Studies of Aqueous Sodium Dodecyl Sulfate Solutions by Activity Measurements

Sasaki, Tetsuo; Hattori, Michihiro; Sasaki, Jun; Nukina, Kenji

doi:10.1246/bcsj.48.1397

Cited by 214 publications

(176 citation statements)

References 44 publications

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“…An approximate value of R may be obtained from eq 10 because mass action theory predicts that K 4 ≈ 1 -R in the limit of large aggregation numbers. 40,41 This interpretation obviously requires an implicit assumption that R be constant. Column 8 of Table 2 gives these approximate values.…”

Section: Discussionmentioning

confidence: 99%

Aggregation Number-Based Degrees of Counterion Dissociation in Sodium n-Alkyl Sulfate Micelles

2005

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Values of the degree of counterion dissociation, R, for sodium n-alkyl sulfate micelles, denoted by SN c S, where N c is the number of carbon atoms in the alkyl chain, are defined by asserting that the aggregation number, N, is dependent only on the concentration, C aq , of counterions in the aqueous pseudophase. By using different combinations of surfactant and added salt concentrations to yield the same value of N, R can be determined, independent of the experimental method. Electron paramagnetic resonance measurements of the hyperfine spacings of two nitroxide spin probes, 16-and 5-doxylstearic acid methyl ester (16DSE and 5DSE, respectively), are employed to determine whether micelles from two samples have the same value of N to high precision. The EPR spectra are different for the two spin probes, but the values of R are the same, within experimental error, as they must be. In agreement with recent work on S12S and with prevailing thought in the literature, values of R are constant as a function of N. This implies that the value of R is constant whether the surfactant or added electrolyte concentrations are varied. Interestingly, R varies with chain length as follows: However, the theory also predicts that, for a given value of N c , R decreases as N increases. Moreover, this decrease is predicted to be different if N is increased by adding salt or by increasing the surfactant concentration. A modification to the theory in which dissociated counterions contribute to the ionic strength while added co-ions (Cl -) do not, brings theory and experiment into closer accord. Assuming R to be constant versus N permits a direct application of the aggregation number-based definition of R using time-resolved fluorescence quenching to measure values of N as well as other experimental parameters that vary monotonically with N, such as the microviscosity measured with spin probes and the quenching rate constant. For S13S micelles at 40°C, R ) 0.20 ( 0.02 is derived from N; R ) 0.21 ( 0.02 from the microvisicosity, and R ) 0.21 ( 0.02 from the quenching rate constants, in agreement with the hyperfine spacing results. The aggregation numbers for S13S are well described by the power law N ) N°(C aq /cmc 0 ) γ , where cmc 0 is the critical micelle concentration in the absence of added salt, N°) 67, and γ ) 0.26.

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Section: Discussionmentioning

confidence: 99%

Aggregation Number-Based Degrees of Counterion Dissociation in Sodium n-Alkyl Sulfate Micelles

2005

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“…MIm]Cl 0.4 [2] 0.45 [2] 0.27 A C H T U N G T R E N N U N G [C 8 Py]Cl 274 [2] 292 NaA C H T U N G T R E N N U N G [C 8 SO 4 ] 134 [35] 143 NaA C H T U N G T R E N N U N G [C 10 SO 4 ] 3 0 [35] 30 NaA C H T U N G T R E N N U N G [C 12 SO 4 ] 7.6 [36] 7.0 NaA C H T U N G T R E N N U N G [C 14 SO 4 ] 2.00 [35] 1.6…”

Section: 6mentioning

confidence: 99%

Predicting the Critical Micelle Concentrations of Aqueous Solutions of Ionic Liquids and Other Ionic Surfactants

Preiss

Jungnickel

Thöming

et al. 2009

Chemistry A European J

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Some ionic liquids (ILs) are structurally analogous to surfactants, especially those that consist of a combination of organic and inorganic ions. The critical micelle concentration (CMC) is a basic parameter of surface chemistry and colloid science. A significant amount of research has already been carried out to determine the CMCs of ILs. However, because of the many varied cation/anion combinations, it is a daunting task to measure the CMCs of all possible ILs. Herein we suggest a general rule for predicting the CMCs of ionic surfactants in water based on data from COSMO-RS calculations. In accordance with the Stauff-Klevens rule, the molecular volume (V(m)) is sufficient to describe similar homologous series of cationic surfactants such as imidazolium- and ammonium-based ionic liquids with varying side-chain lengths. However, to also include anionic surfactants like Na[C(n)SO(4)] in a more general correlation, V(m) has to be exchanged by the cubed molecular radius (r3(m)) and the molecular surface has to be used as an additional descriptor. Furthermore, to describe double amphiphilic compounds like [C(4)MIm][C(8)SO(4)], the enthalpies of mixtures calculated by COSMO-RS have to be taken into account. The resulting equation had allowed us to predict the CMCs of all of the 36 tested surfactants with an error similar to or smaller than the usual experimental errors (18 different cations, 10 different anions: root mean squared error (rmse)=0.191 logarithmic units; R(2)=0.994). We discuss the factors governing micelle formation on the basis of our calculations and show that the structure of our equation can be related to Gibbs' theory of crystallization.

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“…Input parameters were the pure water value, e m e(0) 78.37, [20] for the static permittivity of the suspending medium and the experimental conductivity, k (Table 1), for k m . Neglecting minor contributions from free anions and concentration changes, the diffusion coefficient of the Na ion at infinite dilution, 1.334 Â 10 À9 m 2 s À1 , [10] was used for D. The degree of couterion attachment, b 0.73, was taken from Sasaki et al [23] Simultaneously, the theory of Pauly and Schwan [24] (P&S) was tested. In this approach, which yielded comparable results for C n TAX solutions, [8,7] micelles are modeled as a hydrophobic core (radius R c , permittivity e c 2, conductivity k c 0) surrounded by a layer of thickness d (permittivity e s , conductivity k s ) containing the headgroups, adsorbed counterions and bound water that is embedded in a medium of permittivity e m 78.37 and conductivity k m k. Note, that this theory only accounts for the interfacial polarization but not for the relaxation of the counterion cloud, thus only allows to fit S 2 and t 2 .…”

mentioning

confidence: 99%

Micelle and Solvent Relaxation in Aqueous Sodium Dodecylsulfate Solutions

et al. 2003

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Dielectric spectra have been measured for aqueous sodium dodecylsulfate (SDS) solutions up to 0.1 mol L-1 at 25 degrees C over the frequency range 0.005 < or = nu GHz-1 < or = 89. The spectra exhibit two relaxation processes at approximately 0.03 GHz and 0.2 GHz associated with the presence of micelles in addition to the dominant solvent relaxation process at approximately 18 GHz and a small contribution at approximately 1.8 GHz due to H2O molecules hydrating the micelles. Detailed analysis reveals that the micelles bind 20 water molecules per SDS unit, but not as strongly as trimethylalkylammonium halide surfactants do. The relaxation times and amplitudes of both micelle relaxation processes can be simultaneously analysed with the theory of Grosse, yielding the effective volume of a SDS unit in the micelle and the lateral diffusion coefficient of the bound counterions. The findings of this investigation fully corroborate recent molecular dynamics simulations on structure and dynamics of SDS micelles.

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Studies of Aqueous Sodium Dodecyl Sulfate Solutions by Activity Measurements

Cited by 214 publications

References 44 publications

Aggregation Number-Based Degrees of Counterion Dissociation in Sodium n-Alkyl Sulfate Micelles

Aggregation Number-Based Degrees of Counterion Dissociation in Sodium n-Alkyl Sulfate Micelles

Predicting the Critical Micelle Concentrations of Aqueous Solutions of Ionic Liquids and Other Ionic Surfactants

Micelle and Solvent Relaxation in Aqueous Sodium Dodecylsulfate Solutions

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