Dissertations / Theses on the topic 'Surfactant aggregate'

Les particules fines émises par l'activité humaine sont la cause de diverses pathologies pulmonaires et cardiaques. Les particules de taille inférieure à 100 nm, appelées nanoparticules, sont particulièrement nocives car une fois inhalées, elles peuvent atteindre les alvéoles pulmonaires, lieux des échanges gazeux. Dans les alvéoles, les nanoparticules entrent d'abord en contact avec le surfactant pulmonaire. Ce fluide biologique tapisse les cellules épithéliales des alvéoles sur une épaisseur de quelques centaines de nanomètres et est composé de phospholipides et de protéines, les phospholipides étant assemblés sous forme de vésicules et corps multi-lamellaires. Dans ce travail, nous avons sélectionné des nanoparticules modèles de nature différente connues pour leur toxicité cellulaire (latex, oxydes métalliques, silice). Leur interaction avec un fluide pulmonaire mimétique administré aux prématurés (Curosurf®) a été étudiée en détail par microscopie optique et électronique, et par diffusion de la lumière. Nous avons mis en évidence que cette interaction est non spécifique et d'origine électrostatique. La diversité des structures hybrides obtenues entre particules et vésicules témoigne cependant de la complexité de cette interaction. En contrôlant cette interaction, nous avons formulé des particules couvertes d’une bicouche supportée de Curosurf® qui possèdent des propriétés remarquables de stabilité et de furtivité en milieu biologique.Dans une seconde partie, nous avons étudié le rôle du surfactant pulmonaire sur l’interaction entre particules et cellules épithéliales alvéolaires (A459). A l'aide d'expériences de biologie cellulaire réalisées in vitro, nous avons observé que la présence de surfactant diminue de manière significative le nombre de particules internalisées par les cellules. Dans le même temps, nous avons constaté une augmentation importante de la viabilité cellulaire. Une conclusion majeure de notre travail concerne la mise en évidence du rôle protecteur joué par le surfactant pulmonaire dans les mécanismes d'interaction des nanoparticules avec l'épithélium alvéolaire<br>Particulate matter emitted by human activity are the cause of various pulmonary and cardiac diseases. After inhalation, nanoparticles (ie particles smaller than 100 nm) can reach the pulmonary alveoli, where the gas exchanges take place. In the alveoli, the nanoparticles first encounter the pulmonary surfactant which is the fluid that lines the epithelial cells. Of a few hundreds of nanometers in thickness, the pulmonary fluid is composed of phospholipids and proteins, the phospholipids being assembled in multilamellar vesicles. In this work, we considered model nanoparticles of different nature (latex, metal oxides, silica). Their interaction with a mimetic pulmonary fluid administered to premature infants (Curosurf®) was studied by light scattering and by optical and electron microscopy. We have shown that the interaction is non-specific and mainly of electrostatic origin. The wide variety of hybrid structures found in this work attests however of the complexity of the phospholipid/particle interaction. In addition, we succeeded in formulating particles covered with a Curosurf® supported bilayer. These particles exhibit remarkable stability and stealthiness in biological environment. In a second part, we studied the role of the pulmonary surfactant on the interactions between nanoparticles and alveolar epithelial cells (A459). With cellular biology assays, we observed that the number of internalized particles decreases dramatically in presence of surfactant. At the same time, we found a significant increase in the A459 cell viability. Our study shows the importance of the pulmonary surfactant in protecting the alveolar epithelium in case of nanoparticle exposure

<p>The first part of this thesis is concerned with thestructure-property relationships in nonionic surfactantsystems. The main aim was to investigate how the surfactantstructure influences the adsorption at interfaces andinteractions between surfactant coated interfaces.Particularly, the effect of the structure of the surfactantheadgroups was investigated. These were sugar-based headgroupwith varying size and flexibility and poly(ethylene oxide)based headgroups with or without an additional amide or estergroup. The hydrophobic part of the surfactant consisted mostlyof straight alkyl chains, except for one type of poly(ethyleneoxide) based surfactant with a dehydroabietic hydrophobe.</p><p>The main technique that was used is the surface forcetechnique, with which the forces acting between two adsorbedsurfactant layers on hydrophilic or hydrophobic surfaces can bemeasured. These forces are important for e.g. the stability ofdispersions. The hydrophilic surfaces employed were glass andmica, whereas the hydrophobic surfaces were silanized glass andhydrophobized mica. The adsorption behavior on hydrophilicsurfaces is highly dependent on the type of headgroup andsurface, whereas similar results were obtained on the two typesof hydrophobic surfaces. To better understand how the surfaceforces are affected by the surfactant structure, measurementsof adsorbed amount and theoretical mean-field latticecalculations were carried out. The results show that the sugarsurfactant layers and poly(ethylene oxide) surfactant layersgive rise to very different surface forces, but that the forcesare more similar within each group. The structure-propertyrelationships for many other physical properties have beenstudied as well. These include equilibrium and dynamicadsorption at the liquid-vapor interface, micelle size, micelledynamics, and wetting.</p><p>The second part in this thesis is about the aggregationbetween cationic polyelectrolytes and an anionic surfactant.The surface force technique was used to study the adsorption ofa low charged cationic polyelectrolyte on mica, and theaggregation between the adsorbed polyelectrolyte with theanionic surfactant. The aggregation in bulk was studied withturbidimetry, small angle neutron scattering (SANS), and smallangle x-ray scattering (SAXS). An internal hexagonal aggregatestructure was found for some of the bulk aggregates.</p><p><b>Keywords:</b>nonionic surfactant, sugar surfactant,poly(ethylene oxide), amide, ester, polyelectrolyte, SDS,hydrophobic surface, glass surface, mica, adsorption,aggregation, micelle size, surface forces, wetting, dynamicsurface tension, NMR, TRFQ, SANS, SAXS, mean-field latticecalculations.</p>

Polyelectrolyte-surfactant aggregates (PES) have diverse sets of properties, which could be controlled by a wide range of parameters, both within the aggregates themselves and the surrounding environment. The large portfolio of applications amplifies the need to understand them. A particular system of polyelectrolyte-surfactant aggregate, polycetyltrimethyl vinylbenzoate, denoted pC16TVB, which self-assembles in aqueous solution, is the main focus of the thesis. Its structure is the product of the balance between surfactant head groups – polyelectrolyte charge groups electrostatic interactions and surfactant tails – polyelectrolyte backbone hydrophobic interactions. At neutral solution pH, the structure is one of a core-shell cylinder, with the shell consisting of surfactant heads. The surfactant tails point toward the core center, while the polyelectrolyte also resides in the core, but remains close to the core-shell interface for charge neutralization. As the pH drops to 1.0, the balance is disrupted with the hydrophobic interaction being increasingly dominant while electrostatic interaction is reduced, and the structure transforms into a more commonly seen string-of-pearl, in which the polymer chain connects a series of spherical surfactant micelles. The solution properties are impacted accordingly, becoming viscoelastic while solubilizing 10 times more hydrophobic molecules. Treating the pC16TVB aggregate as a whole, its adsorption onto oxide nanoparticles surfaces has been analyzed, extended from a previous flat surface adsorption work. Aided by hydrophobic dyes as molecular trackers, the adsorbed thickness has been proven to be a function of the surface curvature, with less curve surface adsorbs more material. The dye loading remains intact after the adsorption, enabling the use of the aggregate as a delivery vehicle for hydrophobic materials in aqueous solution. The resulting adsorption of pC16TVB aggregate onto SiO2 surfaces has a core-shell sphere structure. Unlike for flat surfaces, in which the adsorption mechanism has been shown previously to consist of two main steps, with some dissociated surfactant molecules adsorbing head first via electrostatic attraction with the surface to create hydrophobic anchor points for further aggregate adsorption, the high bending energy cost and the low aggregate concentration (relative to the total sphere surface area) suspend the adsorption after the initial surfactant adsorption step

O uso e estudo de materiais híbridos para desenvolver novos materiais com qualidades superiores para aplicações em fotônica, sensores e áreas afins é um desafio para o químico. Neste contexto deve-se especular sobre as propriedades de associação de materiais orgânicos e inorgânicos para alcançar novas e melhores propriedades. Neste estudo, os óxidos metálicos (óxidos de cério em particular), uma classe especial entre nanopartículas inorgânicas, foram selecionados para explorar as suas aplicações com uma classe, também especial de compostos orgânicos, sendo no nosso estudo as Naftaleno Diimidas. Óxido de cério é um semicondutor, com uma &#8220;bandgap&#8221; larga, conhecido por sua capacidade catalítica e por sua simples manipulação para preparar filmes finos e nanopartículas. Derivados de Naftaleno Diimidas são conhecidos por sua superior atividade eletroquímica comparáveis aos dos Paraquat (metilviologênio), mas com amplitude maior de aplicações fotoquímicas. Foram sintetizadas Naftaleno Diimidas carregados positivamente e negativamente com propriedades surfactantes. Após a caracterização detalhada das Naftaleno Diimidas, incluindo auto-associação e interação com moléculas de surfactantes, a interação com nanopartículas de óxido de cério foram determinadas. As Naftaleno Diimidas interagiram de forma especial com nanopartículas de óxido de cério conferindo ausência de atividade hidrolítica e um comportamento fotocrômico singular. Propõe-se que o corante orgânico se adsorve nas ranhuras das nanopartículas e, além disso forma dímeros estáveis que têm importância para as novas fotoatividades observadas.<br>The use and study of hybrid materials is a challenge for the chemist to develop materials having new and superior qualities for applications in photonics, sensors and related areas. In this context one has to speculate on the properties of the organic and inorganic partners to achieve better and new properties. In this study the metal oxides (in particular Cerium Oxides), a special class among inorganic nanoparticles were selected to exploit their applications with an also special class of organic compounds the Naphthalene Diimides. Cerium Oxide is a wide bandgap semiconductor well known for its catalytic capabilities and for its simple manipulation to prepare thin films and nanoparticles. Naphthalene Diimides derivatives are known for their superior lectrochemical activities comparable to those of Paraquat (Methyl Viologen) but with larger amplitude of photochemical applications. Positively and negatively charged, surfactant like, Naphthalene Diimides, were synthesized. After detailed characterization of the Naphthalene Diimides including selfassociation and interaction with surfactant molecules, the interaction with Cerium Oxide nanoparticles was determined. Naphthalene Diimides interacted in a special manner with Cerium Oxide nanoparticles rendering hydrolytic inertness and novel photochromic behavior. The organic dye is proposed to adsorb in the crevices of the particles and furthermore forming stable dimers that accounts for the new photoactivities observed

Dilute metallic ion treatment (< 10 mg/L) remains a challenge in water purification and resource recovery. A novel and inexpensive treatment process that employs polymer-surfactant aggregates (PSAs) has been developed and applied to remove and recover dilute metallic ions, such as Cr3+, Rh3+, Cd2+, Fe(CN)6 3- and CrO42-, from industrial process and effluent. At the heart of this process is a material that comprises a colloidal structure of polymers and surfactants, named a polymer-surfactant aggregate (PSA), that trap metallic ions. The ion loaded PSAs then coalesce and settle out. The flocs are then treated separately by acid-base wash to recover the ions in a concentrated salt and regenerate the polymer and surfactant. The regenerated polymer and surfactant can then be recycled without a deterioration of removal ability in the next cycle. This process is simple, uses low energy, and generates little material loss or discharge. The thesis is divided into three main parts: fundamentals, cation treatment and anion treatment. First, the mechanism of formation of PSAs and their interactions with metallic ions are investigated using surface tension and electrical conductivity measurements. Both measurements reveal that the PSA is formed by surfactant monomers binding to the oppositely charged polymer chains and forming micelle-like aggregates via hydrophobic and electrostatic forces. These aggregates, like micelles, can bind to the oppositely charged metallic ions, but the surfactant concentration required is a few orders of magnitude lower than that required for micelle formation. The resulting nano-size PSA has a large surface area to volume ratio, and can effectively treat dilute aqueous streams. Each PSA consists of positive and negative charges. Within a near charge neutralisation range, they can quickly self-flocculate to simultaneously remove metallic ions and settle the flocs out of aqueous solutions. Correlating the removal efficiency of ions with surface tension and electrical conductivity measurements, the results suggest that the PSA is indeed responsible for removing the ions from the streams. Based on the fundamentals, a PSA process consisting of three stages (removal, recovery and recycle) is developed to treat metal cations in dilute streams. At the removal stage, polymer and surfactant (i.e. removal agent) are used to form PSAs and trap 99% of 0.1 mM metal ions into flocs. At the recovery stage, a small amount of acid solution is added to leach out 95% of the trapped metal ions into a concentrated salt, and then using a base solution to completely dissolve and regenerate the removal agent. After that, the removal agent are recycled in the next cycle without the need for any make-up, and little deterioration of removal ability is found. The same three-stage process is also applied to recover dilute metallic anions. As the targeted ions are negatively charged, the charge of polymer and surfactant used and the order of acid-base wash are reversed as compared with the cation treatment process. The PSA process is robust under different conditions, e.g. pH, temperature, salinity and organic contaminants. Such a sustainable process thus has potential applications for the efficient removal and recovery of dilute metallic ions during process effluent water treatment.

This work is focused on the study of interaction between hyaluronan and high-biocompatible amphiphilic molecules. Using fluorescent probe method, screening of the interaction of cationic lipid 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), mixture of this cationic lipid with zwitterionic lipid, 1,2-dipalmitoyl-sn-glycero-3-phosphochloline (DPPC), with hyaluronan, both native and hydrophobically modified was carried out. Results showed the self-aggregation of DPPC and DPTAP independently on lipids ratio in the mixture and the interaction of DPTAP and DPPC/DPTAP aggregates with hyaluronan at specific ratio of DPTAP and hyaluronan concentration. Physical properties of formed membranes and the influence of cholesterol were also investigated at different DPPC and DPTAP concentration ratio. Last but not least, the non-ionic surfactant-DPPC systems were studied, namely, the size of the formed aggregates, the thermodynamics of solubilisation and the interaction with native hyaluronan.

L’idée directrice de ce travail de thèse était d’introduire au sein de mésophases lipidiques des molécules de β-cyclodextrine (βCD) amphiphiles obtenue par bio-estérification afin d’obtenir des nano-assemblages plurimoléculaires et multi-compartimentés combinant trois fonctions essentielles pour le transport ou la vectorisation de molécules thérapeutiques : (i) la capacité d’incorporer une substance d’intérêt par formation de complexe d’inclusion avec la cyclodextrine ; (ii) être biocompatibles et aptes à passer facilement les barrières biologiques ; (iii) pouvoir co-incorporer une seconde substance d’intérêt, hydrophile ou hydrophobe, dont l’action biologique soit différente de celle assurée par la première substance. L’ensemble des travaux ont porté sur le dérivé βCD-C10 polysubstitué en face secondaire par des chaînes hydrocarbonées en C10 avec un degré moyen de substitution de 7,5. L’association de ce dérivé avec trois catégories de lipides a été envisagée : des tensioactifs micellaires non-ioniques (Brij 98, Polysorbate 80, n-dodécyl-β-D-maltoside), un lipide lyotrope non lamellaire formant des mésophases de type cubique bicontinue (monooléine), un phospholipide s’auto-organisant en bicouches propices à l’obtention de vésicules (dimyristoyl phosphatidylcholine). Selon une démarche principalement physico-chimique, différentes techniques ont été mises en œuvre pour caractériser les systèmes mixtes lipide/βCD-C10 aux échelles moléculaire et supramoléculaire : diffusion-diffraction des rayons X, calorimétrie différentielle, spectrophotométrie d’absorption UV-visible, spectroscopie de fluorescence, diffusion de la lumière statique (turbidimétrie) ou quasi-élastique, microscopie optique et microscopie électronique par cryo-transmission. L’ensemble des résultats démontrent que le dérivé βCD-C10 forme spontanément ou selon un protocole très simple, des assemblages plurimoléculaires mixtes avec les trois catégories de lipides, assemblages dont la topologie dépend de la structure chimique du lipide et du taux de cyclodextrine amphiphile incorporé (tubules, vésicules uni- ou oligolamellaires, cubosomes). Ces assemblages sont stables et capables d’incorporer une substance hôte hydrophobe, notamment les vésicules mixtes tensioactif non-ionique/ βCD-C10 et les cubosomes mixtes monooléine/P80/ βCD-C10<br>The key idea of this Ph.D. thesis is to introduce amphiphilic β-cyclodextrin molecules (βCD), obtained by bio-transesterification, within lipid mesophases in order to obtain multi-compartment plurimolecular nano-assemblies, which combine three essential functions for transport or delivery of therapeutic molecules: (i) capacity to incorporate a substance of interest through formation of inclusion complexes with the modified cyclodextrin; (i) biocompatibility and ability to easily pass the biological barriers; and (iii) possibility for co-encapsulation of a second substance of interest, a hydrophilic or a hydrophobic one, whose biological action is different from that provided by the first substance. The performed Ph. D. work focused on the β-cyclodextrin derivative βCD-C10 with an average degree of substitution of 7.5 of the secondary face of the macrocycle by hydrocarbon chains C10. The association of this derivative with three classes of amphiphiles was studied: (i) nonionic micellar surfactants (Brij 98, Polysorbate 80, n-dodecyl β-D-maltoside), (ii) a lyotropic nonlamellar lipid forming bicontinuous cubic mesophases (monoolein), and (iii) a phospholipid (dimyristoyl phosphatidylcholine), which self-ssembles into bilayer membranes permitting the production of vesicles.The employed physical-chemical approach involved different techniques for characterization of the mixed βCD-C10/lipid systems at molecular and supramolecular levels: cryo-transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, UV-visible absorption spectroscopy, fluorescence spectroscopy, turbidimetry, and quasi-elastic light scattering.The obtained results indicated that the βCD-C10 derivative forms spontaneously (or via a very simple preparation protocol) plurimolecular mixed nano-assemblies with the three types of lipids. The topologies of the resulting nano-assemblies essentially depend on the chemical structures of the lipids and the degree of incorporation of the amphiphilic cyclodextrin (tubules, unilamellar or oligolamellar vesicles, and cubosomes). These assemblies, namely the mixed vesicles of nonionic surfactant/βCD-C10 and the cubosomes of mixed monoolein/P80/βCD-C10 compositions, are stable and capable of incorporation of hydrophobic guest substances

碩士<br>國立臺灣大學<br>化學研究所<br>96<br>The pH-sensitive anionic surfactant has been synthesized and its aggregate behaviors in the aqueous solution have been studied at different pH value. At higher pH value, the anionic surfactant will be fully de-protonated as a divalent molecule and generate higher curve aggregate, micelle. At lower pH value, the anionic surfactant will gradually be protonated and generate lower curve aggregate, vesicle or acid soap precipitate. The driving force that dominates their packing behaviors is hydrogen bonding generated from adjacent partial protonated surfactants. The cationic fluorescent surfactant has been synthesized and its aggregate behaviors in the aqueous solution have been studied by fluorescence measurements owing to its intrinsic fluorescent probe. When surfactant concentrations increase above the critical micelle concentration (CMC), the emission wavelength would red shift because of excimer formation. Furthermore, the emission wavelength will not only shift to shorter wavelength but also increase quantum efficiency in less polar medium owing to the de-formation of aggregate. Similarly, the addition of anionic surfactant sodium dodecyl sulfate into the surfactant solution at different ratio also gives rise to the blue-shift wavelength and the increase of quantum efficiency.

Electrospun nanofibers have improved physicochemical properties compared to macroscalar fibers and are therefore increasingly investigated for use in novel food packaging systems. The objectives of this study were to electrospin nanofibers and to evaluate the effect and feasibility of surfactants and surfactant aggregates to modulate properties and functionalities of electrospun nanofibers. Nanofibers were fabricated by electrospinning a mixture of cationic chitosan and noncharged poly(ethylene oxide) (PEO) in aqueous acetic acid. To improve spinnability and nanofiber morphologies, surfactants were added to biopolymer/polymer solutions and their influence was investigated. Solution properties were evaluated by rheological, surface tension, and conductivity measurements. Fibers were characterized by scanning and transmission electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Addition of PEO and surfactants induced spinnability producing larger fibers with diameters ranging from 40 to 240 nm, while pure chitosan did not form fibers and was instead deposited as beads. Compositional analysis suggested that nanofibers consisted of all solution constituents with chitosan concentrations being significantly lower in fibers than in solution, indicating that surfactants may have decreased polymer-polymer interactions responsible for entanglement. Poly(vinyl alcohol) nanofibers were used as novel delivery system for eugenol carrying Surfynol®465 micelles (microemulsion). Solution properties were not significantly altered after addition of microemulsion regardless of surfactant and/or eugenol concentration. Transmission electron imaging revealed a homogeneous distribution of microemulsion throughout the nanofibers. Release studies suggested a burst release mechanism of encapsulated eugenol microemulsion, potentially due to hydrophilicity of the polymeric carrier, while faster release was observed in samples with a higher eugenol loading ratio in the microemulsion. Antimicrobial activity of produced nanofibers carrying phytophenol microemulsions was evaluated against two strains of Salmonella Typhimurium and Listeria monocytogenes. Overall, the functionalized nanofibers had higher antimicrobial efficacies against Gram-negative than Gram-positive bacterial strains and were also more effective than pure eugenol microemulsion added at respective concentrations to the test system possibly due to a faster exhaustion and loss of antimicrobial activity in free microemulsions. Results of this study suggest that composite solutions of biopolymers, synthetic polymers, and micellar surfactant solutions can be successfully electrospun potentially offering a new means to functionalize biopolymeric nanofibers.