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[pt] A injeção química, principalmente de surfactantes, é um dos métodos mais utilizados na recuperação melhorada de petróleo. Uma das principais limitações deste método é a perda devido à partição do surfactante para o óleo presente no reservatório. O estudo do equilíbrio de partição água-óleo de formulações de surfactantes torna-se relevante devido a perda existente nos reservatórios, afetando a inviabilidade econômica e ambiental da aplicação. O objetivo deste trabalho foi determinar o coeficiente de partição de surfactantes entre as fases água e óleo através de diferentes métodos analíticos. Foram estudados os surfactantes dodecilbenzeno sulfonato de sódio (SDBS, de tipo aniônico) e o polioxietileno (9- 10) p-teroctil fenol (Triton X-100, de tipo não iônico), e foi utilizado hexadecano como óleo modelo. Com o objetivo de identificar qual seria o melhor procedimento para a quantificação dos surfactantes na fase aquosa e, por conseguinte determinar o coeficiente de partição, foram desenvolvidas três metodologias de quantificação utilizando diferentes técnicas (medidas de tensão interfacial, medidas de absorbância UV-Vis e HPLC com detecção UV). Testes iniciais de solubilidade mostraram que o SDBS é praticamente insolúvel em presença de sal, pelo qual só foram realizados experimentos com este surfactante, em ausência de sal. Para ambos os surfactantes os resultados mostraram uma baixa partição para a fase oleosa, tanto na ausência quanto na presença de sal. Em algumas soluções foi identificada a formação de emulsões devido à concentração do surfactante e a proporção água/óleo utilizada, o qual interferiu com o método espectrofotométrico. Adicionalmente, se estabeleceu uma comparação entre os resultados obtidos pelas metodologias desenvolvidas que permitiram identificar que o melhor dos métodos estudados para a avaliação do equilíbrio de partição foi a cromatografia líquida de alta eficiência (HPLC). A partir destes resultados, pode-se concluir que os surfactantes estudados possuem um baixo valor de coeficiente de partição para a fase óleo, tornando o método de injeção química favorável para a recuperação avançada de petróleo. / [en] Chemical injection, mainly of surfactants, is one of the most used methods for improved oil recovery. One of the main limitations of this method is the loss due to partitioning of the surfactant into the oil present in the reservoir. The study of the water-oil partition balance of surfactant formulations becomes relevant due to the existing loss in the reservoirs, affecting the economic and environmental unfeasibility of the application. The objective of this work was to determine the partition coefficient of surfactants between the water and oil phases using different analytical methods. The surfactants sodium dodecylbenzene sulfonate (SDBS, anionic type) and polyoxyethylene (9-10) p-teroctyl phenol (Triton X-100, nonionic type) were studied, and hexadecane was used as model oil. In order to identify which would be the best procedure for the quantification of surfactants in the aqueous phase and, therefore, to determine the partition coefficient, three quantification methodologies were developed using different techniques (interfacial tension measurements, UV-Vis absorbance measurements, and HPLC with UV detection). Initial solubility tests showed that SDBS is practically insoluble in the presence of salt, so experiments with this surfactant were only carried out in the absence of salt. For both surfactants, the results showed a low partition for the oil phase, both in the absence and in the presence of salt. In some solutions, the formation of emulsions was identified due to the surfactant concentration and the water/oil ratio used, which interfered with the spectrophotometric method. In addition, a comparison was established between the results obtained by the developed methodologies, which allowed to identify that the best method for the evaluation of the partition equilibrium was the high performance liquid chromatography (HPLC). From these results, it can be concluded that the studied surfactants have a low partition coefficient for the oil phase, making the chemical injection method favorable for advanced oil recovery.

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Cancer is currently the second most common cause of death in the world. Despite tremendous progress in the treatment of different forms of cancer, the five year survival rates for lung, colorectal, breast, prostate, pancreatic and ovarian cancers remain quite low. New therapies are urgently needed for the better management of these diseases. In this context, both therapeutic gene and drug delivery constitute promising approaches for cancer treatment and are addressed in this thesis. Focusing on gene delivery, we are proposing the use new pyridinium amphiphiles for obtaining gene delivery systems with improved stability and efficiency and low toxicity (Chapters 2 and 3). The main focus was on pyridinium gemini surfactants (GSs), which possess a soft charge, a high charge/mass ratio and a high molecular flexibility - all key parameters that recommend their use in synthetic gene delivery systems with in vitro and in vivo efficiency. In Chapter 2, we optimized a novel DNA delivery systems through interfacial engineering of pyridinium GS at the level of linker, hydrophobic chains and counterions. In Chapter 3, we tested the effects of blending pyridinium cationic GS into pyridinium cationic lipid bilayers and we have evaluated these blends towards plasmid DNA compaction and delivery process. We have also correlated the cationic bilayer composition with the dynamics of the DNA compaction process, and with transfection efficiency, cytotoxicity and internalization mechanism of resulted nucleic acid complexes. Toward improved drug delivery systems, we introduced new amphiphilic block copolymers synthesized from biocompatible and biodegradable segments. Although their capabilites for loading, transport and release of lipophilic substances stored in their hydrophobic cores are widely known, their stability in vivo is limited due to rapid degradation by esterases present in the body. In Chapter 4, we examined the possibility to increase the enzymatic stability of PEG-PCL macromolecular amphiphiles through interfacial engineering, in a process which separates the hydrophilic/hydrophobic interface from the degradable/non-degradable block interface. We evaluated the stability, toxicity, drug loading and release properties of these new polymers using docetaxel as a model chemotherapeutic drug. The results revealed how hydrophilic/ hydrophobic interface tuning can be used to adjust key properties of polymeric drug delivery systems of this type. / Pharmaceutical Sciences

The increase in microbial resistance to antibiotics underscores the need for novel antibacterial surfaces, particularly for silicone-based implants, because the hydrophobicity of silicones has been linked to undesirable microbial adhesion and biofilm formation. Unfortunately, current strategies for mitigation, such as pretreatment of surfaces with antiseptics/antibiotics, are not consistently effective. In fact, they can facilitate the prevalence of resistant pathogens by exposing bacteria to sublethal concentrations of biocides. Therefore, scientific interest has shifted to preventing initial adhesion (prior to surface colonization) by using surfactants as surface modifiers. Accordingly, Chapter 2 studied the bioactivity of ACR-008 UP (an acrylic-terminated superwetting silicone surfactant) after it was copolymerized in increasing weight percentages with butyl methacrylate (BMA) and/or methyl methacrylate (MMA). Interestingly, copolymers of 20 wt % ACR showed at least 3x less adhesion by Escherichia coli BL21 (E. coli) than any other formulation. This was not a consequence of wettability, which followed a parabolic function with ACR concentration: high contact angles (CA) with sessile water drops were observed at both low (< 20 wt %) and high (> 80 wt %) concentrations of ACR in materials. The CA at 20 wt % ACR was 66°. The lack of E. coli adhesion was ascribed to surfactant-membrane interactions; hence, the antibacterial potential of compounds related to ACR was further probed. Chapter 3, therefore, examines the structure-activity relationships of nonionic silicone polyether surfactants in solution. Azide/alkyne click chemistry was used to prepare a series of eight compounds with consistent hydrophilic tails (8- 44 poly(ethylene glycol) units), but variable hydrophobic heads (branched silicones with 3-10 siloxane linkages, and in two cases phenyl substitutions). The compounds were tested for toxicity at 0.001 w/v %, 2.5 w/v % and their critical micelle concentrations (CMCs), against different concentrations of E. coli in a 3-step assay. Surfactants with smaller head groups had as much as 4x the bioactivity of larger analogues, with the smallest hydrophobe exhibiting potency equivalent to SDS. Smaller PEG chains were similarly associated with higher potency. This data suggests that lower micelle stability, and the theoretically enhanced permeability of smaller silicone head groups in membranes, is linked to antibacterial activity. The results further demonstrate that the simple manipulation of nonionic silicone polyether structures, leads to significant changes in antibacterial action. To ensure similar results were achievable when such surfactants are immobilized on surfaces, 8 compounds with shorter, ethoxysilylpropyl-terminated PEG chains, and branched or linear hydrophobes, were incorporated into a homemade, room temperature vulcanization (RTV) silicone (Chapter 4). The materials, containing 0- 20 wt% surfactants) were then tested for contact killing and cytophobicity against the same E. coli strain. Elastomers modified with 0.5- 1 wt% of (EtO)3Si-PEG- laurate, and separately (EtO)3Si-PEG-tBS, were on average 2x more hydrophilic relative to controls (103°) and differed in their wettability by ~40°, yet both were anti-adhesive; a ~30-fold reduction in adhesion was seen on modified surfaces relative to the control PDMS. Additionally, the (EtO)3Si-PEG-tBS surface demonstrated biocidal behavior, which further highlighted the importance of surfactant chemistry- not just wettability- in observing a specific antibacterial response (if any). Based on the data collated from each Chapter, silicone surfactants seem to have great potential as bioactive agents and warrant further systematic investigations into their mechanisms of action. In so doing, their chemistry may be optimized against different microbes for a variety of applications. In particular, their potential to create non-toxic, cytophobic silicones is particularly encouraging, given the need for anti-adhesive, biofilm preventing material surfaces. / Thesis / Doctor of Philosophy (PhD)

Le but de ce travail est de faire l'étude des mécanismes de calcination sous air et de dégradation sous atmosphère inerte d'un copolymère à trois blocs de type EOxPOyEOx (x = 20, y = 70) dans un matériau mésostructuré de type SBA-15. Les matériaux de type SBA-15 ont été synthétisés selon la méthode de Zhao et al. à une température hydrothermique de 80 °C [2]. Deux différentes extractions dans l'éthanol et l'éthanol acidifié ont été effectuées afin d'obtenir des matériaux ayant des teneurs en agent tensioactif résiduel différentes. Les propriétés physicochimiques des matériaux ont été obtenues par volumétrie d'azote à 77 K, analyse élémentaire du carbone, spectroscopie infrarouge à transformée de Fourier et par résonnance magnétique nucléaire du 13C. Les différentes étapes de dégradation de l'agent tensioactif ont été déterminées à l'aide de l'analyse thermogravimétrique et de la combustion en température programmée identifiée par spectrométrie de masse. Les résultats démontrent que sous les deux types de courants gazeux, l'élimination de la phase organique s'effectue par une fragmentation du polymère libérant successivement les mésopores primaires et les micropores. Par contre, sous atmosphère inerte, cette libération successive des différents types de porosité peut être facilement identifiée par spectrométrie de masse, ce qui en fait un outil de caractérisation prometteur pour les matériaux à paroi poreuse.

Two-dimensional (2D) nanoscale confinement effects on poly(ε-caprolactone) (PCL) crystallization were probed through crystallization studies of PCL-b-poly(tert-butyl acrylate) (PCL-b-PtBA) copolymers, PCL with bulky tri-tert-butyl ester endgroups (PCL triesters), PCL with triacid end groups (PCL triacids), and magnetic nanoparticles stabilized by PCL triacid (PCL MNPs) at the air/water (A/W) interface. Thermodynamic analyses of surface pressure-area per monomer (Π−A)) isotherms for the Langmuir films at the A/W interface showed that PCL-b-PtBA copolymers, PCL triheads and PCL MNPs all formed homogenous monolayers below the dynamic collapse pressure of PCL, Π_C ~11 mN•m⁻¹. For compression past the collapse point, the PCL monolayers underwent a phase transition to three-dimensional (3D) crystals and the nanoscale confinements impacted the PCL crystalline morphologies. Studies of PCL-b-PtBA copolymers revealed that the morphologies of the LB-films became smaller and transitioned to dendrites with defects, stripes and finally nano-scale cylindrical features as the block length of PtBA increased. For the case of PCL triester, irregularly shaped crystals formed at the A/W interface and this was attributed to the accumulation of bulky tert-butyl ester groups around the crystal growth fronts. In contrast, regular, nearly round-shaped lamellar crystals were obtained for PCL triacids. These morphological differences between PCL triacids and PCL triesters were molar mass dependent and attributed to differences in dipole density and the submersion of carboxylic acid groups in the subphase. Nonetheless, enhanced uniformity for PCL triacid crystals was not retained once the polymers were tethered to the spherical surface of a PCL MNP. Instead, the PCL MNPs exhibited small irregularly shaped crystals. This nano-scale confinement effect on the surface morphology at the A/W interface was also molar mass dependent. For the small molar mass PCL MNPs, two layers of collapsed nanoparticles were observed. In a later chapter, studies of polyethylene glycol (PEG) surfactant adsorption onto phospholipid bilayers through quartz crystal microbalance with dissipation monitoring (QCM-D) measurements revealed a strong dependence of the adsorption and desorption kinetics on hydrophobic tail group structure. PEG surfactants with a single linear alkyl tail inserted and saturated the bilayer surface quickly and the surfactants had relatively fast desorption rates. In contrast, PEG lipids, including dioleoyl PEG lipids and cholesterol PEGs, demonstrated slower adsorption and desorption kinetics. The interactions of Pluronics and Nonoxynol surfactants with phospholipid bilayers were also studied. Pluronics showed no apparent affinity for the phospholipid bilayer, while the Nonoxynol surfactants damaged the lipid bilayers as PEG chain length decreased. / Ph. D.

This research evaluated the influence of concentration and surface tension (γ) of aqueous solutions of a non-ionic surfactant on the barrier effectiveness of a fabric containing microporous polypropylene (PP) film that may be used in pesticide protective clothing (PPC). Aqueous solutions of Triton® X-100, a non-ionic surfactant, at various concentrations were prepared, and the γ of each solution was determined. The immediate advancing contact angles (θ), made by a 5-<i>μ</i>L drop of each test liquid on the test fabric, were measured. Barrier effectiveness was evaluated from the capillary penetration, wicking, and wetting characteristics of the fabric using the surfactant solutions at various concentrations. Wetting characteristics were evaluated from the drop absorbency test, a modified Draves test, the spreading coefficient (S_c) values and, by inference, from a Zisman plot. As surfactant concentration increased, γ decreased, and then remained relatively steady past the 0.0134 percent concentration level, the critical micelle concentration (CMC) of Triton® X-100. As Triton® X-100 concentration increased, θ decreased, even past the CMC. Results of the study indicate that, as surfactant concentration increases, the amount of capillary penetration and the wicking distance increase even past the CMC. The time for drop absorbency and the Draves wetting tests were very high (> 600 seconds) for all liquids below CMC. Beyond the CMC, drop absorbency times were significantly lower for solutions of 2.0 and 5.0 percent concentration, and the Draves wetting times were also significantly lower. The values of the cos θ and the γ were used to calculate the S_c for each liquid. The calculated spreading coefficients indicate that the liquids at all concentrations did not spread (wet) on the micro-porous PP test fabric for the advancing θ measured within 10 seconds of placing the drop. Results of the statistical analysis showed that surfactant concentration was a significant factor in determining the barrier effectiveness of the fabric tested. Even though γ remained relatively unchanged beyond the CMC of the surfactant, the inability of the test fabric to serve as an effective barrier against liquid penetration by capillary action, wicking, and wetting increased significantly. Surface energy terms, that are normally used to explain liquid transport and wetting phenomena, may not in themselves be sufficient to determine the effectiveness of a fabric for PPC, especially since concentration of the surfactant, a pesticide adjuvant, is a significant factor in determining the barrier effectiveness of PPC. Consideration must be made for the fact that very high concentrations of surfactants are routinely used in pesticide application. / Master of Science

Aqueous film-forming foam (AFFF) used for fuel firefighting contains polyfluoroalkyl substances (PFAS) that have been identified as environmentally persistent and bioaccumulative resulting in phase out of AFFF. Currently, there are no environmentally friendly foams available that can perform at the same level as AFFF. Fuel transport has been recognized as a potential mechanism behind poor fire extinguishment, but the key features are yet unidentified. To fill these knowledge gaps, identifying the properties and features of surfactants used in firefighting foam that will prevent the transport of liquid fuel through the surfactant solution was imperative. To achieve that, this research was performed exclusively on single surfactants that have applications in firefighting foam. Impact of single surfactants on fuel transport was evaluated. Thermodynamics of the interaction between single surfactants and fuel; and kinetics of fuel transport through single surfactant solutions was observed. It was hypothesized that the liquid fuel transport would influence microstructure in the bulk of the surfactant solution. Experiments were conducted for different single surfactant structures. Various methods were applied to identify the microstructure and interfacial properties of surfactants with and without exposure to liquid fuel. The factor affecting microstructure, identified through this study was further used to evaluate the firefighting performance of single surfactants through ignition test. The thermodynamics of the interaction between fuel and single surfactants helped us to understand the fuel transport mechanism and role of micelle on fuel transport. Surfactant and fuel interaction has been studied below, at, and above the critical micelle concentration of surfactants. The effect of surfactant concentration, convection, and surfactant types were observed on the fuel transport. Moreover, an ignition test was conducted to evaluate the firefighting performance of single surfactants for various fuel types. Overall, the findings from this study will help design a new type of superefficient, environmentally acceptable surfactant for firefighting foam application. / Doctor of Philosophy / Aqueous film-forming foam (AFFF) used for fuel firefighting contains fluorinated compounds which are environmentally persistent and bioaccumulative. Therefore, AFFF has been phased out. There are no environmentally friendly foams available as efficient as current AFFF. Researchers have found that fuel transport through surfactant foam solution is the reason for foam collapse and poor fire extinguishment performance. However, the key parameters affecting fuel transport through foam solution have not been identified. Therefore, new formulations have become challenging, and it is important to identify the parameters affecting fuel transport through the firefighting foams. Surfactants are the key components of firefighting foam. The liquid fuel transport affects the microstructure of the surfactants in the bulk solution. Through this research microstructural and interfacial properties of single surfactants have been studied with and without exposure to liquid fuel. The factors affecting microstructure and firefighting performance of surfactants have been identified. Moreover, the interaction between fuel and single surfactants has been evaluated. The effect of surfactant concentration and fuel type on fuel transport has been observed. Moreover, the effect of convection (at the foam-fuel interface) on fuel transport has been observed. Overall, an understanding of factors affecting fuel transport of firefighting foam is achieved through this research, which can guide new types of efficient, environmentally friendly surfactant design.