEO und Silica oder durch die Adsorption von Thiolgruppen auf Gold-Nanopartikeln. Asymmetrische Aggregate konnten auch mithilfe des Streptavidin-Biotin Komplexes erhalten werden. Durch das Binden der Biotin-Endgruppen eines dreiarmigen Sternpolymeren an eine Streptavidin-Einheit und anschließende Belegung der verbliebenen Bindungsstelle mit der Biotin-gruppe eines Homopolymers, können sehr spezifisch zwei verschiedene Polymere in einem Janus Aggregat vereint werden. Auch die Vernetzung des Streptavidins kann erzielt werden, indem andere Mischverhältnisse gewählt werden.

The research presented in this dissertation involves the synthesis, characterization, and application of novel anionic and cationic chiral molecular micelles in capillary electrophoresis (CE) for the separation of diverse chiral compounds. Chapter 1 presents brief overview of the surfactants, micelle polymer, CE and micellar electrokinetic chromatography (MEKC). Chapter 2 describes the simultaneous enantioseparation of eight single chiral center â-blockers using two novel leucine and isoleucine based polymeric surfactants. The simultaneous enantioseparation of multichiral center bearing â-blockers, nadolol and labetalol is described in chapter 3. A synergistic approach, using a combination of polysodium N-undecenoxycarbonyl-L-isoleucinate (poly-L-SUCIL) and sulfated â-CD showed dramatic enantioseparation of four stereoisomers of nadolol. On the other hand for labetalol, enantiomeric separation remains unaffected using the dual chiral selector system. Chapter 4 deals with the enantiomeric separation of the binaphthyl derivatives that was found to be influenced by pH, type and concentration of the background electrolyte as well as concentration of the polymeric surfactant. In chapter 5, characterization of five alkenoxy leucine-based surfactants with variations in chain length (C8-C11), polymerization concentration and degree of polymerization showed significant effects on the chiral resolution and efficiency of hydrophobic â-blockers. The synthesis and characterization of two positively charged amino acid derived chiral ionic liquids (ILs) and their corresponding polymers is presented in chapter 6. Chiral separation of two acidic analyte (difficult to resolve with anionic micelles) can be achieved with both monomers and polymers of ILs. In chapter 7, the synthesis and detailed characterization of three pH independent amino acids derived (L-leucinol, L-isoleucinol and L-valinol) sulfated chiral polymeric surfactants is presented. These chiral sulfated surfactants are thoroughly characterized and the morphological behavior of polymeric sulfated surfactants is revealed using cryogenic high-resolution electron microscopy. The work clearly demonstrates for the first time the superiority of chiral separation in MEKC coupled to mass spectrometry at low pH. Finally, in chapter 8, six amino acid derived chiral surfactants with carboxylate and sulfate head groups were compared for enantioseparation of broad range of structurally diverse racemic compounds at neutral and basic pH conditions.

Micellar electrokinetic chromatography (MEKC) and capillary electrochromatography (CEC) are two of the major capillary electrophoresis (CE) modes that have been interfaced to mass spectrometry (MS) for sensitive and selective analysis of chiral compounds. This research combines these two modes and expands their applications in chiral CE analysis. Chapter 1 is a review of amino acid based molecular micelles used in MEKC-MS for enantioselective analysis over the past five years. In this chapter, a typical MEKC-MS experiment setup as well as detailed standard operating procedure in synthesis of molecular micelles and running a typical MEKC-MS experiment using the molecular micelles is discussed. Chapter 2 described a multivariate MEKC-MS optimization for the simultaneous analysis of two negatively charged model chiral compounds in negative ion mode with molecular micelles. In this chapter, a central composite design (CCD) is used to first construct a series of experiments to optimize all the important MEKC-MS parameters. Next, response surface methodology (RSM) was used to analyze the interactions between the factors, picking up the best separation and detection conditions, predicting the result of the chiral separation/MS detection, and finally running the actual experiment and comparing the chromatographic results with the predicted parameters. Chapter 3 demonstrates a similar multivariate MEKC-MS optimization for analysis of a positively charged model chiral compound in a positive ion mode. The same CCD and RSM methods were used to optimize the separations and MS sensitivity. Chapter 4 describes a chiral analysis of four neutral benzoin derivatives (hydrobenzoin, benzoin, benzoin methyl ether, and benzoin ethyl ether) using MEKC coupled to atmospheric pressure photo-ionization mass spectrometry (APPI-MS). The same multivariate experimental design strategy was used to optimize the MEKC as well as APPI-MS parameters. Simultaneous chiral separation of all four benzoin derivatives was achieved with high detection sensitivity compared to UV-detection. Chapter 5 introduces a novel one-pot synthesis scheme for an acryloyl-terminated, carbamate-linked surfactant-bound monolith with leucine head group and different chain lengths. The method promises to open up the discovery of new amino acid based polymeric monoliths for chiral separations and enhanced chemoselectivity for simultaneous chiral separations and enhanced detection in CEC and CEC-MS. In Chapter 6, five amide-linked surfactant-bound monoliths with different chain lengths and head groups (leucine, valine, and phenylalanine) were synthesized and characterized. Enantioseparation of several test compounds was achieved by CEC using the monolithic columns. One of the chiral surfactant, sodium 11-acrylamidoundecanoyl-L-leucinate (SAAUL), was polymerized in aqueous solution under 60Co radiation to form molecular micelle poly-SAAUL. MEKC experiments were carried out with the poly-SAAUL molecular micelle to separate ten cationic chiral compounds. The result was compared with the CEC separation using the AAUL monolithic column. This study is the first comparison of chiral CEC and MEKC with the same surfactant monomer, which has the capability of forming both chiral stationary phase for CEC and chiral pseudophase for MEKC.

Recently there has been a great deal of attention in the oilfield industry focused on the phenomenal properties of viscoelastic surfactants (VES). The interest is motivated by their applications as switchable smart fluids, their surface tension, and their thickening and rheology enhancement in aqueous solution. Surfactant molecules in solution are known for their ability to assemble spontaneously into complex structures. Under certain thermodynamic conditions, temperature and electrolyte concentrations, wormlike micelles are formed. These micelles share similar equilibrium and dynamic properties with polymer solutions, However, micellar chains can break and recombine spontaneously which make them part of the more general class of living polymers. It is vital to understand the properties of viscoelastic wormlike micelles with regard to their flow in porous media. The overall objective of this study is to establish a better understanding of counterion effect on behavior of VES. The dependence of macroscopic properties on intermolecular interactions of complex fluid systems such as VES is an enormous challenge. To achieve our objective, we use first-principle calculations and molecular dynamics (MD) simulations to resolve the full chemical details in order to study how the structure of the micellar and solution properties depends on the chemical structure of the surfactant head group (HG) and type of counterion. In particular, we run simulations for different structures in gas-phase and aqueous solutions together with their salt counterions at room temperature and atmospheric pressure. For this purpose, we consider four types of surfactant HG (anionic, cationic, betaine and amidoamine oxide) together with the most common ions present in the acidizing fluid of a carbonate reservoir such as Ca2+, Mg2+, Fe2+, Fe3+, Mn2+ and Zn2+, Cl-, OH- and HS-. Hydration of ions as well as interactions with surfactant the HG are studied using density functional theory (DFT). The results give important insight into the links between molecular details of VES HG structure and observed solution properties. This study proposes for the first time the possible mechanisms that explain the exotic behavior of VES at high Fe(III) concentration. Also, our MD simulation suggests that distribution of chloride ion around surfactant molecules is responsible for their viscosity behavior in HCl solution. We believe that our results are an important step to develop more systematic procedures for the molecular design and formulation of more effective and efficient VES systems.

In this study, we evaluated the potential of water-in-oil microemulsions for the separation of beta-galactosidase (lactase) from other proteins. The ability of beta-galactosidase to break down the milk carbohydrate lactose gives the enzyme considerable commercial importance. The extent of solubilization of a commercial Kluyveromyces lactis preparation of beta-galactosidase into microemulsion droplets formed from 200 mM bis (2-ethylhexyl) sodium sulfosuccinate (AOT) in isooctane was measured as a function of buffer type, pH, ionic strength, and protein concentration. Our results showed that, due to the large molecular weight of beta-galactosidase (MW~ 220-240 kDa, dimeric form), the enzyme was taken up by the microemulsion droplets mainly under very low salt conditions. Based on these results, we designed a one-step separation procedure, in which a small volume of aqueous buffer containing the protein mixture is added to an organic surfactant solution. Microemulsion droplets form in the oil and capture protein impurities of smaller molecular weights, while excluding the high molecular weight target protein. This causes the beta-galactosidase to be expelled into a newly formed aqueous phase. The feasibility of this one-step process as a bioseparation tool was demonstrated on a feed consisting of an equal mixture of beta-galactosidase and the test protein beta-lactoglobulin. Recovery and separation of the two proteins was analyzed as function of buffer type, pH, ionic strength, and protein concentration. Results showed that separation was most complete at 100 mM KCl salt concentration, where the droplets were big enough to carry beta-lactoglobulin but too small for lactase. At 100 mM salt concentration, we recovered 92% of the total lactase activity in a virtually pure form. The same separation scheme was then tested on crude extract obtained from a cell culture broth of the yeast Kluyveromyces lactis. Cells of the yeast K. lactis were disrupted by minibeadbeater, forming a crude extract that was used as the feed in our separation process. A 5.4-fold purification factor of the extract was achieved, with 96% activity recovery. The results showed our one-step separation process to be an interesting method for the production of beta-galactosidase as a technical enzyme: it has the potential to achieve a continuous, large-scale partial purification of the enzyme, potentially reducing the number of steps required in downstream process.

Thèse de doctorat : Chimie : Nancy 1 : 2000. / 2000NAN10008. Titre provenant de l'écran-titre.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 166-173). Available also in a digital version from Dissertation Abstracts.