Sistema microemulsionado: caracteriza����o e aplica����o na ind��stria de petr��leo

Alkyl polyethoxylates are surfactants widely used in vastly different fields, from oil exploitation to pharmaceutical applications. One of the most interesting characteristics of these surfactants is their ability to form micellar systems with specific geometry, the so-called wormlike micelle. In this work, microemulsions with three distinct compositions (C/T = 40 %, 30 % and 25 %) was used with contain UNITOL / butanol / water / xylene, cosurfactant / surfactante (C/S) ratio equal to 0,5. The microemulsion was characterized by dynamic light scattering (DLS), capillary viscometry, torque rheometry and surface tensiometry experiments carried out with systems based on xylene, water, butanol (cosurfactant) and nonaethyleneglycolmonododecyl ether (surfactant), with fixed surfactant:cosurfactant:oil composition (with and without oil phase) and varying the overall concentration of the microemulsion. The results showed that a transition from wormlike micelles to nanodrops was characterized by maximum relative viscosity (depending on how relative viscosity was defined), which was connected to maximum effective diameter, determined by DLS. Surface tension suggested that adsorption at the air water interface had a Langmuir character and that the limiting value of the surfactant surface excess was independent of the presence of cosurfactant and xylene. The results of the solubilization of oil sludge and oil recovery with the microemulsion: C/S = 40%, 30% and 25% proved to be quite effective in solubilization of oil sludge, with the percentage of solubilization (%solubilization) as high as 92.37% and enhanced oil recovery rates up to 90.22% for the point with the highest concentration of active material (surfactant), that is, 40%.

Molecular Variations In Aromatic Cosolutes: Critical Role In The Rheology Of Cationic Wormlike Micelles.

Wormlike micelles formed by the addition to cetyltrimethylammonium bromide (CTAB) of a range of aromatic cosolutes with small molecular variations in their structure were systematically studied. Phenol and derivatives of benzoate and cinnamate were used, and the resulting mixtures were studied by oscillatory, steady-shear rheology, and the microstructure was probed by small-angle neutron scattering. The lengthening of the micelles and their entanglement result in remarkable viscoelastic properties, making rheology a useful tool to assess the effect of structural variations of the cosolutes on wormlike micelle formation. For a fixed concentration of CTAB and cosolute (200 mmol L(-1)), the relaxation time decreases in the following order: phenol > cinnamate> o-hydroxycinnamate > salicylate > o-methoxycinnamate > benzoate > o-methoxybenzoate. The variations in viscoelastic response are rationalized by using Mulliken population analysis to map out the electronic density of the cosolutes and quantify the barrier to rotation of specific groups on the aromatics. We find that the ability of the group attached to the aromatic ring to rotate is crucial in determining the packing of the cosolute at the micellar interface and thus critically impacts the micellar growth and, in turn, the rheological response. These results enable us for the first time to propose design rules for the self-assembly of the surfactants and cosolutes resulting in the formation of wormlike micelles with the cationic surfactant CTAB.

Efeitos estruturais e cin��ticos de micelas invertidas sobre uma amidase de pseudomonas aeruginosa

No presente trabalho foi executado o encapsulamento de c��lulas intactas, extracto celular e amidase purificada (E.C. 3.5.1.4) da estirpe L10 e AI3 de Pseudomonas aeruginosa num sistema de micelas invertidas composto pelo surfactante cati��nico brometo de tetradeciltrimetilam��nio (TTAB) em heptano/octanol 80/20 (v/v). O efeito do encapsulamento no sistema de micelas invertidas foi estudado avaliando a reac����o de transamida����o para s��ntese de ��cido acetohidrox��mico, catalisada pela amidase expressa por ambas as estirpes. No sistema de micelas invertidas fez-se variar conte��do de ��gua (w0) e foi estudado o efeito na actividade enzim��tica e no rendimento de s��ntese de acetohidroxamato. Os resultados demonstraram um aumento consider��vel de actividade espec��fica e do rendimento de s��ntese no sistema de micelas comparativamente ao meio convencional aquoso, sugerindo que a metodologia de encapsulamento do biocatalisador demonstrou potencialidades de utiliza����o na s��ntese de hidroxamatos, compostos de elevada import��ncia e aplicabilidade. Na varia����o do conte��do de ��gua no sistema micelar obteve-se uma curva em sino de actividade espec��fica e de rendimento, com um pico de actividade para w0 = 10, quer em c��lulas intactas, extracto celular e amidase purificada de ambas as estirpes. No caso da Pseudomonas aeruginosa L10 alcan��aram-se actividades espec��ficas de 8, 11 e 103 UI/mg de prote��na e rendimentos de 94, 99 e 40 % respectivamente para c��lulas intactas, extracto celular e amidase purificada. Quanto �� Pseudomonas aeruginosa AI3 obtiveram-se, respectivamente, actividades espec��ficas de 5, 9 e 163 UI/ mg de prote��na e rendimentos de 66, 66 e 28 % para c��lulas intactas, extracto celular e amidase purificada. A estabilidade de armazenamento do biocatalisador no sistema de micelas invertidas e em solu����o aquosa a 24��C foi avaliada. Este estudo revelou um aumento do t1/2 no sistema de micelas face ao armazenamento em solu����o aquosa convencional. No caso da Pseudomonas aeruginosa L10 os melhores resultados foram obtidos para a amidase purificada encapsulada revelando um t1/2 de 17 dias. Quanto ao extracto celular da Pseudomonas aeruginosa AI3 demonstrou um t1/2 de 26 dias quando encapsulado no sistema de micelas. O estudo das altera����es estruturais na amidase, de ambas as estirpes, devidas ao encapsulamento em micelas invertidas foi realizado recorrendo �� espectroscopia de FTIR. Esta an��lise permitiu verificar que a amidase AI3 n��o alterou significativamente a sua estrutura secund��ria em micelas invertidas para diferentes w0. No entanto, no encapsulamento a sua estrutura secund��ria sofreu altera����es face �� estrutura do enzima em solu����o aquosa. A amidase L10 exibe apenas altera����es estruturais face �� estrutura que exibe em solu����o aquosa quando confinada em micelas para w0 3,5 e 4.

Forma����o de micelas mistas entre o sal biliar colato de s��dio e o surfactante ani��nico dodecanoato de s��dio

Mixed-micelle formation between sodium chlolate (NaC) and the anionic surfactant sodium dodecanoate (SDoD) in Tris-HCl buffer solutions, pH 9.00, varying the molar fraction of the surfactants, was investigated by means of electrical conductivity and steady-state fluorescence of pyrene. The critical micelar concentration (cmc) was measured from the equivalent conductance versus the square root of the molar surfactant concentration plots and the regular solution theory (RST) was used to predict the mixing behavior. The I1/I3 pyrene ratio-surfactant concentration plots were used as an additional technique to follow the behavior and the changes in the micropolarity of the mixed micelles.

Control de la s��ntesis dirigida por micelas para la obtenci��n de nanoestructuras de ��xidos de manganeso con uso potencial en capacitores electroqu��micos

Tesis (Doctor en Ciencias con Orientaci��n en Qu��mica de los Materiales) UANL, 2010.

Wormlike micelle formation and flow alignment of a pluronic block copolymer in aqueous solution

The self-assembly into wormlike micelles of a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymer Pluronic P84 in aqueous salt solution (2 M NaCl) has been studied by rheology, small-angle X-ray and neutron scattering (SAXS/SANS), and light scattering. Measurements of the flow curves by controlled stress rheometry indicated phase separation under flow. SAXS on solutions subjected to capillary flow showed alignment of micelles at intermediate shear rates, although loss of alignment was observed for high shear rates. For dilute solutions, SAXS and static light scattering data on unaligned samples could be superposed over three decades in scattering vector, providing unique information on the wormlike micelle structure over several length scales. SANS data provided information on even shorter length scales, in particular, concerning "blob" scattering from the micelle corona. The data could be modeled based on a system of semiflexible self-avoiding cylinders with a circular cross-section, as described by the wormlike chain model with excluded volume interactions. The micelle structure was compared at two temperatures close to the cloud point (47 degrees C). The micellar radius was found not to vary with temperature in this region, although the contour length increased with increasing temperature, whereas the Kuhn length decreased. These variations result in an increase of the low-concentration radius of gyration with increasing temperature. This was consistent with dynamic light scattering results, and, applying theoretical results from the literature, this is in agreement with an increase in endcap energy due to changes in hydration of the poly(ethylene oxide) blocks as the temperature is increased.

Aplica����o da espectroscopia de absor����o de raios X no estudo do comportamento do ��on Cu2+ em micelas inversas

This work deals with the application of X-Ray Absorption Spectroscopy on the study of the behavior of Cu2+ ions in inverse micelles. The formation of copper nanoparticles in water-in-oil microemulsions in pseudo-ternary systems of cetyl trimethylammonium Bromide (CTAB) surfactant, butanol co-surfactant, heptane as oil phase and aqueous solutions of CuSO4.5H2O, and NaBH4. The microemulsions were prepared with a fixed percentage (60 %) of oil phase and a variable water to tensoative proportion. It was observed an increase on Cu2+ reduction by the sodium borohydride in microemulsions with 13 % of aqueous phase, independent of the reaction time. For the microemulsions in which the aqueous phase is composed only by the CuSO4 solution, it was observed that the color of the solution depends on the water to surfactant ratio. These changes in color were attributed to a competition for the hidratation water between the polar head of the tensoative and Cu2+ ions with the eventual substitution of oxygen by bromine atoms in the first coordination shell of Cu2+ ions

Efeito fotodin��mico da curcumina em micelas de cetrimida sobre cepas de candida suscept��veis e resistentes a fluconazol

P��s-gradua����o em Bioci��ncias e Biotecnologia Aplicadas �� Farm��cia - FCFAR

Transi����o ves��cula-micela em misturas de dispers��es de ves��culas com solu����es de micelas

P��s-gradua����o em Biof��sica Molecular - IBILCE

Efeito da desintegrina recombinante DisBa-01 incorporada em micelas ou livre em c��lulas portando ou n��o a integrina ��v��3

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Synthesis of wormlike nanoporous nickel oxide with nanocrystalline framework for electrochemical energy storage

In this work, nanoporous nickel oxide was synthesized using anionic surfactant assembly method. Structure characterizations show that this nickel oxide possesses partly-ordered mesoporous structure with nanocrystalline pore wall. The formation mechanism of wormlike nanoporous structure is ascribed to the quasi-reverse micelle system formed by ternary phases of SDS (sodium dodecyl sulfate)/urea/water. Cyclic voltammetry shows that these nickel oxide samples possess both good capacitive behavior due to its unique nanoporous structure and very high specific capacitance due to its high surface area with electrochemical activity.

Uma revis��o sobre o efeito Toms: o fen��meno onde macromol��culas atenuam a turbul��ncia em um l��quido

It is very well known that the addition of polymers to a liquid increases the shear viscosity of the solution. In other words, the polymer increases the dissipation of the flow energy. Contrarily, in turbulent flow, some particular macromolecules in very low concentration are able to produce large attenuation in the turbulence and thus, decreasing the dissipation of the energy. This article present a brief revision about macroscopic and molecular models used to explain this dynamic effect. Some of the experimental techniques used to quantify the attenuation of the turbulence and the main active substances are also discussed.

Reversible Photorheology in Solutions of Cetyltrimethylammonium Bromide, Salicylic Acid, and trans-2,4,4 '-Trihydroxychalcone

We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethylammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,4'-trihydroxychalcone (Ct). Different chemical species of Ct are associated with different colorations and propensities to reside within or outside CTAB micelles. A light-induced transfer between the intra- and intermicellar space is used to alter the mean length of wormlike micelles and hence the rheological properties of the fluid, studied in steady-state shear Bow and in dynamic rheological measurements. Light-induced changes of fluid rheology are reversible by a the relaxation process. at relaxation rates which depend on pH and which are consistent with photochromic reversion rates measured by UV-vis absorption spectroscopy. Parameterizing viscoelostic rheological states by their effective relaxation time tau(c) and corresponding response modulus G(c), we find the light and dark states of the system to fall onto a characteristic state curve defined by comparable experiments conducted without photosensitive components. These reference experiments were prepared with the same concentration of CTAB, but different concentrations of HSal or sodium salicylote (NaSal), and tested at different temperatures.

Estudo do comportamento reol��gico de sistemas complexos micelares

O surfactante Brometo de Cetiltrimetilam��nio (CTAB), quando dissolvido em ��gua, agrega-se espontaneamente em micelas, que crescem uniaxialmente ap��s introdu����o de aditivos, tornando-se elongadas e sucessivamente mais entrela��adas. Apresenta-se um estudo reol��gico para este surfactante, usando diferentes aditivos com o objectivo de produzir fluidos que exibem reologia manipul��vel, por influ��ncia da temperatura, concentra����o de aditivos e condi����es de ilumina����o (aus��ncia ou irradia����o com luz UV, no sistema foto-reol��gico). A caracteriza����o dos sistemas �� feita recorrendo a ensaios de fluxo em escoamento estacion��rio, de varrimento de temperatura, din��micos e de espectrofotometria. No sistema neutro (pH=7), os aditivos s��o os sais Salicilato de S��dio (NaSal) e Brometo de Pot��ssio (KBr), onde se demonstra que o NaSal promove mais eficazmente o crescimento micelar que o KBr. O sistema passa de ter um comportamento pr��ximo do Newtoniano a baixas concentra����es de aditivos para um comportamento n��o-Newtoniano quando a composi����o est�� acima da concentra����o cr��tica de sobreposi����o, exibindo fen��menos de reofluidifica����o e reoespessamento; adicionalmente, o tempo de relaxa����o aumenta. As altera����es reol��gicas que surgem com o aumento da temperatura devem-se �� diminui����o do comprimento micelar. O sistema ��cido (pH=2) obt��m-se adicionando ��cido Salic��lico(HSal) em substitui����o do NaSal. O seu comportamento reol��gico �� qualitativamente compar��vel ao sistema contendo NaSal, apesar dos valores de viscosidade serem no geral menores. Ao sistema ��cido adiciona-se o composto fotocr��mico trans-2,4,4,-Trihidroxichalcone (Chalcone), originando um sistema foto-reol��gico. Em solu����es micelares de CTAB a pH ��cido, o Chalcone exibe fotocromismo, mudan��a de cor revers��vel ap��s irradia����o no UV. Diferentes estados conformacionais associados com diferentes colora����es est��o tamb��m associados com diferentes afinidades de residir dentro ou fora das micelas, sugerindo que uma transfer��ncia de Chalcone, induzida por irradia����o, entre o espa��o intra e inter micelar pode ser usada para manipular o comprimento das micelas e consequentemente as propriedades reol��gicas intr��nsecas. As altera����es foto-reol��gicas s��o revers��veis por um processo de relaxa����o t��rmica, a taxas que dependem do pH.

Dispositivos moleculares com base em sistemas fotocr��micos

Disserta����o apresentada para obten����o do Grau de Doutor em Qu��mica,especialidade de Qu��mica-F��sica, pela Universidade Nova de Lisboa, Faculdade de Ci��ncias e Tecnologia