Micellization of sodium dodecyl sulfate and polyoxyethylene dodecyl ethers in solution

The effect of polyoxyethylene type nonionic surfactants (C₁₂E _n n = 3, 4, 5, 6, 7 and 8) on the aqueous solution of sodium dodecyl sulfate (SDS) in absence and presence of NaCl was examined using small-angle neutron scattering (SANS), dynamic light scattering (DLS), and viscosity measurements. Upon addition of C₁₂E _n , micellar size of SDS was found to increase significantly, and such micellar elongation was further enhanced in the presence of NaCl. Micellar growth is most significant in presence of shorter moieties of C₁₂E _n (e.g., n = 3, 4) as compared to higher ethereal oxygen content. The results of structural investigations with SANS and DLS to confirm this assumption are reported. The cloud point of C₁₂E _n has increased upon addition of SDS and decrease with NaCl, and a typical behavior is observed when both SDS and NaCl were present.     

Interaction between casein and sodium dodecyl sulfate

The interaction of the anionic surfactant sodium dodecyl sulfate (SDS) with 2.0 mg/ml casein was first investigated using isothermal titration calorimetry (ITC), dynamic light scattering (DLS), and fluorescence spectra. ITC results show that individual SDS molecules first bind to casein micelles by the hydrophobic interaction. The micelle-like SDS aggregate is formed on the casein chains when SDS concentration reaches the critical aggregation concentration (c1), which is far below the critical micellar concentration (cmc) of SDS in the absence of casein. With the further increase of SDS concentration to the saturate binding concentration c2, SDS molecules no longer bind to the casein chains, and free SDS micelles coexist with casein micelles bound with SDS aggregates in the system. DLS results show that the addition of SDS leads to an increase in the hydrodynamic radius of casein micelles with bound surfactant at SDS concentration higher than 4 mM, and also an increase in the casein monomer molecule (or submicelles) at SDS concentration higher than 10 mM. Fluorometric results suggest the addition of SDS leads to some changes in the binding process of hydrophobic probes to casein micelles.     

Interaction between polyacrylamide and sodium dodecyl sulfate

Summary Some preliminar results about the interaction between -SDS and polyacrylamide reveal that without added salts, the two compounds mixt by keeping their own properties while, in salt presence, there is probably complex formation.

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Resumé Quelques résultats préliminaires de l'étude des interactions entre SDS et polyacrylamide montrent un comportement diffèrent en presence et en absence de sels; dans ce dernier cas seulement on peut s'attendre à la formation de complexes.

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With 3 figures     

Hair protein removal by sodium dodecyl sulfate

The effect of sodium dodecyl sulfate (SDS) on protein loss was studied. Three kinds of human hair were tested by rubbing or immersion in water or immersion in SDS solution, at 25, 40 and 70 degrees C. Under friction, hair treated with SDS solution loses seven times more protein than in water, while by immersion, protein loss is roughly two times higher in SDS than in water. Protein loss increases at higher temperatures. Estimated activation energy values for protein loss by immersion are 69+/-22 kJ mol(-1) for blended brown hair; 40+/-12 kJ mol(-1) for blond hair (tip-end region) and 61+/-4 kJ mol(-1) for blond hair (root-end region) for samples treated in water, while 53+/-8, 7+/-5 and 32+/-8 kJ mol(-1) were the corresponding activation energy values for samples treated in 5% SDS solution. These values indicate that protein loss is mainly a diffusion-controlled process. The more damaged the hair, the lower the activation energy and the higher the protein loss. From these data, it can be estimated that daily care shampooing at room temperature will cause opacity and combing difficulties in 1 year and split ends after 3 years by removal of all cuticle layers.     

Aggregation of sodium dodecyl sulfate in aqueous sodium chloride solutions

Summary Aqueous solutions of sodium dodecyl sulfate with added sodium chloride (0–0.3 mol kg^–1) were studied at 298.2 K in order to calculate the molar standard free energy of micelle formationG _m . The following properties were measured: (i) aggregation number by membrane osmometry, (ii) counter-ion binding and sodium ion activities by electromotive force, (iii) critical micelle concentration by electromotive force and fluorescence spectrophotometry. The results indicate thatG _m . is independent of the NaCl concentration.     

Location of ethanol in sodium dodecyl sulfate aggregates

The hexagonal liquid crystalline phase of SDS (Sodium dode-cyl sulfate)/H2O system changes into lamellar liquid crystal and the effective length of surfactant molecule d0/2 in the lamellar liquid crystal decreases with the addition of ethanol. The micellar aggregation number N of SDS decreases and the micellar diffusion coefficient increases with the added ethanol. Under a constant concentration of SDS, the molecule number ratio of ethanol to SDS in the micelle increases with the concentration of ethanol and even exceeds 10 when ethanol concentration is 1. 085 mol/L. All these results show that ethanol, even though a short chain alcohol and soluble in water, can partly exist in the interphase of the amphiphilic aggregates showing some properties of co-surfactant.     

Thermodynamics of protein denaturation by sodium dodecyl sulfate

The anionic surfactant sodium n-dodecyl sulfate (SDS) plays a variety of roles with regard to protein conformation, depending on its concentration. SDS at low concentrations mostly induces the compaction of protein (folding). Examples of this include: the molten globule state of acid-unfolded cytochrome c, associated with enhancement of the exothermic enthalpy values of isothermal titration calorimetry and a reversible profile by differential scanning calorimetry; the enzyme activation and compaction of Aspergillus niger catalase, and relationship of calorimetric enthalpy (ΔH_cal) to van’t Hoff enthalpy (ΔH_VH), which proves the existence of intermolecular and intramolecular interaction during enzyme activation by SDS; the production of a new energetic domain for human apotransferrin and folded state for histone H1 by SDS. SDS at moderate concentrations below the critical micelle concentration (cmc) is a potent denaturant for protein in solution. Protein denaturation is a key method in thermodynamics and binding site analysis and can be used to enhance our understanding of the protein structure-function relationship. The interaction between protein and surfactant, such as SDS, at the cmc level is a complicated interaction, thermodynamically, that should bring about enthalpy correction through micellar dissociation and micelle dilution.     

Miscibility of sodium dodecyl sulfate and sodium decyl sulfate in the adsorbed film and micelle

The interfacial tension of the aqueous solution of sodium dodecyl sulfate (SDS) and sodium decyl sulfate (SDeS) mixture against hexane was measured as a function of the total molality and composition of the surfactant mixture at 298.15 K under atmospheric pressure. The compositions of adsorbed film and micelle were evaluated numerically by applying the thermodynamic relations to the experimental results. These results were shown in the form of the phase diagrams of adsorption and micelle formation and compared with those of the aqueous solution of sodium perfluorooctanoate (SPFO) and SDeS mixture. It was found that the diagrams of SDS and SDeS system have swollen cigar shapes and are quite different from those of SPFO and SDeS system which show non-ideal mixing both in the adsorbed film and micelle. This finding was attributed to the fact that the interaction between fluorocarbon and hydrocarbon chains is weaker than that between hydrocarbon chains.     

Nonequilibrium electrodialysis of aqueous solution of sodium dodecyl sulfate

Summary Special dialysis apparatus was constructed which enabled to trace a short time nonequilibrium dialysis by the continuous measurement of electric resistance of dialyzing solution. The apparatus is particularly suited for the study of the formation of micelles in surfactant solution. The dialysis curves were constructed by plotting the change of electric resistance against dialysis time. The diagrams consisted of a nearly straight line at low concentration and two nearly straight lines above a certain concentration, from which CMC was sharply determined and the constancy of a single ion concentration above CMC was also demonstrated.

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Zusammenfassung Es wurde ein neuartiger Dialyseapparat entwickelt, der es ermöglicht, die Nichtgleichgewichtsdialyse über kurze Zeiten auszuführen und den Lösungszustand der grenzflächenaktiven Substanzen, die die Mizellen enthalten, genauer zu bestimmen. Die gemessenen Dialysekurven, die die Abhängigkeit des elektrischen Widerstands von der Zeit geben, stellen unterhalb der CMC eine fast gerade Linie dar, während oberhalb der CMC jede Kurve aus zwei geraden Stücken mit einem Knick im Schnittpunkt besteht. Hieraus konnten wir die CMC genau bestimmen und die Konstanz der Zwischenmizellkonzentration feststellen.

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Authors wish to express their thanks to Assistant ProfessorS. Okazaki of Sophia University for her help in this research.     

Effect of sodium dodecyl sulfate on lipase ofCandida lipolytica

The effects of sodium dodecyl sulfate on extracellular lipase produced byCandida lipolytica have been studied. The microorganism was grown in culture medium containing different sodium dodecyl sulfate concentrations added to the culture at different intervals of growth. The extracellular lipase activity was not detected when the treated culture supernatants were directly tested in Yeast Mold Agar-Triolein-Rhodamine plates, regardless of surfactant addition time and concentrations. However, after ammonium sulfate precipitation and dialysis, the extracellular lipase activity could be recovered. Therefore, the surfactant, under the experimental conditions used here, does not seem to be able to inhibit lipase production, but it does inhibit the enzyme activity because of its presence in the mixture of the reaction.     

Ion flotation of rare-earth metals with sodium dodecyl sulfate

Ion flotation of rare-earth metals with sodium dodecyl sulfate and the effect of chloride ions on this process were studied. Values of the distribution coefficients were obtained.     

Photooxidative decomposition of sodium dodecyl sulfate in aqueous solutions

Kinetic features and the mechanism of photooxidative decomposition of sodium dodecyl sulfate in an aqueous solution under the action of pulsed short-wavelength UV light with a continuous spectrum upon introduction of hydrogen peroxide was studied.     

Interaction of sodium dodecyl sulfate with methacrylate-PEG comb copolymers

A series of sodium methacrylate and poly(ethylene glycol) (PEG) comb copolymers (MAA/PEG) with approximate PEG chain lengths of 7, 11, and 22 ethylene oxide units were synthesized by free radical polymerization. Their weight-average molecular mass was found to be approximately 66 000. A commercial sample of a PEG comb polymer with an acrylic backbone was also used in the studies (Sokalan HP 80). The interaction of the MAA/PEG comb polymers and pure sodium methacrylate (SPMA) with sodium dodecyl sulfate (SDS) was studied by ESR spectroscopy using 5-doxyl stearic acid (5-DSA) spin probe and by conductivity measurements. Surfactant aggregation in water occurred at SDS concentrations lower than the surfactant critical micelle concentration (cmc) and depended on the polymer concentration. The observations have been attributed to changes in the effective ionic strength of the systems due to the polymer itself, and it has been concluded that there is no interaction between the MAA/PEG comb copolymers or SPMA and SDS. This has been confirmed by the fact that the decrease in surfactant aggregation concentration is similar in magnitude to the decrease observed on adding NaCl when counterion ion condensation effects are taken into account. It is apparent that the electrostatic repulsions between the surfactant molecules and the methacrylate backbone of the MAA/PEG comb copolymers inhibit association of SDS with the PEG side chains.     

Diffusion of sodium dodecyl sulfate micelles in agarose gels

The gradient diffusion of ionic sodium dodecyl sulfate micelles in agarose gel was investigated at moderate concentrations above the CMC. Of particular interest were the effects of micelle, gel, and sodium chloride concentration on the micelle diffusivity. Holographic interferometry was used to measure the gradient diffusion coefficient at three sodium chloride concentrations (0, 0.03, 0.10 M), three gel concentrations (0, 1, 2 wt%), and several surfactant concentrations. Time-resolved fluorescence quenching was used to measure aggregation numbers both in solution and gel. The micelle diffusivity increased linearly with surfactant concentration at the two larger sodium chloride concentrations and all gel concentrations. In general, the strength of this effect increased with decreasing sodium chloride concentration and increased with gel concentration. This behavior is evidence of decreasing micelle-micelle electrostatic interactions with increasing sodium chloride concentrations, and increasing excluded volume effects and hydrodynamic screening with increasing gel concentration, respectively. The only exception was at 0.1M sodium chloride and 2 wt% agarose, which showed a slight reduction in the slope compared to 1 wt% agarose. It was found that the concentration effect is quite strong for charged solutes: at a NaCl concentration of 0.03 M in a 2% agarose gel, in a solution with 3% SDS micelles by volume, the micelle diffusion coefficient is doubled relative to its value in the same gel at infinite dilution. The extrapolated, infinite-dilution diffusion coefficients and the rate at which the micelle diffusivity increased with surfactant concentration were compared with predictions of previously published theories in which the micelles are treated as charged, colloidal spheres and the gel as a Brinkman medium. The experimental data and theoretical predictions were in good agreement.     

Micellar phases based on sodium dodecyl sulfate for preconcentration

Features of phase formation from solutions of sodium dodecyl sulfate on cooling were examined. The effect of electrolyte and phenol additions on the parameters of phase formation and distribution of model substrates was examined. Conditions were found for albumin preconcentration with phases in the system sodium dodecyl sulfate-phenol-NaCl.     

Complexation between sodium dodecyl sulfate and amphoteric polyurethane nanoparticles

The complexation between negatively charged sodium dodecyl sulfate (SDS) and positively charged amphoteric polyurethane (APU) self-assembled nanoparticles (NPs) containing nonionic hydrophobic segments is studied by dynamic light scattering, pyrene fluorescent probing, zeta-potential, and transmission electron microscopy (TEM) in the present paper. With increasing the mol ratio of SDS to the positive charges on the surface of APU NPs, the aqueous solution of APU NPs presents precipitation at pH 2, around stoichiometric SDS concentration, and then the precipitate dissociates with excess SDS to form more stable nanoparticles of ionomer complexes. Three stages of the complexation process are clearly shown by the pyrene I1/I3 variation of the complex systems, which only depends on the ratio of SDS/APU, and demonstrate that the process is dominated by electrostatic attraction and hydrophobic aggregation.     

芘荧光探针法研究海藻酸钠与SDS的作用

采用芘荧光法研究了海藻酸钠(NaAlg)与十二烷基硫酸钠(SDS)在不同pH水溶液中的相互作用.以芘单体的荧光光谱第一峰与第三峰的荧光强度之比(I1/I3)及激基缔合物与单体荧光强度之比(IE/IM)来探测芘分子所处环境的极性.结果表明:NaAlg水溶液随pH值降低,出现了聚合物的疏水微区;pH从7降到5,NaAlg类似简单盐,对SDS的临界胶束浓度(CMC)有明显的影响;在pH 3时,海藻酸主链上有足够的疏水片段,使得SDS与海藻酸通过疏水性作用而聚集.NaCl对NaAlg /SDS体系的影响亦较明显.     

Sorption of sodium dodecyl sulfate by highly basic anion-exchange resins

The interaction in the system of sodium dodecyl sulfate (SDS) solution and AB-17 highly basic anion-exchange resins in OH⁻ and Cl⁻ forms were considered, and the distribution coefficients (K _d) of the substance in the resin-solution ion exchange system were calculated. It was found that K _d decreases with increasing concentration of the initial solution, reaching a maximum value at the critical micelle concentration (CMC) of SDS. The effective diffusion coefficients of the surfactant in the anion-exchange resin phase were calculated; based on the IR spectroscopy data, the mechanism of SDS absorption was proposed.