Showing papers on "Critical micelle concentration published in 1969"
TL;DR: Bile salts behave as nonionic detergents with dyes of opposite charge and allow the first break point in a plot of the λ-max shift vs. log concentration of bile salt to be taken as an estimate of the CMC, showing that the micelles are highly charged and bind little or no counterions in water.
251 citations
01 Sep 1969
TL;DR: Adsorption of sodium dodecylbenzene sulfonate emulsifier has been measured on polystyrene (PS) and poly(methyl methacrylate) (PMMA) latex particles as mentioned in this paper.
Abstract: Adsorption of sodium dodecylbenzene sulfonate emulsifier has been measured on polystyrene (PS) and poly(methyl methacrylate) (PMMA) latex particles. Surface tension titration curves permit calculation of adsorption at various concentrations of emulsifier. The data fit a Langmuir isotherm equation and indicate a limiting area A 0 of 35 A 2 for an emulsifier molecule. The A 0 does not depend on the nature of the polymer. But at the critical micelle concentration the area A m per adsorbed emulsifier molecule is 53 A 2 on PS and 131 A 2 on PMMA in .005 N salt. For salt-free PS latex A m is 62 A 2 . Thus A 0 appears to be a characteristic of the emulsifier. But A m depends markedly on the nature of the polymer surface. Hence measurements of A m may be used to characterize a latex particle surface. PMMA grown on a PS seed latex appears to cover the PS surface completely, from an adsorption standpoint, with a PMMA shell as thin as 25 A.
75 citations
TL;DR: It is concluded that one of the effects of the bile acid is to remove the fatty acids from the interface, thus allowing the hydrolysis of lipase to continue at a constant rate.
70 citations
TL;DR: The enthalpy of micellization of sodium n -dodecylsulphate in aqueous and in 0.023 mol dm −3 sodium chloride solution, as a function of concentration of surfactant and of temperature has been measured using a Beckman 190B microcalorimeter as mentioned in this paper.
59 citations
TL;DR: Comparison with work by other authors on taurodeoxy-cholate-cholesterol micelles suggests that more than 25 molecules of either dihydroxy or trihydroxy bile salts are needed to transport each molecule of cholesterol through an aqueous solution in the absence of other amphipathic molecules.
58 citations
52 citations
43 citations
TL;DR: Analysis of the colligative properties of dilute aqueous solutions of non-ionic surface-active agents has enabled the concentration of monomer to be determined as a function of the total solute concentration.
Abstract: In dilute aqueous solution surface-active molecules aggregate to form micelles. This process has been described by a multiple equilibrium model which considers changes in the distribution of micelle aggregation numbers with concentration. Analysis of the colligative properties of dilute aqueous solutions of non-ionic surface-active agents has enabled the concentration of monomer to be determined as a function of the total solute concentration. The validity of the treatment has been confirmed by showing that these monomer concentrations are in good agreement with those deduced from nuclear magnetic resonance experiments, which do not depend on the assumptions employed in the thermodynamic method. Only one colligative property need be determined as a function of concentration in order to describe adequately the average aggregation numbers and free energies of micelle formation.
39 citations
01 Jan 1969
TL;DR: The effect of methanol on the micellar behaviour of aqueous solutions of sodium dodecyl sulphate has been studied by light scattering measurements as discussed by the authors. But the effect of micelle formation was not investigated.
Abstract: The effect of addition of methanol on the micellar behaviour of aqueous solutions of sodium dodecyl sulphate has been studied by light scattering measurements At low alcohol concentration there is a small decrease in the critical micelle concentration but no change in micellar weight With increasing alcohol concentration the critical micelle concentration increases and the micellar weight decreases, and at about a mole fraction of alcohol of 025 there is no evidence of micelle formation Interpretation of the behaviour requires a knowledge as yet unknown of the part played by the changes in solvent structure and dielectric constant, and by the penetration of additive into the micelles
38 citations
TL;DR: The CMC of cetomacrogol 1000 was practically unaffected by the addition of salt and the extent of interfacial tension reduction with respect to salt concentration was small when compared to corresponding systems containing ionic surfactants.
37 citations
01 Aug 1969
TL;DR: In this paper, the synthesis of surface-active pyridinium halides containing a nonionic polar group in the 4-position of the pyrinium ring is described.
Abstract: The synthesis of some new surface-active pyridinium halides containing a nonionic polar group in the 4-position of the pyridinium ring is described. Conductivity measurements have been made to determine the c.m.c. of the amphipathic electrolytes from 5° to 60° C at 5° intervals. Changing the anion from bromide to chloride causes an increase in the temperature at which the minimum c.m.c. occurs. The effect of the nonionic polar group on the c.m.c. is discussed. For each salt a series of polynomials has been fitted to the c.m.c.-temperature data with the use of a Stantec Zebra Computer. These polynomials have been used to give the conventional thermodynamic parameters of micelle formation.
TL;DR: In this paper, the interaction of sodium dodecyl sulfate (NaDS) with styrene-butadiene latexes was investigated by application of the recently developed spin-probe technique.
Abstract: The interaction of sodium dodecyl sulfate (NaDS) with styrene—butadiene latexes was investigated by application of the recently developed spin-probe technique. It is possible by this method to detect the presence of micelles in a latex reasonably quantitatively. The effective surface area occupied per molecule of soap was calculated to be 53 A2. Differences in purity can readily be detected for several NaDS samples. The less pure samples show a lower critical micelle concentration (CMC) and a significantly more ordered micelle structure. The addition of hexane to NaDS solutions above the CMC leads to a greater immobilization of the spin probe. This is interpreted as reflecting a tighter packing of the soap molecules. The addition of ethanol, acetic acid, and acrylic acid leads to a looser association of the probe with the micelles. The micelles catalyze the decomposition of the nitroxide probe in the presence of organic acids. The aggregation of sodium deoxycholate was also conveniently followed by the spin-probe method.
01 Jul 1969
TL;DR: In this paper, the authors measured ultrasonic absorption in aqueous solutions of sodium caprylate and sodium caprate at 30°C over the frequency range of 5 −95 mc.
Abstract: The ultrasonic absorption has been measured in aqueous solutions of sodium caprylate and sodium caprate at 30°C over the frequency range of 5–95 mc. As in the case of sodium dodecyl sulfate, the excess absorption was observed only in solutions in which the concentration was higher than the critical micellar concentration (CMC), both in the presence and absence of salt. The mechanism for these features was attributed to the reaction M ″→M′ + 3 N a + for sodium caprylate and M ″→M′ + 2.5 N a + for sodium caprate, where M′ and M″ are two types of micelle. The rate constants of the forward and backward reactions were 3.8 × 107 sec−1, 3.3 × 109 mole−3 sec−1 for sodium caprylate and 1.1 × 107 sec−1, 2.8 × 109 mole−2.5 sec−1 for sodium caprate, respectively. Some kinetic characteristics including the free energy, enthalpy, and entropy were calculated.
TL;DR: The heat and entropy change of micelle formation were constant and positive between 15 and 55°, which indicates that the latter is responsible for the formation of micelles and the corresponding increase in randomness was attributed mainly to water surrounding the hydrocarbon chains of single surfactant molecules and trapped in their coiled polyoxyethylene chains
TL;DR: In this paper, an NMR technique was used to determine CMC values at 35°C for octanoic, decanoie, laurie, and myristic acids in 95.5% sulfuric acid and the laurylammonium salts of butyric, caprylic, and Laurie acids in CC14.
TL;DR: In this article, oil-soluble surfactants were used as solubilizing agents for a water-solubilized food dye in perchlorethylene and showed that the critical micelle concentration decreases linearly with increasing water/surfactant ratio.
01 Feb 1969
TL;DR: In this article, surface tension, electrical conductivity, light scattering and nuclear magnetic resonance measurements were carried out in aqueous solutions of a series of ω-phenylalkyltrimethylammonium bromides.
Abstract: Surface tension, electrical conductivity, light scattering and nuclear magnetic resonance measurements were carried out in aqueous solutions of a series of ω-phenylalkyltrimethylammonium bromides. The conclusion is summarized as follows.
1)
The pentyl and higher homologs form micelles in aqueous solutions, provided the concentration is larger than a definite value (CMC). As expected, CMC decreases and association number of a micelle increases with an increase in the alkyl-chain length.
2)
The butyl derivative does not form large aggregates that are qualified to be called “micelles”. No distinct CMC is observed.
3)
In a micellar solution, surfactant molecules are rapidly exchanged between micelles and bulk water phase.
4)
Critical micelle concentration is affected by the introduction of a phenyl group at the end of an alkyl chain in such a manner as if 2.7 methylene groups were introduced.
TL;DR: The critical micelle concentration of barium caproate has been determined by studying the density and viscosity of soap solutions in water-propanol-1 mixtures of varying composition as discussed by the authors.
Abstract: The critical micelle concentration of barium caproate has been determined by studying the density and viscosity of the soap solutions in water-propanol-1 mixtures of varying composition. Studies on solubility, density, viscosity and molecular conductivity confirm that the change in the nature of the micelles occurs between 50% and 60% propanol-1 concentrations.
TL;DR: Results of the equilibrium sorption experiments revealed that maximum sorption occurred in the region of the critical micelle concentration of the surface-active agent.
TL;DR: In this article, the influence of critical micelle concentration of an anionic surfactant on the removal of different types of soils (soot, paraffin oil or mixture of olive oil and oleic acid) from wool was investigated in a model system.
Abstract: An Modellsystemen wurde der Einflus der kritischen Mizellbildungskonzentration eines anionischen Tensids auf die Entfernung verschiedener Schmutzarten (Rus, Paraffinol oder Olivenol-Olsauremischung) von Wolle untersucht. Fur die Rus-und Olentfernung sind die grenzflachenaktiven Einzelionen und nicht die Mizellen verantwortlich. Die Rusentfernung erreicht bei der kritischen Mizellbildungskonzentration Ck wegen des sich bei Ck einstellenden konstanten Zetapotentials der Rusteilchen einen oberen Grenzwert. Wahrend das unpolare Ol durch Umnetzung abgehoben wird, ist fur die starkere Auswaschung des polaren Ols im Vergleich zum unpolaren Ol eine der Umnetzung sich uberlagernde Mischphasenbildung anzunehmen.
Influence of Critical Micelle Concentration on the Washing Action of Sodium Dodecyl Sulfate
The influence of critical micelle concentration of an anionic surfactant on the removal of different types of soils (soot, paraffin oil or mixture of olive oil and oleic acid) from wool was investigated in a model system. The interfacially active single ions and not the micelles are responsible for the removal of soot and oil. At a critical micelle concentration Ck the extent of removal of soot reaches the uppermost limit due to the constant zeta potential of the soot particles attained at Ck. Whereas the non-polar oil is removed by wetting, it is assumed that the higher degree of elution of the polar oil compared to the non-polar one is due to the superimposition of the wetting effect along with the formation of a mixed phase.
TL;DR: In this paper, the polarographic micelle point (PMP) values of non-ionic surfactants, viz., Nonidet P40, NonIDet P42 and Nonex 501 have been determined by a polarographic maximum suppression method in the presence of electrolytes (used for polarographic reduction).
Abstract: The polarographic micelle point (PMP) values of non-ionic surfactants, viz., Nonidet P40, Nonidet P42 and Nonex 501 have been determined by a polarographic maximum suppression method in the presence of electrolytes (used for polarographic reduction) and compared with the critical micelle concentration (c.m.c.) values of nonionic surfactants obtained by other methods (spectrophotometric and electrocapillary curves methods). The PMP values are always lower than those obtained by other methods. The difference in c.m.c. values is due to the presence of ions of depolarizer and supporting electrolytes. The presence of electrolytes is likely to influence the water structure, thereby causing a lowering in c.m.c. values.
TL;DR: In this article, the pendant drop technique was used to determine the shape of the surface tension (γ)vs. composition curve in the neighbourhood of the pure solvent composition in hexadecylamine solutions.
Abstract: Measurements by the pendant drop technique confirm that the self-dissociation of sulphuric acid is relatively unimportant in determining the shape of the surface tension (γ)vs. composition curve in the neighbourhood of the pure solvent composition. The surface tension (γ for 100% sulphuric acid at 30°= 50·6 dyne. cm.–1) is hardly affected by sulphur trioxide, but water causes a marked increase. Micellization is indicated in hexadecylamine solutions (critical micelle concentration 0·017m at 30°), which thus confirms the cryoscopic observations of Leisten and Walton. Dodecylamine, on the other hand, forms no micelles up to 0·2m in the pure solvent, as shown by the drop-weight method and by cryoscopy; but micelles are probably formed with this solute in more aqueous (98%) acids.
TL;DR: In this paper, the authors determined the adsorption of tritiated sodium dodecyl sulfate (TNaDDS) from aqueous solutions at the poly(monochloro-p -xylylene) interface by dip counting.