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The thin film pressure balance (TFPB) technique were used to study the stability of single foam films produced in the presence of n-alkyl polyoxyethylene (CnEOm) homologues. The results showed that films thin faster than predicted by the classical DLVO theory, which considers contributions from the van der Waals-dispersion and double-layer forces to the disjoining pressure of the film. The discrepancy may be attributed to the presence of hydrophobic force, the magnitude of which has been estimated using the Reynolds lubrication approximation. It has been found that the attractive hydrophobic force was substantially larger than the attractive van der Waals force, which may explain the faster film thinning kinetics. With a given non-ionic surfactant, the hydrophobic force decreased with increasing surfactant concentration, which explained the slower kinetics observed at higher concentrations and hence the increased foam stability. At concentrations where the hydrophobic force became comparable to or smaller than the van der Waals force, the foam films were stabilized by the increased elasticity of the foam films. The film elasticity of the surfactant solutions were measured using the oscillating drop analysis technique at different frequencies. The measurements were conducted in the presence of CnEOm surfactants with n=10-14 and m=4-8, and the results were analyzed using the Lucassen and van den Tempel model (1972). There was a reasonable fit between the experiment and the model predictions when using the values of the Gibbs elasticity calculated from the Wang and Yoon model (2006). From this exercise, it was possible to determine the diffusion coefficients (D) of the CnEOm surfactants. The D values obtained for CnEOm surfactants were in the range of 2.5x10-10 to 6x10-9 m2s-1, which are in general agreement with those reported in the literature for other surfactants. The diffusion coefficient decreased with increasing alkyl chain length (n) and increased with increasing chain length (m) of the EO group. These findings are in agreement with the results of the dynamic surface tension measurements conducted in the present work. The TFPB studies were also conducted on the foam films stabilized in the presence of a mixture of C12EO8 and sodium dodecylsulfate (SDS) at different ratios. The results showed that the hydrophobic force increased with increasing C12EO8 to SDS ratio. Thus, the former was more effective than the latter in decreasing the hydrophobic force and hence stabilizing foam films. The C12EO8 was more efficient than SDS in increasing the elasticity of the single foam films and stabilizing foams. The TFPB studies were also conducted in the presence of n-octadecyltimethyl chloride (C18TACl) and polymers, i.e., polyvinylpyrrolidone (PVP) and polystyrene sulfonate (PSS). The effect of polymer on the film elasticity was strongest in the presence of PSS, which can be attributed to the charge-charge interaction. Nano-sized silica and poly methyl methacrylate (PMMA) particles were used as solid surfactants to stabilize foams. It was found that the foam stability was maximum at contact angles just below 90o. The TFPB studies conducted with silica nano-particles showed that the kinetics of foam films became slower as the contact angle was increased from 30o to 77 o , indicating that foam films becomes more stable with more hydrophobic particles. The extra-ordinary stability observed with the hydrophobic silica nano-particles may be attributed to the possibility that the particles adsorbed on bubble surfaces retard the drainage rate and prevent the films to reach the critical rupture thickness (Hc). Confocal microscope and SEM images showed that hydrophobized nano-particles adsorbed on the surfaces of air bubbles, and that some of the nano-particles form aggregates depending on the particle size and hydrophobicity. The dynamic surface tension measurements conducted with PMMA and silica nano-particles showed that the latter has higher diffusion rates than the former, which may be due to the differences in particle size and hydrophobicity. / Ph. D.

In addition to ventilation practices, the application of water via sprays is the most economical and popular means of combating respirable dust in an underground coal mine. Due to a noticeable increase in black lung among coal miners and new dust regulations, surfactants or wetting agents have been used to aid in dust suppression. The surfactant facilitates the wetting process by lowering the surface tension and allowing the hydrophobic coal dust to come into contact with the water. One of the most straightforward and effective benchtop tests is a simple wetting test. Although there are variations of this type of test, principle and technique remain the same. A known amount of dust was placed on the surface of a solution and the time it takes for all the dust to fall through the interface would be the wetting rate. This investigation examined the specific density of the bulk dust and concentration of a surfactant in solution and their effects on the wetting rate. It was found that both factors were significant in determining the wetting rate. It was seen that the surfactant had a more significant effect on the dust which consisted mostly of coal particle when compared to a dust with a higher non-coal mineral content. Additionally, full-scale tests were conducted to determine the effect of the surfactant at a constant concentration. During the field implementation, the surfactant was pumped through the mines spray water to the cutter heads of the continuous miner. A large number of uncontrollable variables present during the implementation, made determining the effects difficult, and the resulting impact from the surfactant inconclusive. Further long-term testing would be needed while accounting for all of the identified variables. Significantly higher concentration was however found when using the continuous personal dust monitor as opposed to the older personal dust samples when left in the same environment. Additionally, a very significant drop in dust concentrations was observed when the miner operators were allowed to activate the scrubbers. / Master of Science

Thesis advisor: Mary F. Roberts / Thesis advisor: Eranthie Weerapana / Peripheral proteins from mammals often exhibit multi-domain structures and require metal ions such as calcium as co-factors. This dissertation investigates two types of such proteins -- pulmonary collectins (surfactant proteins A and D) and phosphatidylinositol-specific phospholipase C (PLC) delta1 -- and their interactions with model membranes. One approach to work around the complexity brought upon by such multi-domain protein structure is to use a truncated construct or an isolated single domain. For pulmonary collectins, homotrimers consisting of the neck domain and the carbohydrate recognition domain were used in a novel NMR assay for better understanding of their lipid-specific interactions with the membranes. For PLC delta1, we were particularly interested in the role of the EF-hand domain. The isolated EF-hand domain of PLC delta1 was first used to characterize its interactions with membranes and identify key residues responsible for such interactions. These key residues in the N terminal lobe of the EF-hand domain, either cationic or hydrophobic, were then found to affect the hydrolysis activity of the full-length enzyme. A common role for this region of the PLC in facilitating proper membrane association was thus proposed. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Viscoelastic surfactant have found numerous application in the oil fields as fracturing and matrix acidizing fluid additives in the recent years. They have the ability to form long worm-like micelles with the increase in pH and calcium concentration, which results in increasing the viscosity and elasticity of partially spent acids. On one hand, concentration of surfactant in the fluids has profound effects on their performance downhole. Additionally, there is continuous debate in the industry on whether the gel generated by these surfactants causes formation damage, especially in dry gas wells. Therefore, being able to analyze the concentration of these surfactants in both live and spent acids is of great importance for production engineers who apply surfactant-based fluids in the oil fields. In the present work, a two-phase titration method was optimized for quantitative analysis of a carboxybetaine viscoelastic surfactant, and surfactant retention in calcite cores was quantitatively determined by two phase titration method and the benefits of using mutual solvents to break the surfactant gel formed inside the cores was assessed. On the other hand, high temperatures and low pH are usually involved in surfactant applications. Surfactants are subjected to hydrolysis under such conditions due to the existence of a peptide bond (-CO-NH-) in their molecules, leading to alteration in the rheological properties of the acid. The impact of hydrolysis at high temperatures on the apparent viscosity of carboxybetaine viscoelastic surfactant-based acids was evaluated in the present study, and the mechanism of viscosity changes was determine by molecular dynamics (MD) simulations. Our results indicate that, first, significant amount of surfactant has been retained in the carbonate matrix after acidizing treatment and there is a need to use internal breakers when surfactant-based acids are used in dry gas wells or water injectors. Second, hydrolysis at high temperatures has great impact on surfactant-acid rheological properties. Short time viscosity build-up and effective gel break-down can be achieved if surfactant-acid treatments are carefully designed; otherwise, unexpected viscosity reduction and phase separation may occur, which will affect the outcome of acid treatments.

Cette thèse s’inscrit dans le cadre de synthèses de matériaux innovants contenant des entités cationiques que sont le guanidinium et l’ammonium. Ces entités cationiques confèrent des propriétés intéressantes et fonctionnelles pour chacun des systèmes ioniques suivants : tensio-actifs, liquides ioniques et ionosilices. A cet effet, nous avons procédé à l’étude de deux familles de composés : les sels de guanidiniums et les ionosilices. Pour les sels de guanidiniums, nous avons étudié la formation et les propriétés d’auto-assemblage de tensio-actifs en utilisant différentes techniques de mesures (conductivité, tension de surface et calorimétrie). Ce remarquable synthon moléculaire qu’est le guanidinium a été aussi mis en avant comme liquide ionique pour l’extraction du méthyl orange, du diclofenac et du chromate. Quant aux ionosilices, bien qu’ils présentent aussi des propriétés intéressantes pour l’extraction ionique et l’adsorption de principes actifs, leur mise en forme reste cependant un paramètre clef pour cibler leur application. En effet, la mise en forme des ionosilices en nanoparticules permet l’extension des applications dans le domaine de la nanomedecine. Ainsi, durant cette thèse, des nanoparticules avec des sous-structures ioniques ammoniums sont synthétisées pour la première fois et utilisées comme nano-vecteur pour le relarguage d’un anti-inflammatoire (diclofenac). Par ailleurs, dans le but d’une extraction ionique en flux continu, des matériaux contenant des fonctions ioniques sous forme de monolithe ont été synthétisés à partir de précurseur ammonium par voie sol gel. Ainsi cette thèse nous a permis de trouver les éléments théoriques, illustratifs et expérimentaux des différentes facettes de la formation de matières à base d’unités cationiques aux propriétés remarquables que sont les sels de guanidiniums et les sels d’ammoniums. / This dissertation deals with innovative synthetic materials bearing cationic entities that are guanidinium and ammonium. These cationic entities give interesting and functional properties for each ionic system studied: surfactant, ionic liquid and ionosilica. For this purpose, we investigated two families groups composed of: guanidiniums salts and ionosilica. Regarding guanidiniums salts, we studied the formation and self-assembly behavior of guanidinium surfactants using different measurement techniques (conductivity, surface tension and calorimetry). This remarkable molecular synthon that represents guanidinium was also highlighted as an ionic liquid for the extraction of methyl orange, diclofenac and chromate. As for ionosilicas, although they also have advantageous properties for ion extraction and adsorption of the active ingredients, however their shaping remains a key parameter for targeting their application. In fact, the design of ionosilica material as nanoparticle allows applications extension in the field of nanomedicine. So during this thesis, nanoparticles containing ammonium substructures were synthesized for the first time and used as a nano-vector to deliver an anti-inflammatory drug (diclofenac). Furthermore, with the aim of ionic extraction in continuous flow, materials containing ionic functions as monolith were synthesized from ammonium precursor via sol gel route. This thesis allowed us to find the theoretical, experimental and illustrative elements of the different aspects of materials formation based on cationic entities with remarkable properties that are guanidiniums and ammonium salts.

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Orientador: David Mendez Soares / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-15T00:08:17Z (GMT). No. of bitstreams: 1 Gomes_WyllersonEvaristo1983-_M.pdf: 20027750 bytes, checksum: ac9756c2723f3eb80a562d792355af61 (MD5) Previous issue date: 2010 / Resumo: As propriedades dinâmicas e estruturais de filmes de surfatantes adsorvidos em superfícies são de interesse fundamental e aplicado. Investigamos a formação de estruturas auto-organizadas de surfatantes sobre superfícies de substrato sólido de ouro. Estudamos sua dinâmica de formação e estabilidade. As estruturas foram feitas em ambiente aquoso, sob condições físico-químicas controladas. Tais estruturas são potenciais candidatas a modelos in vitro de membrana biológica (sistema biomimético) / Abstract: The structural and dynamical properties of surfactant films are both of fundamental and applied interest. To understand the formation mechanism of these structures we have studied the formation of surfactant self-assembled aggregates on gold surfaces. Their dynamic and stability were investigated. All experiments were performed in aqueous media, under specific physical and chemical conditions. These structures are potential candidates of in vitro models for biological membranes (bio-mimetic systems) / Mestrado / Físico-Química / Mestre em Física

Doctorat en sciences médicales / info:eu-repo/semantics/nonPublished

Foam fractionation is an economical and environmentally friendly separation method for surface active material using a rising column of foam. The system of foam fractionation column with reflux is selected since such a system can improve the enrichment of the product collected from the top of the column. Due to the reflux, it is assumed that there is more surface active material (surfactant and/or protein) in the Plateau border than that in the foam lamella, so that the Plateau border acts as a surfactant/protein reservoir. The aim of this thesis is to investigate the adsorption and transport of surface active material such as surfactant and/or protein onto the surface of a lamella in a foam fractionation column with reflux using mathematical simulation. There are two steps involved in adsorption of surface active material onto a bubble surface within foam, which are diffusion from the bulk solution into the subsurface, a layer next to the interface, followed by adsorption of that material from the subsurface onto the interface. The diffusion follows the Fick's second law, while the adsorption may follow the Henry, Langmuir or Frumkin isotherms, depending on the properties of the surface active material. The adsorption of mixed protein-surfactant follows the Frumkin isotherm. When there is a competition between protein and surfactant, the protein arrives onto the interface at a later time due to a slower diffusion rate and it displaces the surfactant molecules already on the surface since protein has a higher affinity for that surface than surfactant. The surfactant transport from a Plateau border onto a foam lamella is determined by the interaction of forces applied on the lamella surface, such as film drainage, due to the pressure gradient between the lamella and the Plateau border, the Marangoni effect, due to the gradient of surface tension, and surface viscosity, as a reaction to surface motion. In this thesis, there are two different models of film drainage. One approach uses assumption of a film with a mobile interface and the other model assumes a film with a rigid interface. In the absence of surface viscosity, the Marangoni effect dominates the film drainage resulting in accumulation of surfactant on the surface of the foam lamella in the case of a lamella with a rigid interface. In the case of a film with a mobile interface, the film drainage dominates the Marangoni effect and surfactant is washed away from the surface of the lamella. When the drainage is very fast, such as that which is achieved by a film with a mobile interface, the film could be predicted to attain the thickness of a common black film, well within the residence time in a foam fractionation column, at which point the film stops draining and surfactant starts to accumulate on the lamella surface. The desirable condition in operation of a foam fractionation column however is when the Marangoni effect dominates the film drainage and surfactant accumulates on the surface of a foam lamella such as the one achieved by a film with a rigid interface. In the presence of surface viscosity and the absence of film drainage, the surface viscous forces oppose the Marangoni effect and reduce the amount of surfactant transport onto the foam lamella. A larger surface viscosity results in less surfactant transport onto the foam lamella. In addition, the characteristic time scale required for surfactant transport is shorter with a shorter film length.