Showing papers on "Aggregation number published in 1982"
TL;DR: In this article, an analysis of the decay of the fluorescence of micelle-solubilized pyrene has been used to obtain for the first time the variation of the surfactant aggregation number n in micellar solutions of sodium dodecyl sulfate (SDS) upon addition of increasing amounts of 1-pentanol, and of oil (dodecane or toluene), thereby forming an oil-in-water microemulsion.
Abstract: The analysis of the decay of the fluorescence of micelle-solubilized pyrene has been used to obtain for the first time the variation of the surfactant aggregation number n in micellar solutions of sodium dodecyl sulfate (SDS) upon addition of increasing amounts of 1-pentanol, and of oil (dodecane or toluene), thereby forming an oil-in-water (o/w) microemulsion. The polarity of the microenvironment of the micelle-solubilized pyrene, the intramicellar rate constant k/sub E/ for pyrene excimer formation, and the microviscosity eta sensed by dipyrenylpropane (DPyP) upon intramolecular excimer formation have been also investigated. The results indicate that the addition of pentanol to concentrated (> 0.2 M) SDS solutions results in an increase of n and a decrease of k/sub E/, eta, and microenvironment polarity. These effects have been associated with the transformation of the initially spherical SDS micelles into anisotropic (disk-shaped) large micelles upon dissolution of pentanol in the micelles. Upon addition of dodecane, eta goes through a minimum in the case of concentrated SDS + pentanol systems, but only shows a monotonous increase for less concentrated SDS + pentanol systems. For the former the variation of n has been attributed to a change of micelle shape from nonspherical to spherical, whereas formore » the latter the initially spherical micelles remain spherical upon dodecane solubilization. Similar variations of n are observed when dodecane is replaced by toluene in the case of dilute SDS + pentanol systems, whereas large differences are noted for concentrated SDS + pentanol systems. In the case where the results suggest the formation of oil-in-water microemulsion droplets, the calculations indicate that the oil core permeates part of the surfactant alkyl chains.« less
164 citations
TL;DR: In this article, a theoretical treatment of the concentration-dependent changes in ultrasonic velocity is proposed from which information concerning the volume change on micellization may be obtained, which is related to the reversible thermal gelation of this block copolymer.
156 citations
TL;DR: In this paper, the effects of polydispersity on fluorescence quenching in micelle systems are discussed theoretically, and predictions are tested on computer generated fluorescence decay data.
Abstract: The effects of polydispersity on fluorescence quenching in micelle systems are discussed theoretically. Predictions are tested on computer generated fluorescence decay data for quenching in polydisperse micelle systems. It is shown that the estimated parameters, i.e, aggregation numbers and rate constants, are highly dependent on the micelle size distribution, and on the dynamic properties of the solubilizate–micelle system. Two extreme cases are considered: a static one, where no size changes of the micelles occur during the residence time, and a dynamic one where very large size variations take place. In the static case, the estimated aggregation number will decrease with quencher concentration from the weight average aggregation number in the limit of zero quencher concentration. In the dynamic case, the number average aggregation number is obtained, independent of quencher concentration. The initial decay constant contains information about the aggregation numbers, and in the generated data, this coul...
95 citations
01 Apr 1982
TL;DR: In this paper, critical micelle concentrations (CMC) were determined for tetradecyltrimethylammonium bromide in water from 25 to 166°C using a flow conductance cell.
Abstract: Critical micelle concentrations (CMC) were determined for tetradecyltrimethylammonium bromide in water from 25 to 166°C using a flow conductance cell. Over this temperature range the CMC increases by a factor of 10 and the degree of micelle dissociation increases from 0.25 to 0.65. The values of ΔH and ΔS for micellization are determined using the equilibrium model and are discussed in terms of the Benzinger compensation hypothesis for aqueous solutions.
89 citations
TL;DR: In this paper, the authors used a roughened two-shell model and found that the aggregation number increases from 15 ± 1 at 0.6 M to 23 ± 1 for octanoate micelles at 1.2 M.
85 citations
TL;DR: In this concentration range of overlapping rods, the data could be evaluated with a recently developed theory by Doi and Edwards for stiff rods.
Abstract: Conductivity, kinetic, static and dynamic light scattering, electric birefringence and rheological measurements were carried out on aqueous solutions of Tetradecylpyridinium-n-Heptanesulfonate (C14PyC7SO3) up to high concentrations. In dilute solutions between the critical micelle concentration (cmc) and another characteristic concentration (c
t) spherical micelles were detected whose radii were independent of detergent concentration and equal to the length of a detergent molecule; the aggregation numbern of these micelles of about 100 monomers per micelle was also in agreement with the existence of normal spherical micelles of aC
14-detergent. Above the concentrationc
t, the spherical micelles were found to grow to rodlike aggregates whose short axis was still independent of concentration and equal to the length of a monomer, while the lengthsL of the rods increased with increasing detergent concentration. When the lengthsL of the rods became comparable with the mean distancea between them, the starting interaction between the rods slowed down their growth. In this concentration range of overlapping rods, the data could be evaluated with a recently developed theory by Doi and Edwards for stiff rods. The rods reached finally a maximum length of about 500 a and decreased again in size upon further increase of concentration when the overlap ratioL/a reached a value of about 1,5.
68 citations
TL;DR: In this article, the size and shape of SDBS micelles were investigated using quasi-elastic light scattering data, and the results indicated that large, polydisperse micellar aggregates are present, and that the size of the aggregates depends on temperature, ionic strength, and in some cases the counterion.
63 citations
TL;DR: In this paper, the surface tension of dodecylammonium chloride solution has been measured as a function of temperature at concentrations around its critical micelle concentration (CMC), and the derivative of surface tension with respect to temperature has been observed to change abruptly at the CMC and then decrease very slowly with increasing concentration.
58 citations
TL;DR: In this article, the effect of 1-pentanol on the micellar properties of aqueous tetradecyltrimethylammonium bromide solutions (TTAB) was investigated when H2O is progressively substituted by D2O and when the hydrogenated alkyl chain of TTAB is replaced by a deuterated alyl chain.
54 citations
53 citations
TL;DR: In this article, the critical micelle concentration of mixtures of anionic and nonionic surfactants was measured and the physical basis of regular solution theory was shown to be consistent with the charge separation effect.
Abstract: The critical micelle concentration of mixtures of anionic and nonionic surfactants was measured. The anionic surfactants were alkylbenzene sulfonates and the nonionic surfactants were polyoxyethylene nonylphenols and a polyoxy-ethylene alcohol. The effect of added electrolyte, the number of ethylene oxide units in the polyethoxylate, and the anionic alkyl chain length were studied. All systems showed substantial negative deviations (lower CMC) from ideal solution theory. The results can be represented by regular solution theory. Charge separation appears to be the source of the nonideality. This considers the reduction of electrostatic repulsion between the ionic surfactant head groups in the mixed micelle, due to the insertion of nonionic hydrophilic groups between these charged groups, to be the cause of enhanced micelle formation. The physical basis of regular solution theory was shown to be consistent with the charge separation effect.
TL;DR: In this article, the interpretation of micelle diffusion coefficients, especially those obtained by means of quasi-elastic light-scattering spectroscopy (QELSS), is discussed in light of theoretical work on macro-particle diffusion.
01 Oct 1982
TL;DR: In this paper, the authors derived equilibrium constants to characterize interactions of hydrocarbons with solubilization sites assumed to consist of units of four deoxycholate anions.
Abstract: Vapor pressure—solubility data were obtained for the aqueous systems benzene—sodium deoxycholate and cyclohexane—sodium deoxycholate at 25°C. The results are consistent with a mass action model similar to the BET equation. Equilibrium constants are inferred to characterize interactions of hydrocarbons with solubilization sites assumed to consist of units of four deoxycholate anions. Although addition of sodium chloride increases the micelle aggregation number (Ref. (16)), solubilization results are affected very little by variation in salt concentration. When pure liquid hydrocarbon standard states are employed, solubilization results for benzene and cyclohexane (at varying salt concentrations) are quite similar.
01 Dec 1982
TL;DR: In this paper, the critical micelle concentration, aggregation number, and binding properties of decyltrimethylammonium ion micelles were determined as a function of counterion geometry using the dianions of phthalic, isophthalic and terephthalic acids.
Abstract: The critical micelle concentration, aggregation number, and binding properties of decyltrimethylammonium ion micelles are determined as a function of counterion geometry using the dianions of phthalic, isophthalic, and terephthalic acids. Light-scattering methods were used to secure the CMC and AN data whereas binding data were obtained with a specific ion electrode. It is shown that the differences among the micellar parameters are quite small relative to counterion effects induced by variations in polarizability and hydrophobicity. The data are used as evidence for a disorganized micelle surface containing water-filled grooves and fatty patches which do not discriminate among various geometric dispositions of the carboxylates about the aromatic ring.
TL;DR: In this paper, the authors investigated the properties of dialkylmethylammonium chloride (DMC) surfactants and found that the relaxation times and dissociation rate constants are close to those found for monoalkyl surfactant of about the same alkyl chain length.
Abstract: The kinetic results of the dialkylmethylammonium chloride surfactants of relatively short chain length investigated in this study do not show drastic changes compared to the result obtained for monoalkyl surfactants. Perhaps the most striking results is that the relaxation times and the dissociation rate constants are close to those found for monoalkyl surfactants of about the same alkyl chain length. The critical micelle concentrations are in agreement with previous studies on diaklyldimethylammonium chlorides. The aggregation number determined by /sup 13/C NMR for dihexylmethylammonium chloride is in agreement with results obtained for monoalkylammonium surfactants. The kinetic study of dialkylammonium surfactants of longer chain length would perhaps show larger differences but should be performed by other techniques. Shock-tube methods could be used to look for relaxation processes in aqueous solution of dialkylammonium surfactants of at least 9 carbon atoms per alkyl chain. 48 references.
01 Oct 1982
TL;DR: In this paper, the authors evaluated the dependence of m on the total detergent concentration from stopped-flow amplitudes (i.e. from concentration-jump experiments) and found that the mean aggregation number of these detergents appears to increase with increasing detergent concentrations, in accord with the results of other authors who have found an increase of m with increasing concentration of an added electrolyte.
Abstract: The analysis of the amplitudes in T-jump experiments on aqueous micellar solutions yields the dependence of the critical micelle concentration and the mean aggregation number m of the micelles on temperature, whereas p-jump experiments yield the corresponding dependence on pressure. In this paper we have, accordingly, evaluated the dependence of m on the total detergent concentration from stopped-flow amplitudes (i.e. from concentration-jump experiments). The experiments were performed on H2O-NaDS and H2O-NaDS. It turned out that the mean aggregation number of these detergents appears to increase with increasing detergent concentration, in accord with the results of other authors who have found an increase of m with increasing concentration of an added electrolyte.
01 Mar 1982
TL;DR: In this article, the aggregation of DBP − in aqueous solutions has been investigated by ESR of its vanadyl complex as well as by 31 P and 13 C NMR.
Abstract: The aggregation of DBP − in aqueous solutions has been investigated by ESR of its vanadyl complex as well as by 31 P and 13 C NMR. In a concentration range of 1 to 3 molar, the ESR measured reorientation correlation times and the 31 P relaxation indicate a mean aggregation number of 10, as confirmed by light scattering. A sharp transition is observed by 31 P relaxation at [DBP − ] = 3 M which corresponds to the formation of a liquid crystalline phase characterized by polarizing microscope observation.
TL;DR: In this article, the authors investigated the kinetics of triplet 1-bromonaphthalene and quencher pyrene in an aqueous micellar detergent solution.
TL;DR: This exceedingly slow equilibration of the liponucleotide 1-beta-D-arabinofuranosylcytosine 5'-diphosphate L-1,2-diacylglycerol (ara-CDPdiacyLglycersol) spontaneously forms vesicles which are several microns in diameter and probably unilamellar.
TL;DR: In this article, the size distribution of micelles, their surface tension, and the CMC of a single micelle are established. And the Gibbs-Curie generalized principle is used to analyze modifications for miceelles.
01 Jun 1982
TL;DR: A series of 4-alkylamido-2-hydroxybenzoic acids, containing 8−16 carbon atoms in the alkylamido group, has been synthetized and characterized as mentioned in this paper.
Abstract: A series of 4-alkylamido-2-hydroxybenzoic acids, containing 8–16 carbon atoms in the alkylamido group, has been synthetized and characterized. Surface tension measurements on aqueous solutions have been used to estimate the critical micellar concentrations and the area per molecule at the liquid-air interface. Light scattering measurements allowed to calculate the aggregation number and the hydrodynamic radius of the micelles.
01 Jan 1982
TL;DR: In this paper, the size of the aggregates is strongly dependent on the electrolyte concentration in the surfactant solution and it is suggested that the essential requirement for building up recovery activity is to make large aggregates with a certain size.
Abstract: Membrane osmometry and Coulter counter measurement have been used to study the size of the surfactant aggregates in solutions used in tertiary recovery. The size of the aggregates is strongly dependent on the electrolyte concentration in the surfactant solution. The aggregate size in the optimum recovery activity region (in terms of electrolyte concentration) is around 1 μ. The particles in the active solutions show a strong effect on polarized light. It is suggested that in aqueous surfactant systems, the essential requirement for building up recovery activity is to make large surfactant aggregates with a certain size. Mechanisms based on the size requirement of the surfactant aggregates have been used to describe the sodium and calcium requirements in optimum salinity regions of a chemical slug in the presence and absence of NE0D0L® 25-3S. The interaction between sodium and calcium ions with petroleum sulfonate and NE0D0L 25-3S was studied using specific ion electrodes.
TL;DR: In this paper, diffusion coefficients of tetradecyltrimethylammonium bromide in aqueous solutions have been determined at 25, 95 and 135 °C using the Taylor dispersion technique.
Abstract: Diffusion coefficients of tetradecyltrimethylammonium bromide in aqueous solutions have been determined at 25, 95 and 135 °C using the Taylor dispersion technique. The diffusion coefficient exhibits a minimum at a surfactant concentration above the critical micelle concentration (CMC). The results are interpreted in terms of electrostatic coupling and rapid exchange between micelle, surfactant monomer and counterions.
01 Jan 1982
TL;DR: In this review, the available experimental information about the micellar properties of gangliosides is collected and critically compared and the properties of mixed micelles with a non-ionic commercial amphiphile, Triton X-100, are discussed.
Abstract: Gangliosides are amphiphilic biological lipids, having a hydrophilic part made of an oligosaccharide chain containing one or more molecules of sialic acid, and a hydrophobic part made of two long aliphatic chains belonging to a sphingosine and a fatty acid residue. The interactions of gangliosides with biological molecules and membranes may be considerably influenced by the state of aggregation of ganglioside molecules. In this review, the available experimental information about the micellar properties of gangliosides is collected and critically compared. The most significant data are the following: the probable value of the critical micelle concentration is in the range 10-10 − 10-8 M, the aggregation number is between 200 and 350, the hydrodynamic radius is about 60 A, and the micellar shape is probably an oblate ellipsoid (disklike micelle) with an axial ratio about 2. The properties of mixed micelles with a non-ionic commercial amphiphile, Triton X-100, are also discussed.
TL;DR: In this article, the authors measured ultrasonic absorption in hexane solutions of octylammonium alkanoates (nonanoate, decanoate and dodecanoate) and determined the value of critical micelle concentration (CMC) was determined to be 0.02 M (1 M = 1 mol dm−3) for all the surfactants.
Abstract: Ultrasonic absorption was measured in hexane solutions of octylammonium alkanoates (nonanoate, decanoate, dodecanoate, and tetradecanoate). The value of critical micelle concentration (CMC) was determined to be 0.02 M (1 M=1 mol dm−3) for all the surfactants. The excess ultrasonic absorption, observed in the solutions above the CMC, was ascribed to the association-dissociation of the monomer to and from the micelle. From the concentration dependences of the ultrasonic parameters, the mean aggregation number of the micelle, the rate constants, and the enthalpy change of the above reaction were obtained. These results were discussed in relation to the shape of the reversed micelle and the solute-solvent interactions.
DOI•
01 Feb 1982TL;DR: In this paper, the effect of surfactants on the absorption and emission properties of thionine (TH+) have been studied in detail, and the association constant for the formation of the TH+-SLS complex in the premicellar region and the binding constant for incorporation of the dye into the micelle in the micellar regions have been computed.
Abstract: The effect of surfactants on the absorption and emission properties of thionine (TH+) have been studied in detail. Among the various surfactants investigated sodium lauryl sulphate (SLS) has marked effect on these properties. Changes in the absorption spectrum and the decrease in fluorescence intensity at [SLS] below the critical micelle concentration (CMC) are attributed to the formation of a dye-surfactant complex. At [SLS] above CMC, the restoration of dye spectrum with increased extinction coefficient at the λmax and a small but definite red shift of the λmax are interpreted as due to the incorporation of the dye into the SLS micelle. The absorbance and spectral shift data suggest the thionine cation to be localized near the micelle Stern layer in the case of SLS micelles but completely outside the micelle in the aqueous environment in the case of CTABr. From the absorbance and fluorescence data, the association constant for the formation of the TH+-SLS complex in the premicellar region, and the binding constant for the incorporation of the dye into the micelle in the micellar region have been computed. The values of both these constants were found to increase markedly in the presence of electrolytes.
01 Jan 1982
TL;DR: In this paper, the critical micelle concentration (CMC) in aqueous solution, effective chain length (neff), and hydrophobicity of various straight chain ionic surfactants containing two or more polar functional groups at one end or at opposite ends of an amphiphile molecule were considered.
Abstract: The critical micelle concentration (CMC) in aqueous solution, effective chain length (neff, and hydrophobicity of various straight chain ionic surfactants containing two or more polar functional groups at one end or at opposite ends of an amphiphile molecule — are considered.
TL;DR: In this paper, the electronic absorption spectra of different acid dyes, mainly C. I. Acid Red 13, 18, 27, 88 and 141, have been investigated in aqueous and non-aqueous solutions.
Abstract: The electronic absorption spectra of different acid dyes, mainly C. I. Acid Red 13, 18, 27, 88 and 141, have been investigated in aqueous and non-aqueous solutions. As the concentration of the dye increases the absorption spectrum shifts to shorter wavelengths; this behaviour has been attributed to the formation of higher aggregates. The longer wavelength band, most marked in dilute solutions, is typical of the monomeric dye. The aggregation of these dyes were studied quantitatively using the Maximum Slope Method. The monosulfonic acid dyes Red 141 and 88 and the disulfonic acid dye 13 are aggregated at room temperature with an average aggregation number of 2.0, 2.2 and 1.5, respectively. The trisulfonic acid dyes Red 18 and 27 show very little aggregation at this temperature.
TL;DR: Pancreatic lipase activity toward vinyl laurate (VL) solubilized in sodium deoxycholate (NaDC) micelles was investigated kinetically and it was shown that Km indicates the lower limit of the dissociation constant of lipase-NaDC micellesolubilizing VL, K1.
Abstract: Pancreatic lipase activity toward vinyl laurate (VL) solubilized in sodium deoxycholate (NaDC) micelles was investigated kinetically. The inhibition by substrate-free NaDC micelles, M, was observed, and a Lineweaver-Burk plot and a plot of the reciprocal of initial rate vs. [M] indicated that the inhibition may be fully competitive or fully mixed inhibition, depending on the value adopted for the aggregation number of NaDC micelles. However, further consideration of the interaction of various species in the system led us to favor a fully competitive inhibition mechanism. The Michaelis constant, Km, and the inhibition constant, K4, which is the dissociation constant of lipase-NaDC micelle complex, were estimated. It was shown that Km indicates the lower limit of the dissociation constant of lipase-NaDC micelle solubilizing VL, K1. The results are discussed in relation to the results of other studies on the inhibition of the enzyme by bile salts in emulsion systems.
Journal Article•
TL;DR: The kinetics of quenching of luminescent probes in micellar systems are treated, the dependence of the total luminescence intensity on quencher concentration, and mechanisms for migration of solubilized molecules between micelles are discussed.
Abstract: A previous study treated the kinetics of quenching of luminescent probes in micellar systems, assuming that the distribution of solubilized molecules among the micelles obeys Poisson statistics. This work extends the treatment to a more general case where there is a limit to the number of solubilized molecules in any one micelle. The rate constant for exit of a quencher molecule from a micelle containing n quencher molecules is still assumed to be given by nk-. It is assumed that the luminscent probe is dissolved exclusively in the micellar phase. Sections of this work treat the decay kinetics of excited probes in the presence of a quencher, investigate the dependence of the total luminescence intensity on quencher concentration, and discuss mechanisms for migration of solubilized molecules between micelles. 20 references.