Dissertations / Theses on the topic 'Synergistic mixtures of surfactants'

An investigation was undertaken into the crystallisation process of the natural surfactants sodium laurate, myristate and palmitate. A multi-pass zone refiner was modified for purification of fatty acids, the starting materials in soap manufacture. It was found that purified lauric and myristic acid transform spontaneously in the solid state over a period of days from the C (=a) form to the A-super (=y) form, which was previously unknown. Low levels of impurities were found to inhibit this phase transformation. This was explained in terms of molecular rearrangement necessary for this transition. The nucleation behaviour from the isotropic micellar phase of single and mixed surfactant systems was studied using a specially developed turbidity probe. A two step nucleation and dissolution process was found to occur for some surfactant mixtures. Since this was not observed during static in-situ XRD experiments, it was postulated that during crystallisation above a certain degree of agitation segregation occurs of the two surfactants present in the mixture. Based on induction time measurements the size of the critical nucleus was estimated. The results indicated that the shorter the chainlength the more molecules are required to form a stable nucleus. The crystallisation process of single and mixed surfactant systems from the isotropic micellar phase, the hexagonal and the lamellar liquid crystalline phases was investigated by in-situ XRD using synchrotron radiation. A detailed transformation mechanism for the crystallisation process from the liquid crystalline phases was proposed based on epitaxial relations between all ordered phases of the following sequence: lamellar, tetragonal mesh, hexagonal mesh, (deformed hexagonal for surfactant mixtures with a chainlength difference of two CH2 groups), hexagonal, isotropic micellar, solid phase. Crystallisation of soap from ethanol-water mixtures revealed the ethanol to be incorporated into the micelles and to affect thresulting solid state structure above a certain ethanol content.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 249-264).
This thesis focuses on two research areas that are particularly relevant to the practical application of surfactant science: (1) the micellization of multicomponent surfactant mixtures, and (2) the micellization of pH-sensitive (or amphoteric) surfactants. Surfactant formulations of practical utility typically consist of many surfactant components. In many practical applications, pH-sensitive surfactants are added as a secondary surfactant because they enhance performance properties, including solubility, foaming, and mildness to the skin or to the eyes. In addition, pH-sensitive surfactants may be used eectively in novel applications where pH variations can be utilized to control self-assembly, including controlled drug release, targeted gene delivery, and the fabrication of nanoscale materials for optics, electronics, and sensors. First, a molecular-thermodynamic (MT) theory was developed to account for counterion binding to mixed micelles composed of ionic-nonionic and ionic-zwitterionic binary surfactant mixtures. The theory successfully predicted the degree of counterion binding ([beta]) of monovalent and multivalent ions to mixed micelles as a function of the micelle composition ([alpha]).
(cont.) The theory was also found to be consistent with the concept of critical counterion binding. An inection in the [beta vs. [alpha] curve was correlated to a micelle shape transition. Second, the MT theory was generalized to include pH eects in order to model the micellization of pH-sensitive surfactants. The theory was validated by comparing predictions of critical micelle concentrations (cmc's), micelle aggregation numbers, and micellar titration behavior to experimental data for alkyldimethylamine oxide surfactants, which are cationic in the protonated state (at low pH) and zwitterionic in the deprotonated state (at high pH). The MT theory qualitatively reproduced the minimum in the cmc and the maximum in the micelle aggregation number, which are both observed experimentally at intermediate pH values, resulting from the synergy between the two forms of the pH-sensitive surfactant in the micelle. This self-synergy, which was previously attributed by other researchers to the formation ofsurfactant-surfactant hydrogen bonds in the micelle, was rationalized instead in terms of electrostatic interactions operating between surfactants and bound counterions in the micelle. Very good quantitative agreement was obtained for the predicted cmc's in solutions containing no added salt.
(cont.) In particular, the experimentally observed maximum in the cmc, which originated from changes in the solution ionic strength, was reproduced by the MT theory but not by the empirical regular solution theory (RST). Micellar titration data were also examined in terms of the relative values of the micellar deprotonation equilibrium parameter (pK). The pK was related to the derivative of the electrostatic contribution to the free energy of micellization ( gelec) with respect to . The molecular model of gelec predicted pK > 0 in the limit of micelles composed entirely of the deprotonated form of the pH-sensitive surfactant, consistent with the experimental data. Third, a theory based on RST was developed to model the titration behavior of micelles containing a pH-sensitive surfactant and an arbitrary number of conventional surfactants. The conventional surfactants were successfully modeled as a single eective surfactant, thus considerably simplifying the theoretical analysis of multicomponent surfactant mixtures. The RST description was validated using experimental micellar titration data for single surfactant systems (obtained from the literature) and for binary surfactant mixtures (measured as part of this thesis).
(cont.) Experimental uncertainties in the micellar titration data were examined, and a new method was introduced to account for these uncertainties by using a weighted regression analysis. Fourth, a MT theory was developed to model the micellization of mixtures containing an arbitrary number of conventional surfactants. The maximum micelle radius was examined theoretically for a ternary surfactant mixture. Due to the limited availability of experimental data, only the predicted cmc's were compared with the experimental cmc's. Good agreement was obtained for the predicted cmc's, which were comparable to, and sometimes better than, the cmc's determined using RST. The MT theory was also used to model a commercial nonionic surfactant (Genapol UD-079), which was modeled as a mixture of 16 surfactant components. The predicted cmc agreed remarkably well with the experimental cmc. The monomer concentration was predicted to increase signicantly above the cmc. In addition, the monomer and the micelle compositions were predicted to vary signicantly with surfactant concentration. These composition variations were rationalized in terms of competing steric and entropic eects and a micelle shape transition near the cmc.
(cont.) Finally, the MT theory was further generalized to model the micellization behavior of mixtures of a pH-sensitive surfactant and an arbitrary number of conventional surfactants. Predicted values of the solution pH of mixtures of a pH-sensitive surfactant and an ionic surfactant, as well as of the cmc's of mixtures of two pH-sensitive surfactants, compared favorably with the experimental values. The MT theory was also validated using micellar titration data for varying compositions of mixed micelles containing dodecyldimethylamine oxide (C12DAO) and a cationic, nonionic, or anionic surfactant. The MT theory accurately modeled the titration behavior of C12DAO mixed with the nonionic surfactant. However, C12DAO appeared to interact more favorably with the anionic and the cationic surfactants than waspredicted by the MT theory. The MT theories presented in this thesis represent the rst molecular-based models of the micellization behavior of the following systems: (1) pH-sensitive surfactants, (2) mixtures of three or more conventional surfactants, and (3) mixtures of pH-sensitive surfactants and conventional surfactants. The MT theories resulted in qualitative and quantitative predictions of the micellization properties for a variety of surfactant systems.
(cont.) A simpler theory based on RST was also developed to model titrations of micelles containing pH-sensitive and conventional surfactants. In addition, this thesis resulted in the rst experimental study of the eect of micelle composition on the titration behavior of mixed micelles containing a pH-sensitive surfactant and a conventional surfactant. The resulting MT theories have provided fundamental, physical insight, and they may also decrease the need for the costly and time-consuming process associated with "trial-and-error" surfactant formulation.
by Arthur Clayton Goldsipe.
Ph.D.

The work herein investigates the surface active properties of short peptides and their interactions with conventional surfactants. Short peptides can be designed to mimic the structures of conventional surfactants such as SDS and C12TAB. Such peptide structures include V6K peptide, which are attractive in many fields and applications as they can be more biocompatible, biodegradable and environmentally friendlier substitutes to harsh surfactants. Similar peptide structures can also be found naturally occurring in proteins, such as silk fibroin, and can then be liberated by breaking down the protein into its constituent peptides. The interaction of these peptides with conventional surfactants at the air-liquid and solid-liquid interface have not been investigated before. The adsorption behaviour and structures formed at the solid-liquid interface were examined using Ellipsometry and Neutron Reflection.

The fungus Botrytis cinerea is an opportunistic pathogen on a wide variety of crops, causing disease known as grey mould through infections via wounds or dead plant parts. Synthetic fungicides for controlling this disease are fast becoming ineffective due to the development of resistance. This, coupled with consumers world wide becomng increasingly conscious of potential environment and health problems associated with the build up of toxic chemicals, (particularly in food products), have resulted in pressure to reduce the use of chemical pesticide volumes as well as its residues. An emerging alternative to random synthesis is the study and exploitation of naturally occurring products with fungicidal properties. There have been reports on the uses of synthetic fungicides for the control of plant pathogenic fungi. When utilized in two-way mixtures, such fungicides may maintain or enhance the level of control of a pathogen at reduced rates for both components utilized in combinations, or alone at normal rates. For this study it was hypothesize that the addition of plant extracts may enhance the antifungal efficacy of the synthetic strobilurin fungicide, kresoxim-methyl against Botrytis cinerea.

Surfactants self-assemble into aggregates above a certain concentration. In this work mixtures of the cationic surfactant cetyltrimetylammonium bromide (CTAB) and the anionic surfactant sodium octyl sulfate (SOS) were investigated systematically. The measurements were accomplished by combining the two complimentary techniques static light scattering (SLS) and cryo-transmission electron microscopy (CRYO-TEM). It was found that CTAB-rich samples contain large threadlike micelles rather close to mole fractions where vesicles start to form. The mole fraction x of the surfactant in excess in the aggregates was calculated and it was found that it differs a lot from the mole fraction in the bulk, and the transition from micelles to vesicles occurs when x is about 0.7. In the SOS-rich samples small globular micelles were observed that transform into vesicles upon dilution. Some of the samples rich in SOS were found to contain open vesicles with CRYO-TEM and the reasons for this behavior have been discussed. One question that needs to be further investigated is whether or not these structures are the result of some kind of distortion of the equilibrium process during sample preparation in connection with CRYO-TEM measurements. In most cases the two methods showed consistent results and trends, but for some samples differences could be observed.

Les solvo-surfactants appartiennent à une nouvelle classe de molécules amphiphiles qui présentent à la fois les propriétés de tensioactifs et de solvants. Ils sont en effet capables de former des agrégats et peuvent ainsi solubiliser des composés hydrophobes. De plus, ces molécules présentent une volatilité importante, ce qui les rend particulièrement intéressantes pour des applications où cette propriété est décisive, notamment au cours de la solubilisation aqueuse de parfums. Dans un système solvo-surfactant/huile/eau (SHE), le comportement de phase est fortement influencé par l'hydrophobicité de l'huile. Le nombre équivalent de carbones d'alcane (EACN) de différentes huiles polaires est ainsi étudié. La diminution de l'EACN en comparaison avec les n-alcanes est reliée à leur fonctionnalisation et elle est rationnalisée grâce au paramètre d'empilement effectif. Les EACN de 94 huiles différentes ont été utilisés dans une analyse de régression multilinéaire basée sur les sigma moments de COSMO-RS, dans le but d'établir un modèle QSPR capable de prédire l'EACN d'hydrocarbones. Enfin, l'influence synergique de tensioactifs ioniques sur un système SHE est déterminée avec plusieurs huiles d'EACN différents. Il est montré que le tensioactif ionique augmente fortement la température de stabilité du pseudo système ternaire de même que l'efficacité de solubilisation de l'huile. Cependant, cette efficacité atteint un maximum à un certain ratio molaire en tensioactif ionique car ce dernier empêche le système de s'inverser. Ainsi, une microémulsion bicontinue, connue pour solubiliser une grande quantité d'huile et d'eau, ne peut pas être formée
Solvo-surfactants are a relatively new class of amphiphiles, which exhibit properties of both, surfactants and solvents. They are able to form aggregates, wherein they can solubilise hydrophobic compounds. Furthermore they exhibit volatile characteristics, which make them interesting for applications where volatility is a key factor, such as aqueous fragrance solubilisations. In a solvo-surfactant/oil/water (SOW) system, the phase behaviour is strongly influenced by the hydrophobicity of the oil. Therefore the equivalent alkane carbon number (EACN) of several polar oils, such as dialkylethers, 2-alkanones, 1-chloroalkanes etc. was determined and the decrease in EACN with respect to n-alkanes was related to its functionalization, as well as rationalised with the effective packing parameter for each corresponding type of oil. The EACN of all 94 oils were then used in a multilinear regression analysis, based on COSMO-RS -moments, in order to establish a QSPR model, which is able to predict the EACN of any hydrocarbon oil. The influence of ionic surfactants was finally investigated in a SOW system, with various oils of different EACN. It was found that the ionic surfactant increases strongly the temperature stability of the (pseudo-)ternary system, as well as the efficiency to solubilise the oil. However the efficiency undergoes a maximum for a certain molar fraction of ionic surfactant, since the latter prevents the system to inverse. Thus a bicontinuous microemulsion cannot be formed, which is known to solubilise high amounts of oil and water

The adsorption and the aggregation behaviour of poly(ethylene oxide-b-propylene oxide- b-ethylene oxide) copolymers (EPE) and their mixtures with surfactants of different ionic characters: sodium dodecyl sulphate (SDS), dodecyltrimethylammonium chloride (DTAC) and tetraethylene glycol monooctyl ether (C₈E₄), have been investigated using surface tension and neutron reflection measurements. The first part of the thesis is concerned with the adsorption properties of EPE copolymers at the air-solution interface. The surface tension curves for the copolymers show two breaks similar to those published for Pluronic 3 surfactants (commercially available EPE copolymers). Earlier explanations of this behaviour are inconsistent with the neutron reflection results. The adsorption isotherms obtained by neutron reflection have two steps, one at low concentrations leading to a plateau followed by a substantial rise up to the CMC. The low-concentration breakpoint is attributed to two different effects, the depletion of copolymer molecules in the bulk of the solution and the composition polydispersity. In general, the structure of the adsorbed layer can be described in terms of four layers. The outermost layer is always water free and contains only PO units. The EO residues form tails, which extend into the solution over a distance shorter than the fully extended length. Depending on the conditions, some PO is also found in this tail region. The second part of the thesis is concerned with the effect of mixing EPE copolymers with surfactants of different ionic characters. The formation of mixed micelles and mono layer between EPE 3000-14 and ionic surfactants show a surprisingly strong attractive interaction, which is attributed to a dehydration mechanism. In the mixed micelle formation, in particular, the loss of hydration water molecules found in the micelle core of the copolymer would lead to a substantial gain in entropy. The surface compositions from neutron reflection generally disagree with the predictions of Pseudophase Separation Model. It is believed that changes of hydration upon mixing may be responsible for the deviations as it is not taken into account by the Pseudophase Separation Model. From the neutron reflection studies, DTAC appears to accumulate preferably in the uppermost part of the mixed interfacial layer, while SDS would rather stay in the aqueous phase region. In the C₈E₄/EPE 3000-14 system, the mixed micellization results in strong repulsive interaction, which is attributed to a further hydration of the copolymer micelle core by the incorporation of the solvated C₈E₄ headgroups. However at the air-solution interface, both C₈E₄ and EPE 3000-14 are found to mix ideally. The difference between mixed micelle and mono layer formation observed for such a system is believed to be associated with the structure of the two states. The orientation of the copolymer molecules in the interfacial layer is such that the contact of PO groups with water molecules is significantly reduced. C₈E₄ molecules appeared to adsorb preferentially within the uppermost part of the interfacial layer rich in PO groups.

Esse trabalho teve como objetivo o estudo da toxicidade aguda e crônica da ação isolada e de misturas binárias de três medicamentos veterinários (Monensina, Sulfametazina e Enrofloxacina) para o organismo teste Daphnia magna. A toxicidade aguda da enrofloxacina determinada foi de CE50 - 54.36 mgL-1, da monensina CE50 - 15.11mgL-1 e da sulfametazina CE50 - 183.80 mgL-1. Para os ensaios de toxicidade crônica foram determinados 3 \"endpoints\" (sobrevivência, reprodução e tamanho do adulto) e foi determinado o CEO para a enrofloxacina de 0,33 mgL-1, da monensina 0,09 mgL-1 e da sulfametazina de 6,8 mgL-1. Para fazer uma comparação entre os testes das substâncias isoladas e das misturas binárias foi utilizado o conceito de unidade tóxica (UT), essa comparação foi feita através da soma das UT dos ensaios individuais e comparando com os resultados dos ensaios de misturas para determinar se houve ação sinérgica, aditiva ou antagônica. O ensaio agudo de mistura monensina/enrofloxacina apresentou ação sinérgica já os ensaios monensina/sulfametazina e sulfametazina/enrofloxacina apresentaram ação antagônica. Os ensaios crônicos de mistura monensina/enrofloxacina e monensina/sulfametazina apresentaram ação sinérgica, porém não foram dosedependente e o ensaio sulfametazina/enrofloxacina apresentou ação antagônica. Com base nesse estudo é possível concluir que a mistura desses medicamentos interfere na sua toxicidade, podendo causar efeitos sinérgicos ou antagônicos
This work aims to study the acute and chronic toxicity of the isolated and binary mixtures action of three veterinary drugs (Monensin, Sulfamethazine and Enrofloxacin) for the test organism Daphnia magna. The determined acute toxicity of enrofloxacin was EC50 - 54.36 mgL-1, monensin EC50 - 15.11 mgL-1 and sulfamethazine EC50 - 183.80 mgL-1. In the chronic toxicity tests were determined 3 endpoints (survival, reproduction and adult size) and the LOEC determined for enrofloxacina was 0.33 mgL-1, monensin 0.09 mgL-1 and sulfamethazine 6.8 mgL-1. To make a comparison between the tests of isolated substances and binary mixtures it was used the concept of toxic unit (TU), this comparison was made by adding the UT of individual studies and comparing the test results of mixtures to determine whether there was a synergistic action, additive or antagonistic. The acute mixture assay monensin/enrofloxacin showed synergistic action yet the assays monensin/sulfamethazine and sulfamethazine/enrofloxacin showed antagonistic action. The chronic mixing assays monensin / enrofloxacin and monensin / sulfamethazine showed synergistic action, but were not dose-dependent and testing sulfamethazine / enrofloxacin present antagonistic action. Based on this study it can be concluded that the mixing of these drugs interferes with its toxicity, and may cause synergistic or antagonistic effect

La sensibilité et la sévérité d'explosion des différents mélanges gaz/vapeur-poussière ont été étudiées grâce à des dispositifs standards (sphère de 20 L, tube de Hartmann). Les spécificités des explosions de mélanges hybrides gaz/poussière ont été mises en évidence. En fait, même pour des concentrations de gaz inférieures à la limite inférieure d'explosivité (LIE), la probabilité d'inflammation et la gravité d'explosion peuvent être considérablement augmentées, ce qui permettra notamment de conduire à de grands changements dans la détermination des zones ATEX. Il a été, par exemple, démontré que ces mélanges peuvent être explosifs même lorsque la concentration en poudre et la concentration en vapeur sont respectivement en dessous de la concentration minimale explosive et de la LIE. En outre, des effets de synergie ont été observés et la vitesse de montée en pression de mélanges hybrides peut être supérieure à celles des gaz purs. Les origines de ces spécificités ne doivent pas être recherchées dans la modification d'un paramètre unique, mais peuvent probablement être attribuées aux effets combinés sur l'hydrodynamique (propagation de la flamme), le transfert thermique et la cinétique de combustion. Des expériences ont été menées afin de souligner l'importance de chaque contribution. Basé sur des schémas cinétiques classiques à coeur rétrécissant prenant en compte des diverses contraintes lors d'une réaction non-catalytique de gaz/solide et sur des modèles de combustion homogène pour les gaz, un modèle a été développé pour représenter l'évolution temporelle de la pression d'explosion pour ces mélanges
The explosion sensitivity and severity of various gas/vapor-dust mixtures have been studied thanks to specifically modified apparatuses based on a 20 L sphere and a Hartmann tube. The specificities of gas/dust hybrid mixtures explosions have been highlighted. In fact, even for gas concentrations lower than the lower explosivity limit (LEL), the ignition probability and the explosion severity can be greatly increased, which will notably lead to great changes in the Ex zones determination. For instance, it has been shown that such mixtures can be explosive when both the dust and gas concentrations are below their respective minimum explosive concentration and LEL. Moreover, synergistic effects have been observed and the rate of pressure rise of hybrid mixtures can be greater than those of the pure gases themselves. The origins of these specificities should not be sought in the modification of a single parameter, but could probably be attributed to combined impacts on hydrodynamics (flame propagation), thermal transfer and combustion kinetics. Experiments have been carried out in order to underline the significance of each contribution. Based on classical shrinking core models taking into account the various limitations during a non-catalytic gas/solid reaction and on homogeneous combustion for gases, a model has been developed to represent the time evolution of the explosion pressure for such mixtures

The focus of this thesis has been on the effects of segregation in mixtures of amphiphilic molecules. Two different systems were investigated: fluorocarbon-hydrocarbon surfactant mixtures and lipid-surfactant mixtures.

In fluorocarbon-hydrocarbon surfactant mixtures the repulsive interactions between the chains can lead to a demixing into different types of coexisting micelles, fluorocarbon rich and hydrocarbon rich. From NMR self-diffusion measurements such a demixing was found to occur in the mixture of the partially fluorinated surfactant HFDePC and C₁₆TAC. We furthermore suggested a demixing also within the micelles to explain ¹⁹F-NMR line width data and results from neutron scattering.

In lipid-surfactant mixtures, a segregation of the molecules may instead be caused by a difference in the preferred curvature of the lipid and the surfactant residing within the same aggregate. Using a surfactant selective electrode, binding isoterms of four different cationic surfactants (C₁₂TAC, C₁₄TAC, C₁₆TAC and HFDePC) to preformed lipid (GMO) vesicles were determined. Perforated vesicles were observed by cryo-TEM in the mixture with C₁₆TAC. To explain the results from the binding isoterms, the formation of pores in the bilayer was regarded as a cooperative process, similar to micelle formation. The surfactant accumulates at the edges of the pores, and increasing the surfactant concentration results in an increased number of pores with a constant surfactant/lipid ratio at the edges.

The lipid-surfactant mixtures were also studied at the solid/solution interface using AFM. An adsorbed mesh structure, a counterpart to the bulk perforated lamellar phase, was observed for the first time.

O trabalho desenvolvido teve como objetivo estudar a solvatação em misturas binárias de água com líquidos iônicos, LIs, destacando a influência da lipofilicidade e estrutura deste últimos. Além disso, estudou-se uma série inédita de líquidos iônicos tensoativos, LITs, cujas propriedades em solução aquosa, foram determinadas através de diversas técnicas experimentais. Em relação aos LIs, os estudo iniciou-se com a síntese, purificação e caracterização dos cloretos de 1-alil-3-alquilimidazólios, e posteriormente, analisou-se a solvatação pelas referidas misturas binárias. Para este estudo, foram utilizados compostos (sondas solvatocrômicas) cujos espectros Uv-Vis são sensíveis às propriedades do meio. Juntamente com tais sondas, aplicou-se um modelo de solvatação preferencial, proposto pelo grupo, que descreve a solvatação da sonda, considerando os dois solventes e um “complexo” água-LI. O estudo de solvatocromismo envolveu a utilização de três sondas, MePMBr2, OcPMBr2 e MeQMBr2 e três líquidos iônicos, AlMeImCl, AlBuImCl e AlHxImCl, visando a compreensão das interações hidrofóbicas, o efeito de anelação e o aumento da cadeia alquílica. Os resultados mostraram a importância de várias interações sonda-LI, incluindo ligações de hidrogênio, eletrostáticas, e hidrofóbicas, para a solvatação das sondas. Em relação aos LITs, a série estudada, cloretos de 1-metil-3(3-acilaminopropil) imidazólio, foi sintetizada, purificada e caracterizada. As propriedades das soluções de tensoativos em soluções aquosas foram determinadas através das técnicas de condutância, tensão superficial, espalhamento estático de luz e solvatocromismo. Os valores de concentração micelar crítica, cmc, e energia livre de Gibbs de micelização, ΔGmic, obtidos através das três primeiras técnicas citadas, foram comparados com os valores dos cloretos de 1-metil-3-alquilimidazólio, (tensoativos análogos aos estudados, exceto pela ausência do grupo propilamida) e mostraram que a presença da amida, favorece o processo de micelização, uma vez que os valores dos dois parâmetros citados foram menores para os tensoativos estudados. No estudo de solvatocromismo em soluções micelares, foram utilizadas as sondas WB, 4-nitroanisol, 4-nitroanilina e N,N-dimetil-4-nitroanilina. Com estas sondas foi possível estudar a acidez, α, basicidade, β, polarizabilidade, π* e concentração da água interfacial, [água]interfacial. Notou-se que , α,β, [água]interfacial, diminuíram com o aumento da cauda hidrofóbica do tensoativo, devido a maior proximidade entre os grupos hidrofílicos diminuindo a área mínima das cabeças. Tal diminuição comprime as cabeças dos tensoativos, e atenua a disponibilidade do H2 ácido do imidazol, justificando a diminuição de α com o aumento da hidrofobicidade do tensoativo.
The developed work focused the study of the solvation of binary mixtures among water and ionic liquids, ILs. Highlighting the influence of the lipophilicity and structure of the ILs. Moreover, it was studied a new series of surface active ionic liquids, SAILs, and the properties of these SAILs in water, was studied using many experimental techniques. The ILs study started with the synthesis, purification and characterization of the 1-allil-3-alkylimidazolium chlorides, and after, it was studied the solvation of the aqueous binary mixtures. In this study, they were utilized solvatochromic probes, these substances are sensitive to the medium properties, and can be analyzed using the Uv-Vis spectroscopy. In order to explain the obtained results, it was applied a solvation model, developed by the research group. This model describes the solvation considering the presence of the two solvents and a “:complex” water-IL. The solvatochromic study was utilized three probes, MePMBr2, OcPMBr2 e MeQMBr2 and three ILs, AlMeImCl, AlBuImCl e AlHxImCl. The results showed the importance of probe-LI interaction, for example, hydrogen bond, electrostatic and hydrophobic interactions; that influences the solvation of the probe. The SAILs studied series, was the 1-methyl-3(3-acylaminopropyl) imidazolium chloride, this series was synthesized, purified and characterized. The properties of the surfactants aqueous solutions were investigate with conductance, surface tension, light scattering and solvatochromism. The values of critical micelle concentration, cmc, and Gibbs free energy, ΔGmic, was obtained with the first three techniques, and these results were compared with the series 1-methyl-3-alkylimidozolium chlorides. The results showed that the presence of the amide functional group support the micellization process. In the solvatochromic study of micellar solutions, they were utilized the probes WB, 4-nitroanisole, 4-nitroaniline e N,N-dimethyl-4-nitroaniline. Using these probes, it was possible to determine the acidity, α, basicity, β, polarizability, π* and interfacial water concentration, [water]interfacial. It was observed, that α, β and [water]interfacial decreased with the increase of the hydrophobic chain of the surfactant.

Orientador: Edvaldo Sabadini
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: O estudo de soluções para métodos especiais de recuperação de petróleo vem sendo amplamente utilizado, principalmente devido à grande quantidade de óleo remanescente nos reservatórios após as recuperações primária e secundária. Soluções consideradas de potencial recuperador devem possuir algumas características específicas como uma baixa tensão interfacial água/óleo e viscosidade moderada, de modo a melhorar a eficiência do petróleo varrido. Interações fluidos-rocha e óleo-rocha são determinantes no montante de óleo a ser recuperado, assim sendo, estudos com relação à molhabilidade das superfícies das rochas mostram-se fundamentais. Um método de análise largamente empregado e considerado como padrão para medidas de molhabilidade é o teste de Amott, porém, tal método apresenta grande tempo de análise e preparo de amostra. O presente trabalho analisa a molhabilidade de rochas utilizando-se a técnica de Ressonância Magnética Nuclear de Baixo Campo. Ela se baseia nos tempos de relaxação da magnetização das populações de água e óleo, livres ou ligadas na superfície da rocha, permitindo de maneira rápida, a determinação da quantidade de óleo removida. Nesse estudo foram analisadas amostras de arenito e carbonato, caracterizando-as comparativamente com relação ao tamanho e homogeneidade dos poros por dados de RMN. As rochas foram impregnadas com petróleo e deixadas em contato com diferentes soluções de surfactantes (não iônico e zwiteriônico), sendo possível a análise quanto à diferença de molhabilidade entre as mesmas. Com relação a essas soluções, foram utilizados diversos surfactantes, com diferenças quanto aos grupos funcionais, ao tamanho da cadeia hidrofóbica, a presença de uma ou duas dessas cadeias e em diferentes concentrações, sendo possível a obtenção de informações relacionadas à eficiência de extração de óleo para cada uma delas. Observou-se que a técnica utilizada apresentou excelentes resultados, permitindo diferenciar a capacidade de extração para cada solução estudada
Abstract: The study of solutions to enhance oil recovery has been widely used, mainly due to large amount of oil that remains in reservoirs after primary and secondary recoveries. Solutions with good potential to recovery must have some specific characteristics such as low water/oil interfacial tension and a moderate viscosity to improve the efficiency of the oil swept. The fluid-rock and oil-rock interactions are of great importance concerning the total oil recovered. Therefore, studies involving wettability of rock surfaces are essential. A traditional method of analysis, which is considered as standard to measures the wettability is the Amott test, however, this method spends too much time and sample preparation. This study analyzes rock wettability using the technique of Low Field Nuclear Magnetic Resonance (low-field NMR). This is based on the relaxation rates of the magnetization of water and/or oil molecules, free or bounded at the surface of the pores of the rock. The technique allows a quick determination of the amount of oil removed. In the present study, the size and pores homogeneity of sandstone and carbonate were analyzed using low field-NMR. The rocks were impregnated with oil and then left in contact with different solutions of surfactants (non-ionic and zwitterionic), being possible to analyze the differences in wettability among them. Several concentrations of surfactants, in which differences in their: functional groups, hydrophobic chain length and number of chains, were studied. The NMR technique revealed excellent results, providing information related to the efficiency of oil extraction for each studied solution
Mestrado
Físico-Química
Mestre em Química

碩士
臺北醫學大學
生醫材料暨工程研究所
97
Although there were studies suggest that the combination of antioxidants may effectively enhance free radical scavenging efficacy and may exert some synergistic effect, there is still no in-depth research in this area regarding the relationship between the compositions of the ingredients, their concentrations and ratios, and whether they may result in synergistic antioxidative effect. Many commercial anti-aging and antioxidative products are mixtures of various antioxidants, but there is no study yet today to provide in which composition of the antioxidant mixtures is the most optimal formulation for antioxidant. The purpose of this study is to investigate the potential synergistic relationship between various combinations of the four antioxidants: vitamin E, vitamin C, lutein/zeaxanthin, and green tea polyphenol (EGCG). The antioxidative ability of the antioxidants was evaluated by the DPPH method. An experimental design software was introduced in this study to construct the conditions of the 2-component, 3-component, and 4-component antioxidant combinations. The synergistic effect of the antioxidant combination was evaluated mathematically using two calculation modes. Our results showed that the combination of vitamin E, vitamin C, and green tea polyphenol (2-component or 3-component) exerted synergistic antioxidative effect. However, the combination of all the 4 components did not provide synergistic antioxidative effect.

碩士
國立成功大學
化學工程學系
86
It can be found in many surfactant applications that they give much stronger surface activities than single surfactant components. This phenomena is normally called synergism. In this work the synergism of surface tension reduction and micelle formation in anionic/cationic surfactant mixtures(SDS/CPC) is studied by using surface tension method. The heat change and the mechanism of micelle formation are also studied by using of isothermal titration calorimetry method. The experiment results show that SDS/CPC mixed surfactant systems have strong synergistic effect in surface tension reduction and micelle formation. The interaction parameters, bs for mixed monolayer on the air/water interface ,and bm for mixed micelles, have large negative values. This show that the molecular interactions are attractive forces. By the measurement of surface tension reduction with time, we found that surfactant mixtures have obvious dynamic adsorption behavior. For the case of pure surfactants, micellization is endothermic. Because the values of free energy change, calculated by mass-action model are positive, the micellization process is spontaneous. And the thermodynamic principles show that, micellization is an entropy driven process. In mixed systems, the SDS/TX-100(1/1) mixtures has no obvious synergism, and its behavior are dominated by TX-100. In SDS/CPC(1/1) mixtures, because of the strong ionic- bond interactions , the result can not be analysis.

碩士
國立成功大學
化學工程學系
88
In this work, catanionic surfactants of CP‧DS and DTMA‧DS were prepared by mixing equimolar CPC and DTMAC solutions, respectively, with SDS solutions and followed by separation and purification processes including centrifugal filtration, washing, and vacuum drying. The solid precipitate was subsequently subjected to analyses with elemental analyzer (EA), mass spectrometer (MASS), and Fourier transform infrared spectrometer (FTIR) for chemical structure identification. The results of EA reveal the solid precipitates contain finite elements which have constant weight percent including C、H、O、N、S. The molecular weights are determined to be 570 and 494 g/mole, respectively, for CP‧DS and DTMA‧DS by MASS. Some marked groups of the solid precipitates can be found by FTIR. These results lend evidence to the formation of catanionic surfactants by anionic and cationic surfactants in equimolar. In addition, the surface activities of these two catanionic surfactants were also measured. The data were measured by maximum bubble pressure tensiometer show the dynamic adsorption behaviors of CP‧DS and DTMA‧DS are similar to pure water. CP‧DS and DTMA‧DS with high surface activities were also measured and compared with those observed by equilibrium surface tensions for solutions of the single and binary mixed surfactants. With the appropriate theoretical models, we can calculate the equilibrium adsorption parameters (such as m、KL) and investigate the equilibrium adsorption behaviors of CP‧DS and DTMA‧DS. As for the dynamic adsorption behaviors of these two catanionic surfactants, experimental results with the theoretical analysis show that the dynamic adsorption processes of CP‧DS and DTMA‧DS are diffusion controlled.

lthough extensive research work has been carried out on the drag reduction behavior of polymers and surfactants alone, little progress has been made on the synergistic effects of combined polymers and surfactants. A number of studies have demonstrated that certain types of polymers and surfactants interact with each other to form surfactant-polymer complexes. The formation of such complexes can cause changes in the solution properties and may result in better drag reduction characteristics as compared with pure additives. A series of drag-reducing surfactants and polymers were screened for the synergistic studies. The following two widely used polymeric drag reducing agents (DRA) were chosen: a copolymer of acrylamide and sodium acrylate (referred to as PAM) and polyethylene oxide (PEO). Among the different types of surfactants screened, a cationic surfactant octadecyltrimethylammonium chloride (OTAC) and an anionic surfactant Sodium dodecyl sulfate (SDS) were selected for the synergistic study. In the case of the cationic surfactant OTAC, sodium salicylate (NaSal) was used as a counterion. No counterion was used with anionic surfactant SDS. The physical properties such as viscosity, surface tension and electrical conductivity were measured in order to detect any interaction between the polymer and the surfactant. The drag reduction (DR) ability of both pure and mixed additives was investigated in a pipeline flow loop. The effects of different parameters such as additive concentration, type of water (deionized (DI) or tap), temperature, tube diameter, and mechanical degradation were investigated. The addition of OTAC to PAM solution has a significant effect on the properties of the system. The critical micelle concentration (CMC) of the mixed surfactant-polymer system is found to be different from that of the surfactant alone. The anionic PAM chains collapse upon the addition of cationic OTAC and a substantial decrease in the viscosity occurs. The pipeline flow behaviour of PAM/OTAC mixtures is found to be consistent with the bench scale results. The drag reduction ability of PAM is reduced upon the addition of OTAC. At low concentrations of PAM, the effect of OTAC on the drag reduction behavior is more pronounced. The drag reduction behavior of polymer solutions is strongly influenced by the nature of water (de-ionized or tap). The addition of OTAC to PEO solution exhibited a week interaction based on the viscosity and surface tension measurements. However, the pipeline results showed a considerable synergistic effect, that is, the mixed system gave a significantly higher drag reduction (lower friction factors) as compared with the pure additives (pure polymer or pure surfactant). The synergistic effect in the mixed system was stronger at low polymer concentrations and high surfactant concentrations. Also the resistance against mechanical degradation of the additive was improved upon the addition of OTAC to PEO. The mixed PEO/SDS system exhibited a strong interaction between the polymers (PEO) and the surfactant (SDS), Using electrical conductivity and surface tension measurements, the critical aggregation concentration (CAC) and the polymer saturation point (PSP) were determined. As the PEO concentration is increased, the CAC decreases and the PSP increase. The addition of SDS to the PEO solution exhibits a remarkable increase in the relative viscosity compared to the pure PEO solution. This increase is attributed to the changes in the hydrodynamic radius of the polymer coil. The pipeline flow exhibited a considerable increase in DR for the mixed system as compared to the pure PEO solution. The addition of surfactant always improves the extent of DR up to the PSP. Also the mixed PEO/ SDS system shows better resistance against shear degradation of the additive.

Videomicroscopy was used to measure rates of solubilization of triolein drops injected into thin, rectangular glass cells containing solutions of nonionic surfactants and their mixtures with alcohols at various temperatures. In most cases the solubilization rate per unit area was independent of time and of initial drop size. This indicates that processes occurring at the interface control the rate of solubilization. The solubilization rate can be increased by increasing the flexibility of the surfactant films either by adding short-chain alcohols or by using a surfactant mixture with a thinner and less ordered hydrocarbon chain region. Videomicroscopy was also used to investigate the mechanisms and rates of dissolution of neat, liquid nonionic surfactants in water. A microinjection technique was used to produce drops of pure C$\sb{12}$E$\sb5$ and C$\sb{12}$E$\sb6,$ which dissolved rapidly at temperatures below their cloud points. The results indicated that the process was diffusion controlled. Estimates of effective binary diffusion coefficients in the intermediate liquid crystalline phase(s) which formed were obtained by combining their measured growth rates in one-dimensional experiments where neat surfactant contacted water with measured dissolution times of surfactant drops. Drops of the commercial nonionic surfactants Neodol 25-7 and Tergitol 15-S-7 required considerable time for complete dissolution at temperatures just below their cloud points. Considerable spontaneous emulsification of water in the surfactant drops was also observed. Moreover, the final small drops frequently became elongated and sometimes formed conical projections that emitted jets. Similar behavior was seen for the model system C$\sb{12}$E$\sb8$/n-decanol/water and occurs because the more hydrophilic component dissolves more rapidly. At 30$\sp\circ$C a compact mass of viscous myelinic figures developed when a drop of C$\sb{12}$E$\sb4$ was injected into water. However, complete dissolution occurred when 5 wt% of small SDS crystals was added to the drop. Here too considerable spontaneous emulsification, elongation, and some jetting were observed. Complete dissolution also occurred when C$\sb{12}$E$\sb4$ drops were injected into dilute SDS solutions. However, dissolution was much slower when the SDS concentration was large enough that hexagonal and cubic intermediate phases formed in addition to the lamellar phase which was seen in all cases.

碩士
嘉南藥理大學
化粧品應用與管理系
103
Skin whitening has invariably been a skin effect desired among Asian women. Overexpression and accumulation of melanin influence the overall aesthetics of a person and easily induce various types of skin pigmentation diseases. Tyrosinase is a key enzyme for melanin synthesis. Inhibiting the activity of this enzyme and accelerating the metabolism of melanocytic skin cells yield skin-whitening effects. In this study, α-arbutin, L-ascorbic acid, hydroquinone, kojic acid, magnesium ascorbyl phosphate, sodium ascorbyl phosphate, and tranexamic acid were used. The inhibitory effects that mixtures containing either two of the aforementioned substances have on tyrosinase activity were investigated under varying pH conditions ( pH=3~8 ). Subsequently, the effects of these mixtures on cytotoxicity and intracellular tyrosinase activity were determined. The experimental results showed that the samples most of the optimally inhibited the activity of mushroom tyrosinase under a pH condition of 3. Mixing kojic acid with hydroquinone exerted a synergistic effect; in addition, when 0.7% kojic acid was mixed with 0.3% hydroquinone, the optimal mixing effect under the same final concentration was achieved. For this mixture, the cytotoxicity test revealed that the toxicity of hydroquinone decreased with increasing proportion of kojic acid. The test results for intracellular tyrosinase activity showed that this aspects also decreased as the proportion of kojic acid was increased.

碩士
國立屏東科技大學
植物醫學系所
104
The brown Planthopper (BPH), Nilaparvata lugens is a major pest of rice production in tropical Asia. In many countries, BPH causes serious economic loss on rice yield by sucking rice sap and transmitting various of rice virus diseases. The appearance of insecticide resistance challenges the control of BPH in field. The development of new insecticide is expensive and time-consuming. Thus, the precise and proper use of existing compounds becomes an important issue in resistance management of this pest. Pesticide rotation is an effective approach in resistance management. However, practice of pesticide rotation is not accustomed for traditional farmers, and this strategy also is inappropriate to the pest which developed multiple resistances. In this study, five commercial insecticides of BPH (Chlorpyrifos, Permethrin, Imidacloprid, Clothianidin and Thiamethoxam) were tested by rice seedling dipping bioassay method to explore the toxicity of the binary mixture between various kinds of insecticides. Base on the results of estimated Combination Index (CI), mixture of Chlorpyrifos and Neonicotinoids showed antagonistic effect in all combinations. The mixtures of Permethrin and Neonicotinoids showed synergistic (CI<1) and additive effect (CI=1) in most of cases. The mixtures of Chlorpyrifos/Permethrin displays synergistic effect at three different mixture ratio (1:1、1:10 and 10:1). The strongest synergism observed in Chlorpyrifos/ Permethrin mixtures at 1:1 ratio (CI=0.39). The Results of field trails showed the mixture of Chlorpyrifos 50ppm + Permethrin 50ppm increased the field control efficiency significantly rather than solo treatment of Chlorpyrifos or Permethrin. The result showed the mixture of Chlorpyrifos and Permethrin showed more than 86% control rate during the period of 1 to 14 days after spraying. Addition of enzyme inhibitor followed by detoxification enzyme activity assays suggested that the mechanism of synergistic effect of Chlorpyrifos/Permethrin mixture may result from the cytochrome P450 and esterase active site competition between Chlorpyrifos and Permethrin; Analysis of CYP(cytochrome P450) gene expression revealed that, when BPH treated with binary mixtures of Chlorpyrifos and Permethrin, the expression of NlCYP303A1 were significantly decreased compare with Chlorpyrifos or Permethrin treatment. This finding indicated that, the insecticide-induced up-regulation of CYP gene might be interfered by mixture of insecticides. This phenomenon provided some issues about the mechanism of synergistic effect between organophosphate and pyrethroid in future work.

碩士
國立交通大學
材料科學與工程學系所
102
In this study we prepared novel composites materials from the hydrogen-bonded bent-core liquid crystal (LC) host and different mole ratios (0–90 mol%) of the surface-modified fullerenes(C60). The chemical structures of these compounds were characterized by 1H-NMR, 13C-NMR, IR spectra, MS as well as elemental analysis, and the liquid crystalline phases and mesomorphic behavior of all the compounds were identified from the results of DSC, POM, electro-optical measurement and XRD. The mesomorphic properties of the composites, including their mesophasic types and ranges, values of Ps, and saturated electric field were adjustable by varying the doping concentrations of fullerenes. By increasing the concentration of fullerenes, the polarity of the SmCP phase in the composite varied sequentially from anti-ferroelectricity to ferroelectricity. Futhermore, adding a little amount of surface-modified fullerenes make the mixtures possesses the best Ps value and saturated electric field.