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Aggregation and micellization of sodium dodecyl sulfate in the presence of Ce(III) at different temperatures: A conductometric study

Valente, Artur J. M.; Burrows, Hugh D.; Cruz, Sandra M. A.; Pereira, Rui F. P.; Ribeiro, Ana C. F.; Lobo, Victor M. M.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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Aggregation properties of sodium dodecyl sulfate (SDS) in the presence of cerium(III) chloride, at various temperatures (298.15-323.15 K) have been measured by the electrical conductance technique. The experimental data on aqueous solutions as a function of SDS concentration show the presence of two inflexion points indicating the presence of two distinct interaction mechanisms: the first, occurring at SDS concentrations below the critical micelle concentration of the pure surfactant, which can be explained by the formation of aggregates between dodecyl sulfate (DS-) and Ce(III), while the second one, at SDS concentrations around the critical micelle concentration (cmc) of the pure surfactant which is due to the SDS micellization. The aggregation between DS- and Ce(III) was confirmed by static light scattering. The binding ratio of DS-/Ce(III) changes from 6 to 4, shows a slight dependence on the Ce(III) concentration and is independent of the temperature. The thermodynamic micellization parameters, Gibbs energy, enthalpy and entropy of micellization were calculated on the basis of the experimental data for the aggregation concentration, and the degree of counterion dissociation of the micelles. The SDS micellization is energetically favoured by increasing either the concentration of CeCl3 or the temperature. Such behaviour is clearly dominated by a decrease of the micellization (exothermic) enthalpy. The entropy of micellization approaches zero as the cerium(III) chloride concentration and temperature increase.; http://www.sciencedirect.com/science/article/B6WHR-4S6G90R-1/1/a864220de360ed7b600885de2f94b119

Effect of terbium(III) chloride on the micellization properties of sodium decyl- and dodecyl-sulfate solutions

Neves, A. C. S.; Valente, A. J. M.; Burrows, H. D.; Ribeiro, A. C. F.; Lobo, V. M. M.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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The effect of TbCl3 on the aggregation processes of the anionic surfactants sodium decyl sulfate (SDeS) and sodium dodecyl sulfate (SDS) has been investigated. Electrical conductivity data, combined with Tb(III) luminescence measurements suggest that the formation of micelles involving TbCl3 and SDS occurs at concentrations below the critical micelle concentration (cmc) of the pure surfactants; the formation of these mixed aggregates was also monitored by light scattering, which indicates that the addition of TbCl3 to surfactant concentration at values below the pure surfactant cmc results in a much greater light scattering than that found with pure sodium alkylsulfate surfactant micelles. This phenomenon is dependent upon the alkyl chain length of the surfactant. With Tb(III)/DS-, complexes are formed with a cation/anion binding ratio varying from 3 to 6, which depends upon the initial concentration of Tb(III). This suggests that the majority of the cation hydration water molecules can be exchanged by the anionic surfactant. When the carbon chain length decreases, interactions between surfactant and Tb(III) also decrease, alterations in conductivity and fluorescence data are not so significant and, consequently, no binding ratio can be detected even if existing. The surfactant micellization is dependent on the presence of electrolyte in solution with apparent cmc being lower than the corresponding cmc value of pure SDS.; http://www.sciencedirect.com/science/article/B6WHR-4M6RXJ6-1/1/1def21af9db31ec7f144102b9f17a9be

Termodinamica de micelização de alquilglicosideos em H2O e em D2O; Thermodynamics of micellization of alkylglucosides in H2O and D2O

Rodrigo Giatte Angarten
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/09/2007 PT
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Alquilglicosídeos (AG) são surfatantes não-iônicos totalmente provenientes de fontes naturais e renováveis, além de serem totalmente biodegradáveis e atóxicos. Neste trabalho estudou-se a termodinâmica de micelização desta classe de surfatantes através das técnicas de calorimetria diferencial de varredura (DSC) e titulação calorimétrica isotérmica (ITC), em função do número de átomos de carbono presentes em sua cadeia hidrofóbica e do número de unidades glicosídicas em sua parte polar. Estas propriedades foram determinadas em H2O e em D2O. Para um mesmo AG, o aumento de temperatura implica em uma energia de Gibbs, DmicG, mais favorável à micelização. Com o aumento de temperatura, a variação de entalpia, DmicH, passa de positiva para negativa e o termo entrópico, TDmicS, perde sua contribuição para a micelização. Quando comparados surfatantes de mesmo número de átomos de carbono na cadeia alquílica, mono e di-glicosídeos apresentam estritamente o mesmo comportamento termodinâmico. Heptilglicosídeo apresentou comportamento distinto dos demais surfatantes estudados, indicando que o ambiente químico no interior de sua micela é diferente. Estudos da micelização nos dois solventes mostraram que a maior energia coesiva de D2O...

Estudo termodinâmico de associação de surfatantes zwitteriônicos e sua interação com polímeros através de titulação calorimétrica; Thermodynamic study of zwitterionic surfactants self-assembly and its interaction with polymers by calorimetry titration

César Brinatti Antonio
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2011 PT
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As sulfobetaínas (SB) são uma classe de surfatantes zwitteriônicos. A presença de grupos carregados tanto positiva quanto negativamente na mesma molécula concede à sua cabeça polar uma hidrofilicidade intermediária entre surfatantes iônicos e não-iônicos. O estudo termodinâmico de associação da série homóloga de sulfobetaínas, bem como sua interação com polímeros iônicos e não-iônicos, foi feito utilizando a técnica de titulação calorimétrica isotérmica (ITC), em diferentes temperaturas. O aumento da temperatura leva a um valor mais negativo de energia livre de Gibbs de micelização DmicG, o que favorece a micelização. O termo entrópico TDmicS, embora sempre positivo, é o responsável pela micelização em baixas temperaturas. No entanto, com o aumento da temperatura este termo perde sua intensidade, enquanto o termo entálpico DmicHinverte seu sinal, de positivo para negativo, superando em intensidade o termo entrópico, sendo então o responsável pela micelização em temperaturas elevadas. No estudo de interação com polímeros não-iônicos, o poli (ácido acrílico), PAA, induziu a formação de agregados de unímeros de surfatantes em concentrações abaixo de sua cmc, enquanto o poli (óxido de propileno)...

Influence of lipid chain unsaturation on melittin-induced micellization.

Monette, M; Lafleur, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1996 EN
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It is well known that melittin, an amphipathic helical peptide, causes the micellization of phosphatidylcholine vesicles. In the present work, we conclude that the extent of micellization is dependent on the level of unsaturation of the lipid acyl chains. We report the results obtained on two systems: dipalmitoylphosphatidylcholine (DPPC), containing 10(mol)% saturated or unsaturated fatty acid (palmitic, oleic, or linoleic), and DPPC, containing 10(mol)% positively charged diacyloxy-3-(trimethylammonio)propane bearing palmitic or oleic acyl chains. For both systems, the presence of unsaturation in the lipid acyl chains inhibits melittin-induced micellization. Conversely, the addition of saturated palmitic acid to the DPPC matrix enhances the micellization. This modulation is proposed to be associated with the cohesion of the hydrophobic core. When the lipid chain packing of the gel-phase bilayer is already perturbed by the presence of unsaturation, it seems easier for the membrane to accommodate melittin at the interface, and the distribution of the peptide in the bilayer could be the origin of the inhibition of the micellization. The cohesion of the apolar core is shown to play an unquestionable role in melittin-induced micellization; however...

Microwave-assisted synthesis and micellization behavior of soy-based copoly(2-oxazoline)s

Hoogenboom, Richard; Leenen, Mark A. M.; Huang, Haiying; Fustin, Charles-André; Gohy, Jean-François; Schubert, Ulrich S.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
EN
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Polymers based on renewable resources are promising candidates for replacing common organic polymers, and thus, for reducing oil consumption. In this contribution we report the microwave-assisted synthesis of block and statistical copolymers from 2-ethyl-2-oxazoline and 2-“soy alkyl”-2-oxazoline via a cationic ring-opening polymerization mechanism. The synthesized copolymers were characterized by gel permeation chromatography and 1H-NMR spectroscopy. The micellization of these amphiphilic copolymers was investigated by dynamic light scattering and atomic force microscopy to examine the effect of hydrophobic block length and monomer distribution on the resulting micellar characteristics.

Novel pH Responsive Amphiphilic Diblock Copolymers with Reversible Micellization Properties

Palaniswamy, R.; Dai, S.; Tam, Michael K. C.; Gan, L.H.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 284986 bytes; application/pdf
EN_US
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Di-block copolymer of poly[methacrylic acid-block-2-(diethylamino)ethyl methacrylate] [P(MAA-b-DEA)] with narrow molecular weight distribution was synthesized using the atom transfer radical polymerization (ATRP) technique. The micellization behavior of the P(MAA-b-DEA) copolymer in aqueous solution at room temperature and different pH values were examined by potentiometric and conductivity titration, UV-Visible spectrophotometry, ¹H-NMR, static and dynamic laser light scattering. At low pH (< 4.2), core-shell micelles were formed with MAA core and protonated DEA shell. At moderate pH values, the polymer precipitated from water and formed a cloudy solution, where the polymer chains aggregated into larger particles resembling that of a hard sphere induced by electrostatic interactions. At high pH (> 9.5), core-shell like micelles consisting of hydrophobic DEA core and ionized MAA shell were re-established.; Singapore-MIT Alliance (SMA)

Complementary use of computer simulations and molecular-thermodynamic theory to model surfactant and solubilizate self-assembly

Stephenson, Brian C. (Brian Curtis)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (769 p.)
ENG
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Surfactants, or surface active agents, are used in many pharmaceutical, industrial, and environmental applications. Selection of the appropriate surfactant or mixture of surfactants for any given application is driven by the need to control bulk solution micellization and solubilization characteristics. The goal of this thesis has been to develop computer simulations and molecular-thermodynamic modeling approaches to predict these solution characteristics based on knowledge of surfactant and solubilizate chemical structure. The ability to make such predictions would give formulators in industry the ability to design and optimize surfactant formulations with a minimum of effort and expense. This thesis has explored the application of three theoretical approaches to model surfactant micellization and micellar solubilization. The first theoretical approach involves the use of computer simulations (CS) to obtain input parameters for molecular-thermodynamic (MT) modeling of surfactant micellization and micellar solubilization. This approach was motivated by the limitations inherent in computer simulations (the high computational expense of modeling self-assembly) and in MT modeling approaches (their restriction to structurally and chemically simple surfactants and solubilizates).; (cont.) A key input required for traditional MT modeling is the identification of the hydrated and the unhydrated portions (head and tail) of surfactants and solubilizates in a self-assembled micellar aggregate. By conducting simulations of surfactants and solubilizates at an oil/water interface (modeling the micelle core/water interface) or in a micellar environment...

A computer simulation and molecular-thermodynamic framework to model the micellization of ionic branched surfactants in aqueous solution

Lin, Shangchao
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 132 leaves
ENG
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Surfactants, or surface active agents, are chemicals exhibiting amphiphilic behavior toward a solvent. This amphiphilic character leads to increased activity at interfaces and to self-assembly into micellar aggregates beyond a threshold surfactant concentration, referred to as the critical micelle concentration (CMC), in bulk solutions. As a result of these unique attributes, surfactants are used in many pharmaceutical, industrial, and environmental applications, including biological separations, fat metabolism during digestion, drug delivery, and water purification. Selection of the appropriate surfactant for a given application is often motivated by the need to control bulk solution micellization properties, such as the CMC and the micelle shape and size. The ability to make molecular-level predictions of these surfactant properties would allow formulators in industry to speed up the design and optimization of new surfactant formulations. In this thesis, a combined computer simulation/molecular-thermodynamic (CS-MT) modeling approach was developed and utilized to study the micellization behavior of ionic branched surfactants, which are a class of surfactants of great industrial relevance in applications such as detergency, emulsification...

Molecular-thermodynamic theories of micellization of multicomponent surfactant mixtures and of pH-sensitive surfactants

Goldsipe, Arthur Clayton
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 264 p.; 1538384 bytes; 1581044 bytes; application/pdf; application/pdf
ENG
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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...

Theoretical modeling of micellization and solubilization in ionic surfactant systems

Srinivasan, Vibha, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 389 p.; 16244919 bytes; 28280975 bytes; application/pdf; application/pdf
ENG
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Ionic surfactants constitute a very important class of surfactants, both from an academic as well as from a commercial viewpoint. In most commercial applications involving ionic surfactants, the selection of the surfactant is based on its aqueous bulk solution properties, including its micellization characteristics and its micellar solubilization characteristics (that is, the capacity of the surfactant micelles to encapsulate hydrophobic solutes in their interior, leading to a significant increase in the aqueous solubility of the hydrophobic solutes). Accordingly, the development of comprehensive, predictive, molecularly-based theories that relate the bulk solution properties of an ionic surfactant to its chemical structure should facilitate significantly the rational design, selection, and optimization of commercial surfactant formulations. The first major contribution of this thesis was the development of a molecular-thermodynamic theory of micellization of ionic surfactant-electrolyte systems, which takes into account the possibility that counterions (inorganic or organic, monovalent or multivalent) released by the ionic surfactant polar heads and by any added electrolytes can bind onto the charged micelle surface. By minimizing the free energy of micellization...

Effect of phenol on the aggregation characteristics of an ethylene oxide-propylene oxide triblock copolymer P65 in aqueous solution

Jitendrakumar, Mata; Majhi, P R; Kubota, O; Khanal, A; Nakashima, K; Bahadur, P
Fonte: Academic Press Publicador: Academic Press
Tipo: Artigo de Revista Científica
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The effects of phenol on the micellization, micellar growth, and phase separation of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic P65: EO19PO30EO19) in aqueous solution have be

Micellization in the presence of polyelectrolyte

Lemke, N.; Arenzon, Jeferson J.; Levin, Yan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/03/2001
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We present a simple model to study micellization of amphiphiles condensed on a rodlike polyion. Although the mean field theory leads to a first order micellization transition for sufficiently strong hydrophobic interactions, the simulations show that no such thermodynamic phase transition exists. Instead, the correlations between the condensed amphiphiles can result in a structure formation very similar to micelles.; Comment: 8 pages, 7 figures

Three eras of micellization

Neu, J. C.; Cañizo, J. A.; Bonilla, L. L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 04/11/2002
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Micellization is the precipitation of lipids from aqueous solution into aggregates with a broad distribution of aggregation number. Three eras of micellization are characterized in a simple kinetic model of Becker-D\"oring type. The model asigns the same constant energy to the $(k-1)$ monomer-monomer bonds in a linear chain of $k$ particles. The number of monomers decreases sharply and many clusters of small size are produced during the first era. During the second era, nucleii are increasing steadily in size until their distribution becomes a self-similar solution of the diffusion equation. Lastly, when the average size of the nucleii becomes comparable to its equilibrium value, a simple mean-field Fokker-Planck equation describes the final era until the equilibrium distribution is reached.; Comment: 21 pages, 6 figures, to appear in Phys. Rev. E

Thermodynamics of micellization of oppositely charged polymers

Castelnovo, Martin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/04/2003
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The complexation of oppositely charged colloidal objects is considered in this paper as a thermodynamic micellization process where each kind of object needs the others to micellize. This requirement gives rise to quantitatively different behaviors than the so-called mixed-micellization where each specie can micellize separately. A simple model of the grand potential for micelles is proposed to corroborate the predictions of this general approach.; Comment: 7 pages, 2 figures. Accepted for publication in Europhysics Letters

Theory of copolymer micellization

Duque, Daniel
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/06/2003
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We consider the micellization of block copolymers in solution, employing self consistent field theory with an additional constraint that permits the examination of intermediate structures. From the information for an isolated micelle (structure, binding energy, free energy) we describe how the global thermodynamics of these systems can be obtained, which can be used to build a realistic phase diagram; the role of translational entropy must be addressed in this regard.; Comment: 5 pages, 2 figures; more at http://www.sfu.ca/~dduque/mic.html

Three eras of micellization

Neu, J. C.; Cañizo Rincón, José Alfredo; Bonilla, L. L.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2002 ENG
Relevância na Pesquisa
279.48152%
Micellization is the precipitation of lipids from aqueous solution into aggregates with a broad distribution of aggregation number. Three eras of micellization are characterized in a simple kinetic model of Becker-Döring type. The model asigns the same constant energy to the (k-1) monomer-monomer bonds in a linear chain of k particles. The number of monomers decreases sharply and many clusters of small size are produced during the first era. During the second era, nuclei are increasing steadily in size until their distribution becomes a self-similar solution of the diffusion equation. Lastly, when the average size of the nuclei becomes comparable to its equilibrium value, a simple mean-field Fokker-Planck equation describes the final era until the equilibrium distribution is reached.

Kinetics of membrane micellization by the hydrophobic polyelectrolyte poly( 2-ethylacrylic acid)

Thomas, James L.; Devlin, Brian P.; Tirrell, David A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 12/01/1996
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Rates of pH-dependent micellization of multilamellar vesicles by the hydrophobic polyelectrolyte poly(2-ethylacrylic acid) (PEAA) have been measured turbidometrically. This polymer shows a strong pH-dependence in its affinity for phospholipid membranes, binding in increasing amounts as pH is lowered and ultimately solubilizing membranes to form mixed micelles (Tirrell, Takigawa and Seki (1985) Ann. N.Y. Acad. Sci. 446, 237). The rate of solubilization of dipalmitoylphosphatidylcholine (DPPC) vesicle suspensions by PEAA increases approximately linearly with reductions in pH below a threshold at pH 6.55. Interestingly, negatively-charged dipalmitoylphosphatidylglycerol membranes showed qualitatively similar behavior in the presence of PEAA, and incorporation of 10% or 20% dipalmitoylphosphatidic acid in DPPC membranes did not affect solubilization rates, demonstrating that membrane charge is not an important factor in determining micellization kinetics. Micellization of DPPC and dimyrstoylphosphatidylcholine membranes occurs most rapidly at their respective gel-liquid crystalline transition temperatures (Tm); the rate enhancement is correlated with a peak in the temperature-dependent binding of a fluorescently-modified PEAA in slightly alkaline solutions in which no micellization is observed. The lateral compressibility of the membrane...

Conductometric Studies on Terbium Soaps

Kishore,Kamal; Upadhyaya,S.K.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
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Conductivity measurements of solutions of terbium soaps in benzene-methanol show that these soaps behave as weak electrolytes in dilute solutions and Debye-HückelOnsager's equation is not applicable to these soap solutions. The thermodynamic results indicate that the micellization process is favoured over the dissociation process.

Investigation Into the Conductance, Micellization and Dissociation Behaviour of Terbium Caprylate and Caprate in 60/40 Benzene-methanol Mixture (v/v)

Kishore,Kamal; Upadhyaya,S. K.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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Conductance measurements were employed to determine the critical micellar concentration, CMC, limiting molar conductance at infinite dilution, degree of dissociation and dissociation constant of terbium caprylate and caprate in 60/40 benzene-methanol (v/v). The results have shown that these soaps behave as a weak electrolyte in dilute solutions and Debye-Hückel-Onsager’s equation is not applicable to these soap solutions. The thermodynamic parameters indicate that the micellization process is favoured over the dissociation process.