Showing papers on "Critical micelle concentration published in 1970"

Phase equilibria and their influence on the properties of emulsions

Abstract: Phase diagrams water-emulsifiers-oil have been investigated. Results show that not only the association of the three compounds into liquid crystalline phases has an effect on the properties of the emulsion but also that the association into micelles of the emulsifier in the oil phase influences both the type and the stability of the emulsion.

Prediction of the critical micelle concentration of mixtures of alkyltrimethylammonium salts

Abstract: The validity of Shinoda's equation for the critical micelle concentration (CMC) of a multicomponent soap mixture (1), ∑ C 1+K g m i μ i ′ exp (m i ω/kT) ∑ μ i ′ exp (m i ω/kT)=C 1+K g mix , has been tested for commercial samples of some long-chain alkyltrimethylammonium bromides. The samples were analyzed by gas-liquid chromatography and CMC's were determined at 25°C by conductivity and surface tension measurements. An average value for Kg of 0.65 was obtained from the variation of CMC with total gegenion concentration. Good agreement was found between experimental and theoretical CMC values for mixtures of alklytrimethylammonium bromides containing up to seven components.

Odd-even alternation in the chain length variation of micellar properties

Abstract: Lange andSchwuger have recently shown that in a homologous series of sodium alkyl sulphates, there is an alternation in theKrafft temperatures between alkyl chains containing odd and even numbered carbon atoms. They found no such alternation in the critical micelle concentrations, and concluded that the micelle core is liquid-like. It is shown here that alternations do exist in the free energies of micelle formation. This observation, in conjunction with some others, suggests that there is some long-range order inside a micelle. The magnitude of the alternation, however, is much less than those observed in heats of fusion of fatty acids or hydrocarbons. The existence of some ‘solidlike’ character in the micelle agrees with previous deductions that the entropy of the chains inside a micelle is likely to be less than that of hydrocarbon

Studies of Ester-Containing Surfactants. Preparation and Properties of Sodium Sulfoalkyl Alkanoates

Abstract: A series of sodium sulfoalkyl alkanoates, RCOO(CH2)jSO3Na, were prepared by means of sodium isethionate, propane sultone, and butane sultone with normal primary fatty acid composed of 10, 11, and 12 carbon atoms respectively. The effects of the position of the ester group on the Krafft point, the critical micelle concentration (CMC), the surface tention, and the other surface and colloidal properties of these surfactants were investigated. For a given number of carbon atoms, moving the ester group from the ionic head to a more central position in the hydrocarbon chain increased the CMC value and the calcium ion stalbility, and decreased the emulsion stability and the stability to hydrolysis. However, the wetting time was not strongly influenced by the position of the ester group in these compounds. The Krafft point of these surfactants decreased as the ester group was moved to a more central position.

The effect of added salt on the interaction between polymer and detergent in aqueous solution

Abstract: The effect of added NaCl on the interaction between polyvinyl acetate (PV Ac) and sodium dodecyl sulfate (SDS) has been studied in terms of surface tension, viscosity, and solubilization of Yellow-OB. The surface tension-concentration curve gives two transition points which show the concentration where the adsorption of SDS on PVAc first occurs and where SDS adsorbs totally. The critical micelle concentration (cmc) of SDS and the transition point of PVAC-SDS are lowered by the addition of NaCl. On increasing the concentration of NaCl in the PVAc-SDS solution, the reduced viscosity decreases and the solubilization ability increases. The effect of added NaCl on the PVAc-SDS complex is discussed in terms of electrostatic repulsion.

Biradical Spin-Labeled Micelles

Abstract: A biradical spin-label, N,N′-di-[4-(1-oxyl-2,2,6,6-tetramethylpiperidyl)] urea, has been used for studying the dynamic structure of a micelle, sodium dodecyl sulfate (SDS). Analysis of the ESR spectra of the label has shown that the biradical was incorporated in the micelle. The tumbling motion of the label in the micelle was not strongly inhibited, suggesting a dynamic character of the micelle structure. The exchange rate of the biradical between the micelle and the water phases was slower than 107sec−1. The partition coefficient expressed as the ratio of the concentration of the biradical in the micelle to that of the biradical in the water phase was approximately 6×105 in the SDS concentration lower than 2×10−2M. The biradicals form aggregate in the micelle, when they are present in excess in the solution.

Synthesis and properties of sulfated alkanolamides

Abstract: High purity alkanolamides were prepared by the sodium catalyzed reaction of methyl stearate, methyl palmitate and methyl laurate with ethanolamine, 2-hydroxypropylamine, 3-hydroxypropylamine and N-methyl N-hydroxyethylamine. The effect of structure on the surface active properties of the sulfation products was investigated. Stability studies showed that sulfated N-methyl N-hydroxyethylstearamide hydrolyzed rapidly by first order kinetics in acid or base. Sulfated hydroxyalkyl primary amides hydrolyzed slower in basic media following second order kinetics. Methyl groups attached to the N atom or to C in the short aliphatic chain improved solubility but had little effect on critical micelle concentration. The alkanolamides of palmitic and stearic acids were good detergents and lime soap dispersing agents.

Critical micelle concentration of some polyoxyethylated non-ionic surfactants and the effect of additives

Abstract: The effect of electrolytes on the concentration dependence of surface tension of some polyoxyethylated nonionic surfactants has been studied as a function of the electrolyte concentration and the lyotropic number of the ions. The lowering in the c.m.c. values in the case of electrolytes has been explained on the basis of salting out mechanism.

Determination of critical micelle concentration of surfactant by ultraviolet absorption spectra

Abstract: A method was investigated for determining the critical micelle concentration (CMC) by the shift of absorption maxima when an organic compound (I) with ultraviolet absorption was added to an aqueous solution of a surfactant. When I was added to the surfactant solution at higher concentrations (above the CMC), λmax of I approached the value inn-octane, since I was solubilized in the hydrocarbon atmosphere of the inner part of the surfactant micelle. At lower concentrations (below the CMC), however, I was present in the water phase and λmax approached the value in water. The curve of λmax vs. surfactant concentration declined from the high concentration values as the CMC was approached and at the CMC, the curve broke upward sharply. Then, it rose for some time and approached the value in water. N,N′-diethylaniline was used because it exhibited larger shifts of λmax. The standard amount used was 0.002 ml/3–10 ml of aqueous solution of the surfactant. The CMC values obtained agreed with those obtained by the electric conductivity method, dye adsorption method and light scattering method, for surfactants such as tetradecyldimethylbenzylammonium chloride, sodium dodecyl sulfate and polyoxyethylene cetyl ether.

The Properties of Aqueous Solutions of Sodium 2-Sulfoethyl Alkanoates and Sodium Alkyl β-Sulfopropionates

Abstract: A series of sodium 2-sulfoethyl alkanoates RCOO(CH2)2SO3Na was prepared from sodium isethionate and fatty acids containing 9, 11, 13, and 15 carbon atoms. The Krafft point, the critical micelle concentration (CMC), the surface tension, the emulsifying power, the wetting time, the resistance to acid hydrolysis, and the calcium-ion stability of this series of surfactants were examined, and the results were compared with those of the corresponding sodium alkyl β-sulfopropionates ROCO(CH2)2SO3Na, which have another structure of ester-linkage. The CMC values of sodium 2-sulfoethyl alkanoates almost coincide with those value of the sodium alkyl β-sulfopropionates with the same number of carbon atoms. However, the Krafft point and surface tension at the CMC of sodium 2-sulfoethyl alkanoates were lower than those of the sodium alkyl β-sulfopropionates with the same number of carbon atoms. Sodium 2-sulfoethyl alkanoates are more stable than sodium alkyl β-sulfopropionates in their resistance to hydrolysis and to t...

Salt effects on the critical micelle concentrations of nonionic surfactants

Abstract: Gordon has criticized the use of the mass-action model of micelle formation in the previous analysis of the effect of inorganic salts on the critical micelle concentrations (cmc) of nonionic surfactants and has suggested that the 2-phase model of micelle formation accounts reasonably well for the salt effects. This discussion is concerned with the nature of the assumptions involved in the application of the mass- action model and the limitations of the 2-phase model in describing the salt effects. Although the 2-phase and the mass-action models give similar results for the salt effects on the cmc's of octyl glucoside and alkyl betaines, the salt effects on polyoxyethylene-type nonionic surfactants are in poor accord with the 2-phase model of micelle formation, various arguments against which have been summarized elsewhere. The mass-action model, as used earlier, appears to be better. (15 refs.)

Fluorescence and differential ultraviolet spectroscopic studies of micellar solutions of sodium phenylundecanoate

Abstract: The sodium phenylundecanoate molecule with the polar functional group and the aromatic group at opposite ends of an alkyl chain provides a model compound which allows the use of differential ultraviolet spectroscopy and fluorescence spectroscopy to investigate the interior of the micelle. The spectral analysis indicates that the micellar unit has a liquid core of phenyl rings. The absorption spectra show no evidence for association of the phenyl group below the critical micelle concentration (c.m.c.). However, evidence for the formation of short-lived excited complexes below and above the c.m.c. is found in the fluorescence spectra.

The Effect of a Non‐ionic Detergent on Some Plant Cells

Abstract: The effects of a non-ionic detergent Triton × 100, on protoplasmic streaming in some plant cells, on plasmolysis, and on leakage of solutes from beet cells were investigated The results of the different tests showed some features in common: (1) There is a critical range between 0007 and 001 % v/v (2) Above this concentration of the surfactant, that is at a concentration close to 001 %, the effect is manifested in the following ways Plasmolysis with sucrose is anomalous or impossible Protoplasmic streaming ceases within a short time Definite leakage of ions and sugars starts from beet tissues (3) At concentrations lower than 001 to 0007 % there is enhanced retention of solutes in beet disks — It is thought that the critical micelle concentration is of paramount importance The micelle effect may consist in solubilizing or in forming mixed micelles or a complex with the globular lipoprotein units of the outermost plasma layer, the plasmalemma The effect of the lower Triton concentrations is discussed

Preparation and properties of sodium alkyl β-sulfopropionates

Abstract: A series of sodium alkyl β-sulfopropionates containing 11 to 17 carbon atoms was prepared from β-bromopropionic acid, sodium sulfite and even-numbered straight chain alcohols of 8 to 14 carbon atoms. The Krafft point, critical micelle concentration (cmc), emulsifying power, calcium ion stability and resistance to acid hydrolysis were determined. Sodium alkyl β-sulfopropionates, in which the ester linkage (hydrophilic group) is moved toward a more central position in the alkyl chain, have higher cmc values and lower Krafft points than the corresponding sodium alkyl sulfoacetates. The sodium alkyl β-sulfopropionates were less stable toward hydrolysis than the sodium alkyl sulfoacetates because the adjacent sulfo group in the sulfoacetates protects the ester linkage through steric hindrance. The emulsifying power increases, but the calcium ion stability decreases, with increasing alkyl chain length for a series of sodium alkyl β-sulfopropionates.

ζ-Potentials of Natural and Synthetic Fibers in SDS Solutions and the Viscosity of SDS Solutions above the Critical Micelle Concentration

Abstract: In order to investigate the adsorption behavior of an anionic surfactant on fibers, the ζ-potentials of natural and synthetic fibers in aqueous solutions of sodium dodecyl sulfate (SDS), mainly above the critical micelle concentration (CMC), were measured. Further, the change in the structure of the SDS micelle in aqueous solutions was studied by means of the viscosity method. At first the reduced viscosity for the SDS micelle, ηspm/cm (cm: the micellar concentration), increased rapidly with the cm as long as the cm was small; thereafter, after a break, it approximated the saturated values as a whole. The results calculated from the experimental data using Jones and Dole’s equation showed two distinct breaks. The first break corresponded to the 1st CMC, and the second, nearly to the break in the ηspm/cm vs. cm curve. In addition, the intrinsic viscosity for the SDS micelle, [η]M, and the effective specific volume, V, were obtained. From these results, it can be assumed that the structure of the SDS micell...

Absorption and fluorescence of a nonionic detergent in aqueous solution

Abstract: The absorption and fluorescence spectra of a detergent, polyoxyethylene octylphenyl ether, were measured in water at different concentrations. The absorption spectra had a peak at 275 mμ and a shoulder at 281 mμ. The spectra were independent of concentration below the critical micelle concentration, but the molar extinction coefficients of the peak and the shoulder increased with concentration above the critical micelle concentration. The critical micelle concentration value derived from the absorption data was in good agreement with those obtained by other methods. The fluorescence spectra of the detergent in water were independent of concentration in dilute solutions, if the intensities of the spectra were normalized at the peak at 302 mμ. At higher concentrations, a weak excimer band appeared at 345 mμ, whose intensity increased with concentration. The excimer band manifested itself at a concentration slightly lower than the critical micelle concentration. The main band decreased and the excimer band increased, as the temperature was raised. An excimer band was observed in the same region of the spectra for the pure detergent, either in the solid or liquid state. The equilibrium solid spectra exhibited a very strong excimer emission. It was concluded that the excimers were formed within micelles in the case of aqueous solutions.

ζ-Potentials of Synthetic Fibers in Aqueous Solutions of Sodium Alkyl Sulfates and Viscosities of Their Solutions

Abstract: In order to study the surface-adsorption behavior of anionic surfactants on fibers, the ζ-potentials of some synthetic fibers in aqueous solutions of sodium alkyl sulfates and their mixtures mainly above the critical micelle concentration (CMC), were measured. Further, the viscosities of aqueous solutions of pure surfactants were determined. Consequently, it can be presumed, on the basis of the viscosity data, that the structure of the micelles of these agents varies at the break of the ηspm⁄cm vs. cm curve. The ζ-potentials (negative) of fibers in aqueous solutions of the agents rapidly changed with an increase in the agent concentrations, but it remained nearly constant above the CMC. At much higher concentrations, the ζ values gradually changed; thereafter, passing a break or a minimum, they became approximately constant again. The concentration at the break or the minimum observed nearly corresponded to that at the break of the ηspm⁄cm vs. cm curve. It may, therefore, be suggested that the change in ζ...

Salt effects on the critical micelle concentrations of nonionic amphiphiles

Abstract: Added inorganic electrolyte lowers the critical micelle concentration (cmc) of nonionic as well as ionic amphiphiles. The usual account of the latter case, in terms of the shielding of repulsive interactions between charged head groups cannot be applied to the former. The purpose of this study is to point out that Mukerjee's expression in fact corresponds to no common model of micellization, to present correct derivations for the mass-law and pseudophase models and to compare the results with experiment. The pseudophase model of micelle formation, although serious objections to it have been presented, accounts reasonably well (in conjunction with the McDevit-Long theory) for the effects of salt on the cmc of nonionic amphiphiles, while the mass-law model does not.

Determination of Critical Micelle Concentration of copper soaps in non-aqueous solvents

Abstract: The critical micelle concentration (C.M.C.) for copper soaps has been determined from studies of density, viscosity and surface tension of non-aqueous solutions of copper soaps. The C.M.C. values depend on the nature of the solvent and the values are higher in alcohols than in hydrocarbons. The plots of density, viscosity, specific viscosity and surface tension against the soap concentration are characterised by an intersection of two straight lines at a definite soap concentration which corresponds to the C.M.C. of the soaps.

Some Physicochemical Properties of a Series of Sodium N-Alkyloyl Sarcosinates

Abstract: Physicochemical properties, such as foaming power, solubilizing power, suface tension and others, of a series of sodium N-alkyloyl sarcosinates (abbreviated as CnCO sarcosinates) with n from 9 to 17 have been measured in relation to their alkyloyl chain length. These properties are highly dependent on the alkyloyl chain length as expected. The foaming power at 25°C increases at first with increasing chain length until n reaches to 15, and then decreases rapidly owing to the low solubility in water. The solubilizing power for an oil soluble dye, Yellow OB, increases with increasing chain length. The surface tension above the critical micelle concentration is approximately 35 dyne/cm irrespectively of the chain length. The solubility in water becomes low when n exceeds 15. The properties of the mixtures of CnCO sarcosinates with different alkyloyl chain-length have been also examined. The effects of soap and water hardness on the foaming power of C11CO sarcosinate were also reported.

Interaction of detergents with transfusion gelatin

Abstract: Binding of sodium dodecyl and octyl sulphate to transfusion gelatin has been studied at pH 7.7 by equilibrium dialysis. At lower detergent concentration the binding is statistical, whereas at higher concentrations the binding increases apparently without limit. This may be explained by assuming unfolding of the protein molecule with formation of detergent micelles around the binding sites.