This dissertation addresses two topics associated with the assembly of surfactants at the solid-liquid interface for adsorption and materials synthesis. The first is the adsorption of an anionic fluorinated surfactant, tetraethylammonium perfluorooctylsulfonate (TEA-FOS), at the solid/liquid interface. Attenuated total reflection Fourier transform infrared spectroscopy is used to study the adsorption kinetics and average orientation of surfactants at the hydroxylated germanium surface. Atomic force microscopy provides complementary images of the adsorbed layer structure on mica. The adsorption follows unusual three-stage kinetics in which the rate of adsorption starts fast, slows as the surface becomes crowded, and then (surprisingly) accelerates due to nucleation of a heterogeneous multilayer structure. These fast-slow-fast three stage adsorption kinetics are observed for a wide range of concentrations at pH 6, and the rates of the three stages are modulated by pH and salt by tuning electrostatic interactions among surfactants, counterions, and the surface. The results suggest that tetraethylammonium mediates interactions between surfactants and with negatively charged surfaces. The dichroism measurements and AFM are consistent with a mechanism in which TEA-FOS first forms an incomplete layer with chains oriented randomly or somewhat parallel to the surface, followed by formation of flattened multilayer clusters with the chains oriented somewhat normal to the substrate. The second topic is the sol-gel synthesis of mesoporous silica materials using dual surfactant templates. Studies of templating with mixed cetyltrimethylammonium bromide and octyl-beta-D-glucopyranoside surfactants shows that the ternary phase diagram of surfactants in water can be used to predict mesoporous materials structure, and that vapor-phase ammonia treatments can either stabilize the structure or induce swelling by the Maillard reaction. Studies of sol-gel reaction-induced precipitation with demixed hydrocarbon and fluorocarbon cationic surfactant micelles show a wide variety of pore structures. A number of synthesis parameters are adjusted to tune the pore structure, for instance to adjust the size and populations of bimodal mesopores. Selective swelling of the two surfactants by liphophilic and fluorophilic solvents is observed. Finally, proteinaccessible hollow spherical silica particles with mesoporous shells are reported. The methods for engineering mesoporous materials reported here have potential applications in adsorption, controlled drug delivery and for catalysis.

Surfactant templating provides for the synthesis of ordered mesoporous silica and the opportunity to tailor the pore size, pore structure, particle morphology and surface functionality of the silica through the selection of synthesis conditions and surfactant template. This work extends the synthesis of nanostructured silica using fluorinated surfactant templates to the synthesis of organic/inorganic composites. The effect of fluorinated surfactant templates (C6F13C2H4NC5H5Cl, C8F17C2H4NC5H5Cl and C10F21C2H4NC5H5Cl), which have highly hydrophobic fluorocarbon tails, on functional group incorporation, accessibility, and silica textural properties is examined and compared to properties of hydrocarbon surfactant (C16H33N(CH3)3Br, CTAB) templated silica. Hydrocarbon (vinyl, n-decyl and 3-aminopropyl) and fluorocarbon (perfluoro-octyl, perfluorodecyl) functional group incorporation by direct synthesis is demonstrated, and its effects on silica properties are interpreted based on the aggregation behavior with the surfactant templates. Silica materials synthesized with CTAB possess greater pore order than materials synthesized with the fluorocarbon surfactants. The incorporation of the short vinyl chain substantially reduces silica pore size and pore order. However, pore order increases with functionalization for materials synthesized with the fluorinated surfactant having the longest hydrophobic chain. The incorporation of longer chain functional groups (n-decyl, perfluorodecyl, perfluoro-octyl) by direct synthesis results in hexagonal pore structured silica for combinations of hydrocarbon/fluorocarbon surfactant and functional groups. The long chain of these silica precursors, which can be incorporated in the surfactant micelle core, affect the pore size less than vinyl incorporation. Synthesis using the longer chain fluoro-surfactant (C8F17C2H4NC5H5Cl) template in ethanol/water solution results in highest incorporation of both n-decyl and the fluorocarbon functional groups, with a corresponding loss of material order in the fluorinated material. Matching the fluorocarbon surfactant (C6F13C2H4NC5H5Cl) to the perfluoro-octyl precursor did not show improved functional group incorporation. Higher incorporation of the perfluoro-octyl functional group was observed for all surfactant templates, but the perfluoro-decyl silica is a better adsorbent for the separation of hydrocarbon and fluorocarbon tagged anthraquinones. Incorporating a reactive hydrophilic functional group (3-aminopropyl) suggests further applications of the resulting nanoporous silica. Greater amine incorporation is achieved in the CTAB templated silica, which has hexagonal pore structure; the order and surface area decreases for the fluorinated surfactant templated material.

The use of compressed CO2 processing to alter the pore size, structure and timescale of silica condensation in surfactant templated silica thin films and powders is investigated by systematically varying the template structure and CO2 processing conditions. Tailoring the mesoporous materials increases its potential applications, as demonstrated in catalysis, drug delivery, chromatographic and electrode applications. This work demonstrates for the first time the applicability of fluorinated surfactants as templates for the synthesis of mesoporous silica thin films by dip coating. Well-ordered films with 2D hexagonal close-packed pore structure are synthesized in an acid-catalyzed medium using three cationic fluorinated templates of varied tail length and branching (C6F13C2H4NC5H5Cl, C8F17C2H4NC5H5Cl and (CF3)2CFC5F9C2H4NC5H5Cl). CO2 processing of the fluorinated templated silica results in a significant and controlled increase in pore diameter relative to the unprocessed films. The pore expansion is significantly greater compared to the negligible expansion observed in hydrocarbon (C16H23NC5H5Br) templated silica. The greater swelling of the fluorinated templates is attributed to the favorable penetration of CO2 in the CO2-philic fluorinated tail and the relative solvation of each template is interpreted from their interfacial behavior at the CO2-water interface. The CO2 based pore expansion observed in fluorinated surfactant templated films is extended successfully to base-catalyzed silica powders templated with a fluorinated surfactant (C6F13C2H4NC5H5Cl). Pore expansion in silica powders is significantly less than in acid catalyzed films and demonstrates the effects of pH on surfactant selfassembly in CO2 and increased silica condensation at basic conditions, which inhibits pore expansion. Finally, the use of fluorescence probe molecules is demonstrated for in-situ monitoring of the of CO2 processing of surfactant templated silica films to provide time dependent data on the local environment and dynamics of CO2 penetration. CO2 uptake occurs in surfactant tails even for hydrocarbon templates (C16H23N(CH3)3Br and C16H23NC5H5Br), which display negligible CO2 based swelling of the resulting pores. The timescale of silica condensation increases significantly in the presence of CO2 suggesting opportunities for structure alteration through application of external forces, such as magnetic fields and change in substrate chemistry and system humidity

Self-assembled nonionic alkyl glycoside surfactants are of interest for creating functional adsorption and catalytic sites at the surface of mesoporous metal oxides, but they typically impart poor long-range order when used as pore templates. Improved order and control over the functional site density may be achieved by mixing them with a cationic surfactant. To confirm this hypothesis, we investigate the lyotropic liquid crystalline (LLC) phase behavior of aqueous solutions of the functional nonionic surfactant n-dodecyl β-D-maltoside (C12G2) and cationic cetyltrimethylammonium bromide (C16TAB). A ternary phase diagram of the C16TAB-C12G2-water system is developed at 50 °C. By replacing the volume of water in the phase diagram with an equivalent volume of silica, ordered mesoporous materials are prepared by nanocasting with variable C12G2/C16TAB ratios. Metal oxide mesophases can almost always be predicted from the ternary phase diagram, except that silica prepared with high C12G2/C16TAB ratios are very weakly ordered, perhaps due to differences in hydrogen bonding or rate of assembly. Based on the ternary phase diagram of the system, a systematic approach is taken to the incorporation of titania sites via complexation to the maltoside headgroup of C12G2. Complexation to a saccharide is expected not only to guide titanium to the pore surface, but also to prevent uncontrolled hydrolysis and condensation of the (usually quite reactive) titanium precursor. Tetrahedrally coordinated titanium atoms incorporated into a silica network are believed to be the active oxidation sites required for heterogeneous silica-supported titania oxidation catalysts. To promote well-ordered materials and to allow control over titania site density, the mixed C12G2 / C16TAB system is used for pore templating. Series of Si-Ti mixed oxide thin films and bulk materials are synthesized with different amounts of titanium loading by utilizing pre-complexation between C12G2 and titanium isopropoxide. The degrees of homogeneity (indicated by tetracoordinated Ti) in these films are superior to those of films synthesized with the same loading of titanium but without C12G2 or without pre-complexation. Transition metal-carbohydrate complexation provides highly dispersed, tetrahedrally coordinated titanium atoms rather than the octahedral sites found without saccharide complexation.

Rhamnolipid (RL) biosurfactants have been considered "green" alternatives to synthetic surfactants. Here, systematic studies of monorhamnolipids (mRLs) and their synthetic analogues are performed to characterize their interfacial and solution behaviors as surfactants. Chemical structure-surface activity relationships of rhamnolipids were probed using surface tension measurements on RLs and a series of their synthetic analogues designed by "truncation modification." Based on our study on RLs and the rationally-designed RL analogues, the key structural factor responsible for the excellent surface activity performance of rhamnolipids is the presence of the rhamnose moiety in the headgroup. As a result, rhamnopyranosides (RhEs), the simplest surfactants with a rhamnose moiety in the headgroup, show surface activity comparable to the bioproduced mRLs. The purified mixture of mRLs harvested from Pseudomonas aeruginosa ATCC 9027 was mixed with a nonionic surfactant Tween-20 (TW) and studied by surface tension measurements at pH 8. The experimental values of CMC show deviation from the theoretical values predicted by ideal solution theory, which is hypothesized to be due to a shape change from rod-shaped to spherical as the mole fraction of TW is increased. The hypothesis about the shape change is supported by dynamic light scattering results, regular solution theory, and packing parameter theory. Polarization modulated-infrared reflection-absorption spectroscopy (PM-IRRAS) has been used to characterize the orientation of the synthetic rhamnolipid Rha-C18-C18 at the air-water interface. Although rhamnolipids exhibit pH-dependent micellization, their orientation at the air-water interface is not affected by pH. The average tilt angle of their alkyl chains is determined to be ~45° at a surface pressure π = 40 mN/m which decreases to 36° when Pb²⁺ is present in the subphase. Assisted by molecular modeling, the packing of mRLs at the air-water interface is believed to be dominated by the packing of their large hydrophilic headgroups. Finally, the adsorption isotherm of mRLs on hydrophobic polyethylene surfaces was generated by ATR-FTIR from solutions of different pH, which were then fit to a Frumkin adsorption model to yield the thermodynamic adsorption parameters, the adsorption equilibrium constant and the interaction parameter. mRLs strongly adsorb to d-PE, and the adsorption is pH dependent.

Depuis quelques années, le béton connait une période de mutation. Les tendances actuelles concernant la formulation des bétons à hautes performances et à faibles impacts environnementaux montrent que la fraction volumique solide est de plus en plus élevée. Cette augmentation de la fraction volumique solide est cependant difficilement compatible avec une fluidité importante. La thèse présentée ici a donc pour but de proposer des solutions permettant de contourner le problème de viscosité des ces nouveaux bétons. Nous nous attachons ainsi à identifier les mécanismes d'action de certains polymères à l'origine d'une diminution de la viscosité macroscopique de pâtes de ciment concentrées. Les polymères que nous étudions appartiennent à deux familles différentes : les super plastifiants et les agents entraîneurs d'air. Alors que le chapitre 1 a pour objectif d'expliquer le contexte actuel et de justifier l'intérêt des recherches menées durant cette thèse, le chapitre 2 présente les procédures expérimentales utilisées. Nous proposons des protocoles permettant de faire la distinction entre les effets des polymères étudiés sur la contrainte seuil et leurs effets sur l'autre paramètre du comportement :la viscosité. Dans le chapitre 3, nous mettons en évidence certains mécanismes d'action des polymères adsorbants de type super plastifiants. Nous observons que deux polymères peuvent avoir un effet différent sur la dissipation visqueuse d'une pâte de ciment pour une contrainte seuil donnée. Nous suggérons alors que les molécules de polymère adsorbé modifient l'état de floculation du système, et donc la façon dont le cisaillement se concentre entre les grains. Dans le même temps, les molécules de polymère non adsorbé modifient la viscosité du fluide interstitiel. La viscosité macroscopique résulte alors de la compétition entre ces deux mécanismes. Dans le chapitre 4, nous nous intéressons aux effets des agents entraîneurs d'air. Grâce à des mesures sur pâtes de ciment et mortiers, nous montrons que, suivant la consistance du système étudié, l'entraînement d'air peut diminuer ou non la viscosité. Nous suggérons qu'un tel comportement trouve son origine dans la compétition entre la tension de surface qui tend à empêcher la déformation des bulles et la consistance du système en écoulement qui tend à les déforme

Fractured rock formations represent a valuable source of groundwater and can be highly susceptible to contamination by dense, non-aqueous phase liquids (DNAPLs). The goal of this research is to evaluate the effectiveness of three accepted remediation technologies for addressing DNAPL contamination in fractured rock environments. The technologies under investigation in this study are chemical oxidation, bioremediation, and surfactant flushing. Numerical simulations were employed to examine the performance of each of these technologies at the field scale. The numerical model DNAPL3D-RX, a finite difference multiphase flow-dissolution-aqueous transport code that incorporates RT3D for multiple species reactions, was modified to simulate fractured rock environments. A gridding routine was developed to allow the model to accurately capture DNAPL migration in fractures and aqueous phase diffusion gradients in the matrix while retaining overall model efficiency. Reaction kinetics code subroutines were developed for each technology so as to ensure the key processes were accounted for in the simulations. The three remedial approaches were systematically evaluated via simulations in two-dimensional domains characterized by heterogeneous orthogonal fracture networks parameterized to be representative of sandstone, granite, and shale. Each simulation included a DNAPL release at the water table, redistribution to pools and residual, followed by 20 years of ‘ageing’ under ambient gradient conditions. Suites of simulations for each technology examined a variety of operational issues including the influence of DNAPL type and remedial fluid injection protocol. Performance metrics included changes in mass flux exiting, mass destruction in the matrix versus the fractures, and percentage of injected remedial fluid interacting with the target contaminant. The effectiveness of the three remediation technologies covered a wide range; the mass of contaminants destroyed were found to range from 15% to 99.5% of the initial mass present. Effectiveness of each technology was found to depend on a variety of critical factors particular to each approach. For example, in-situ chemical oxidation was found to be limited by the organic material present in the matrix of the rocks, while the efficiency of enhanced bioremediation was found to be related to factors such as the location of indigenous bacteria present in the domain and rate of bioremediation. In the chemical oxidation study, the efficiency of oxidant consumption was observed to be poor across the suite of scenarios, with greater than 90% of the injected permanganate consumed by natural oxidant demand. This study further revealed that the same factors that contributed to forward diffusion of contaminants prior to treatment are critical to this remediation method as they can determine the extent of contaminant destruction during the injection period. Bioremediation in fractured rock was demonstrated to produce relatively good results under robust first-order decay rates and active microorganisms throughout the fractures and matrix. It was demonstrated that under ideal conditions, of the total initial mass present, up to 3/4 could be reduced to ethene, indicating bioremediation may be a promising treatment approach due to the effective penetration of electron donor into the matrix during the treatment period and the ongoing treatment that occurs after injection ceases. However, when indigenous bacteria was assumed to exist only within the fractured walls of sandstone, it was found that under the same conditions, the rate of dechlorination was 200 times less than the Base Case. Since the majority of the mass resided in the matrix, lack of bioremediation in the matrix significantly reduced the effectiveness of treatment. Surfactant treatment with Tween-80 was proven to be a relatively effective technique in enhanced solubilisation of DNAPL from the fractures within the domain. However, by comparing the aqueous and sorbed mass at the start and end of the Treatment stage, it is revealed that surfactant treatment is not efficient in removing these masses that reside within the matrix. Furthermore, DNAPLs identified in dead end vertical fractures were found to remain in the domain by the end of the simulations across all scenarios studied; indicating that the injected surfactant experiences difficulty in accessing DNAPLs entrapped in dead end fractures. Altogether, the results underscore the challenge of restoring fractured rock aquifers due to the field scale limitations on sufficient contact between remedial fluids and in situ contaminants in all but the most ideal circumstances.

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Les PolyGlycosides d'Alkyle (APGs) sont des agro-tensioactifs dont les propriétés de surface, la biodégradabilité et l'innocuité vis-à-vis de la peau leur offrent de nombreuses applications dans les domaines de la détergence, de la cosmétique et de l'alimentaire. Les APGs sont synthétisés selon la réaction de glycosidation acido-catalysée de Fischer entre un sucre et un accepteur de glycosyle, tel qu'un alcool gras. A l'échelle industrielle, cette voie de synthèse présente plusieurs contraintes liées à la faible solubilité du sucre dans l'alcool lipophile, l'utilisation de pressions réduites et la manutention de catalyseurs acides toxiques et/ou corrosifs. Ces facteurs imposent un équipement spécifique, augmentent les coûts de production et favorisent la dégradation des APGs. Dans un premier temps, les sulfoxydes et les sulfones ont été utilisés comme solvants dans la synthèse d'APGs sans catalyseur et à pression atmosphérique. Cette méthodologie est transposable à de nombreux donneurs et accepteurs de glycosyle. Notre étude a montré que la réaction de glycosidation est catalysée par les acides organiques produits par caramélisation partielle du sucre. La faible solubilité des solvants soufrés dans les alcools gras à température ambiante a été mise à profit dans la mise au point d'un procédé de synthèse d'APGs permettant la récupération et le recyclage de ces solvants. Un milieu réactionnel biphasique décanol - sulfolane a été décrit pour l'obtention d'un rendement en xylosides de décyle supérieur à 80 % en un temps de réaction remarquablement court. La synthèse d'APGs par conversion directe de la biomasse lignocellulosique a fait l'objet de la seconde partie de ce travail. La réaction de transglycosidation du xylane et des hémicelluloses de peuplier a été réalisée sous activation thermique, sans solvant ou en présence de diméthylsulfoxyde, et sous irradiations micro-ondes. L'efficacité de chaque mode d'activation à promouvoir la réaction de transglycosidation a été discutée en fonction de l'origine botanique et de la composition chimique des matières végétales. / Alkyl PolyGlycosides (APGs) are biobased and biodegradable amphiphilics with good surfactant properties and low skin irritability, which are sought in cosmetics, detergents and food. APGs are synthesized by acid-catalyzed Fischer's glycosidation of a carbohydrate source and a glycosyl acceptor such as a long-tailed alcohol. Industrial APGs production suffers from various drawbacks such as the poor solubility of the carbohydrate in the fatty alcohol, the pressure management and the use of toxic or corrosive acid catalysts. Those issues impose more stringent demand on equipment, increase the production costs and favor APGs degradation reactions.Firstly we have been involved in developing an innovative strategy for the catalyst-free synthesis of APGs under atmospheric pressure. Sulfoxides and sulfones have been efficiently used for the manufacture of APGs starting from various glycosyl donors and acceptors. The reaction was induced by organic acids produced by partial carbohydrate caramelisation. Interestingly some of the sulfur-containing solvents were not soluble in fatty alcohols at room temperature whereas the reaction medium was homogenous at the glycosidation temperature. These solvents have been easily recovered and recycled without decrease of APGs yields. A decanol-sulfolane biphasic reaction medium has been designed for the production of decyl-D-xylosides in short reaction times and yields up to 83 %.The second phase of this work was focused on the direct conversion of lignocellulosic materials into APGs. The transglycosidation reaction of xylan and poplar hemicelluloses has been studied under thermal activation, without solvent or in the presence of dimethylsulfoxide, and under microwave irradiations. The efficiency of each activation mode has been discussed as a function of the botanical origin and the chemical composition of lignocellulosic substrates.