Micelle Formation In Solutions Research Articles

Active Control of Interfacial Properties: A Comparison of Dimeric and Monomeric Ferrocenyl Surfactants at the Surface of Aqueous Solutions

The surface activity and micellization of the dimeric, ferrocenyl surfactant Fc(CH2)8N+(CH3)2(CH2)3(CH3)2N+(CH2)8Fc 2Br- (DI2+), where Fc = ferrocene = [η5-C5H5]Fe[η5-C5H5], are compared and contrasted to those of the monomeric, ferrocenyl surfactant Fc(CH2)8N+(CH3)3Br- (I+) in aqueous solution. Dimeric DI2+, when compared to I+, was measured to be surface active in aqueous solutions of 0.1 M Li2SO4 at lower concentrations (0.001 mM of DI2+ versus 0.03 mM of I+) and found to possess a lower critical micelle concentration (cmc) (0.02 mM for DI2+ as compared to 2.0 mM for I+). Linear sweep cyclic voltammograms show that the (two) ferrocenes of DI2+ oxidize independently to form ferrocenium cations. Light-scattering measurements confirm that DI2+ forms micelles in solution and that oxidation of DI2+ to DI4+ is accompanied by the disassembly of micelles. Reduction of DI4+ back to DI2+ reforms the micelles. Measurements of surface tension demonstrate that oxidation of DI2+ to DI4+ leads to desorption of surfactant from the surface of aqueous solutions. Because DI4+ was not measurably surface active at concentrations less than 0.4 mM, oxidation of DI2+ to DI4+ made possible changes in surface tension of 21 mN/m over a range of concentrations that exceeded an order of magnitude (0.02−0.4 mM). Control of the oxidation state of I+, in contrast, permits changes in surface tension of 20 mN/m at one concentration (2.0 mM) only. Dimeric redox-active surfactants in combination with electrochemical methods do, therefore, permit active control of interfacial properties of aqueous solutions over a wider range of surfactant concentrations than is possible with the corresponding monomeric redox-active surfactant. Simple models for the standard free energies of micellization and adsorption can describe the lower cmc of DI2+ as compared to I+ and the wider range of concentrations over which oxidation of DI2+ leads to changes in surface tension as compared to I+.

Dependence of the form factor of ganglioside micelles on a conformational change with temperature

The gangliosides GM2, GM1 and GD1b, biological amphiphiles with a double tail hydrophobic part and an oligosaccharide chain headgroup, form micelles in solution. Light scattering experiments have shown that ganglioside micelles which have gone through a temperature cycle have a smaller molecular mass and hydrodynamic radius than those which have been kept at room temperature. This fact has been interpreted with the hypothesis that, with temperature, the ganglioside molecules undergo a conformational change which affects their micellar properties appreciably. Careful small angle X-ray experiments, aimed to confirm the light scattering data and to evidence differences in the micellar internal structure are presented. Ganglioside micelles are quite inhomogeneous particles with respect to X-ray scattering, since there is a large contrast variation between the inner lipid part and the external hydrated sugar layer. Experimental form factors are fitted with a double-shell oblate-ellipsoid model.

Thermal Hysteresis Phenomena in Micellar Solutions of Gangliosides: Theory and Experiments

Light scattering experiments show that micellar solutions of various gangliosides have a thermotropic behaviour which is irreversible with respect to temperature. Gangliosides, amphiphilic molecules of biological origin, form micelles in solution which decrease their average aggregation number upon heating. When a critical temperature is reached, any further cooling and heating cycle does not alter the micellar size. This process, not determined by a denaturation of the ganglioside molecule, is explained by considering the temperature-dependent coupling between micellar aggregation number and molecular conformation of ganglioside polar head groups. A simple model is proposed which assumes that the polar heads may exist in two different stable conformations, each of them with an energy dependent on its own internal structure and on the interactions with the surrounding heads at the micelle surface. The interconversion between the conformational minima is then described as a cooperative event, with a naturally emerging barrier due to collective effects which accounts for the experimentally observed irreversibilities. The model has some resemblances with the solidification process from an undercooled fluid, with the main difference that it deals with a confined two-dimensional system at the micellar surface.

Phase behavior of random and ABC triblock methacrylic polyampholytes with poly(vinyl alcohol) in water: effect of pH and salt

ABC triblock and random methacrylic polyampholytes of molecular weight 4,000 g mol −1 with various base-neutral-acid compositions were examined for their phase separation behavior, each in an aqueous mixture with poly(vinyl alcohol) of molecular weight 10,000 g mol −1. Potassium chloride concentration and solution pH were varied and the phase behavior was mapped on the pH-(KCl) space. The block copolymers presented a much broader phase separation region than the random copolymers. This difference may reflect the effect of the structure of the block copolymers which leads to the formation of micelles in solution. The two-phase region of the block copolymers extended over the whole range of potassium chloride concentrations employed in this study, from 0.0 to 0.75 M, and covered the pH range from two pH units below the polyampholyte isoelectric point up to two units above, with the exception of the points at alkaline pH without added salt. The two-phase region of the random copolymers extended from 0.0 to 0.1 M KCl and covered at most one unit in pH, centered near the isoelectric point. The two-phase region of the block copolymers comprised two regimes: the low salt concentration regime characterized by a compact polyampholyte precipitate in equilibrium with a low-viscosity poly(vinyl alcohol) phase; the high salt concentration and alkaline pH regime characterized by two coexisting low-viscosity phases. The one-phase region of the block copolymers extended in the acidic pH range and covered the whole salt concentration range. The ion type effect on the phase behavior of block polyampholytes was related to the position of the ion in the Hofmeister series: high concentrations of salt of low salting out ability resulted in a transition from a two- to a one-phase system.

A Dynamic Light Scattering Study of Micelle Formation in Solutions of Poly(2-ethyl-2-oxazoline-dimethylsiloxane) in Water-2-Propanol Mixtures

Solutions of poly(2-ethyl-2-oxazoline-dimethylsiloxane), PEOX-PDMS, diblock copolymers in water-2-propanol mixtures were studied by dynamic light scattering. A diblock consisting of PDMS block with M n =4.8 kg mol -1 and a PEOX/PDMS degree of polymerization ratio=3 displayed three regimes in mixtures of water and 2-propanol. Compact micelles formed in pure water and at low mole fractions of 2-propanol where the hydrophobic PDMS blocks formed the core and hydrophilic PEOX blocks formed the corona. At a critical 2-propanol mole fraction and at C p ≥1 g L -1 , anomalously large micelles were observed

Controlled polymerisation of silicic acids derived from mineral silicates. Part 3.? formation and reactions of Q x M y (O1/2R) z

The preparation of reactive intermediates, of the type QxMy(O1/2R)z(where Q = SiO4/2; M = Me3SiO1/2; R = Et), has been studied. The intermediates (partially trimethylsilylated silicic acid esters) have been characterised and average structures have been determined. The formation and stability, and hence reactivity, of the intermediates, have been studied with respect to inter- or intra-molecular condensations under various reaction conditions: temperature, acidity and phase-transfer agent. The stability of the intermediates has been attributed to the formation of micelles in solution. The intermediates have been shown to undergo condensations with silicic acids from another source, e.g. a silicate mineral, yielding higher-molecular-weight polyorganosiloxanes. The intermediates have also been shown to react with various heteromolecules, yielding polymers which contain aluminium, phosphate, silicones, tetraethylsilicate, ethylenediaminetetraacetic acid and phenol groups.

Ultrasonic relaxation and micelle formation in solutions of cetylpyridinium chloride in formamide

Ultrasonic relaxation and micelle formation in solutions of cetylpyridinium chloride in formamide

Comparison of the structural and rheological consequences of micelle formation in solutions of a model di-block copolymer

In the selective solvent, dodecane, the di-block copolymer polystyrene- b-(ethylene- co-propylene), with a narrow molecular-weight distribution, forms micelles with polystyrene cores. Small-angle neutron scattering experiments were used to investigate both core shape and dimensions and the intercore structure factors as temperature or concentration were varied. Monodisperse spherical structures with radii around 120 Å were observed. Above a critical concentration these were arranged in relatively ordered structures in which preferred orientations could easily be induced. The core diameter and the intercore spacing were dependent on sample thermal history. During shear the intercore structure became less ordered. The structural results correlate well with measurements of the dynamic viscosity measured in oscillatory shear, which also show a sharp change from gel-like to liquid behaviour at this critical concentration. Data are compared to model calculations in the regions where the particle form factor or where the interparticle structure factor dominate. In the latter case a hard core potential with a soft tail is found to give reasonable agreement with the data, and to allow changes with shear rate, with concentration or with temperature to be interpreted.

Chemical relaxation and equilibrium studies of association in aqueous solutions of bolaform detergents. 2. Hexadecane-1,16-bis(trimethylammonium bromide) and dodecane-1,12-bis(tributylammonium bromide)

The self association of dodecane-1,12-bis(tributylammonium bromide) and of hexadecane-1,16-bis(trimethylammonium bromide) (C 12Bu 6 and C 16Me 6, respectively) has been investigated by means of density, conductivity, emf, T-jump, and ultrasonic absorption. The results of conductivity and emf indicate no micelle formation in solutions of C 12Bu 6 up to concentrations of 5 × 10 −2 M. On the contrary conductivity, emf, and ultrasonic absorption studies reveal that C 16Me 6 forms micelles with an ionization degree close to 0.5 and a CMC of about 4.5 × 10 −2 M. These results are the first ones which clearly show micelle formation by bolaform detergents of the C m H 2 m+1 N(R) 3Br − type. The density data indicate that the volume change upon micellization is smaller than 1.5 cm 3/mole, which suggests a deep penetration of water into C 16Me 6 micelles. Some results, most notably the ultrasonic absorption ones, suggest a folding of the bolaform alkyl chain in the micellized as well as in the molecularly dispersed state. Nevertheless, the study of an alkane-α,ω-bis(trimethylammonium bromide) with an alkyl chain containing more than 16 carbon atoms appears necessary before a definite conclusion can be reached about the bolaform alkyl chain conformation.

ChemInform Abstract: STUDY OF MICELLE FORMATION IN SOLUTIONS OF ALKYLAMMONIUM CARBOXYLATES IN APOLAR SOLVENTS BY POSITRON ANNIHILATION TECHNIQUES

Chemischer InformationsdienstVolume 10, Issue 36 Article ChemInform Abstract: STUDY OF MICELLE FORMATION IN SOLUTIONS OF ALKYLAMMONIUM CARBOXYLATES IN APOLAR SOLVENTS BY POSITRON ANNIHILATION TECHNIQUES L. A. FUCUGAUCHI, L. A. FUCUGAUCHISearch for more papers by this authorB. DJERMOUNI, B. DJERMOUNISearch for more papers by this authorE. D. HANDEL, E. D. HANDELSearch for more papers by this authorH. J. ACHE, H. J. ACHESearch for more papers by this author L. A. FUCUGAUCHI, L. A. FUCUGAUCHISearch for more papers by this authorB. DJERMOUNI, B. DJERMOUNISearch for more papers by this authorE. D. HANDEL, E. D. HANDELSearch for more papers by this authorH. J. ACHE, H. J. ACHESearch for more papers by this author First published: September 4, 1979 https://doi.org/10.1002/chin.197936108AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue36September 4, 1979 RelatedInformation

Study of micelle formation in solutions of alkylammonium carboxylates in apolar solvents by positron annihilation techniques

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudy of micelle formation in solutions of alkylammonium carboxylates in apolar solvents by positron annihilation techniquesLuz Alicia Fucugauchi, Belkacem Djermouni, Edward D. Handel, and Hans J. AcheCite this: J. Am. Chem. Soc. 1979, 101, 11, 2841–2844Publication Date (Print):May 1, 1979Publication History Published online1 May 2002Published inissue 1 May 1979https://doi.org/10.1021/ja00505a006RIGHTS & PERMISSIONSArticle Views82Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (508 KB) Get e-Alerts Get e-Alerts

Anion association and micelle formation in solutions of hydrotropic and short-chain carboxylates

Abstract A survey is given of studies on the association processes, the changes in structure and the formation of micelles in solutions of alkali metal salts of various carboxylic acids. The substances investigated are normal and branched alkanoates with 1–8 carbon atoms, and typical hydrotropes such as hydroxybenzoate. The experimental methods have been measurement of activities of carboxylate ions, counterions, and solvent by potentiometry, vapor pressure osmometry and gas chromatography; calorimetric determination of enthalpies of mixing; NMR studies of relaxation times for protons and line widths of signals from counterions; dilatometric measurements of changes in density on mixing and potentiometric investigations of hydrolytic equilibria. In order to simplify the evaluation of the results, the solutions were given a high content of electrolyte, mostly by adding sodium chloride to an ionic strength of 3 c. It has been established that association occurs in solutions of all alkanoates except acetate and propionate; the results are less conclusive for the benzoates. The initially formed aggregates contain from 2 to 4 anions. Larger aggregates (micelles) are formed by alkanoates with more than four carbon atoms. The results support the view that these association processes are mainly results of structural changes in the solvent, i.e., the aggregates are held together by hydrophobic bonding.

Nuclear magnetic resonance evidence for micelle formation in solutions of sodium 4,4-dimethyl-4-silapentane-1-sulphonate containing paramagnetic ions

Micelle formation in solutions of sodium 4,4-dimethyl-4-silapentane-1-sulphonate is indicated by studies of chemical shifts and line-widths in the presence of paramagnetic species, and also by the dye titration technique. The implications of this are discussed.

Aggregation of Certain Medicinal Amines in Aqueous Solutions of Their Salts

The osmotic coefficient and the equivalent conductance of aqueous solutions of certain medicinal amine salts were determined in order to examine their aggregating properties. Procaine HCl and tripelennamine HCl formed small ionic micelles. Partially ionized micelles of approximately constant size were the main constituent of solutions of dibucaine HCl and bromodiphenhydramine HCl. Tetracaine HCl and diphenhydramine HCl formed aggregates of different sizes in their solutions. No definite conclusion could be drawn about the types of aggregates that were present in solutions of pyrilamine maleate. An apparent critical micelle concentration (CMC) was obtained only for dibucaine HCl and bromodiphenhydramine HCl. From the CMC values at 0° and 25° it was concluded that the standard enthalpy change associated with formation of micelles in solutions of these two salts was practically zero. This finding together with a negative change in the standard free energy of micellization indicated that the process of micelle formation was mainly an entropy effect.

CONDUCTANCES OF AQUEOUS SOLUTIONS OF SODIUM OCTANOATE AT 25° AND 35° AND THE LIMITING CONDUCTANCE OF THE OCTANOATE ION

Equivalent conductances, densities, and viscosities of aqueous solutions of sodium octanoate have been determined at 25° and 35 °C, at concentrations ranging from 0.0002 M to 2.8 M. The limiting equivalent conductances of the octanoate ion have been determined as 23.08 mhos and 29.09 mhos, at 25° and 35 °C respectively.Comparison has been made of our experimental conductances with those calculated, using the equations of Robinson–Stokes, of Falkenhagen–Leist, and of Fuoss.No evidence has been found of micelle formation in solutions of sodium octanoate.

Micelle Formation in Solutions of Some Isomeric Detergents.

Micelle Formation in Solutions of Some Isomeric Detergents.

Physico‐chemical studies on the application of insecticides to sheep fleece. II—the action of dilute solutions of cationic wetting agents on fleece

AbstractThe reaction of natural fleece with wetting agents changes sharply at a critical concentration near that for micelle formation in solution. This paper describes the behaviour of cationic wetting agents at concentrations below this critical value. Measurements of the apparent removal from aqueous solution (termed the ‘inactivation’) of cetylpyridinium chloride by samples of Scotch Blackface fleece over periods of time show that such inactivation is considerable, even after one minute. The inactivation has been determined from decrease in the interfacial activity of the solution after contact with the fleece.The high inactivation observed is due to grease and suint on the wool; inactivation by the cleaned fibres is relatively slight. Suint influences the interfacial activity of the solution by co‐precipitation between the long‐chain suint anions and the cetyl cations, and also by the introduction of inorganic salts. High adsorption, with some absorption, occurs at the grease surface. Consideration is given to the mutual interference between these two effects.The inactivation is directly proportional to concentration up to 0.0025M. and the isotherm is almost independent of grease and suint content of the fleece; reasons for this, and possible implications, are discussed.

The effect of salts and chain length on the critical concentrations of colloidal electrolytes

It is shown that the effect of salts upon the critical concentration for the formation of micelles in solutions of long-chain electrolytes can be treated by considering the mass law as applied to the equilibrium between the unassociated long-chain ions, counter-ions and the aggregate. From the experimental observations, it is possible in this manner to calculate the ratio of long-chain ions and counter-ions which enter into the micelle. Similar considerations lead to the development of an equation which describes the variation in critical concentration with paraffin chain length for long-chain paraffin salts processing the same polar head-group.

Determination of the Critical Concentration for Micelle Formation in Solutions of Colloidal Electrolytes by the Spectral Change of a Dye1

Determination of the Critical Concentration for Micelle Formation in Solutions of Colloidal Electrolytes by the Spectral Change of a Dye¹

Determination of Critical Concentrations for Micelle Formation in Solutions of Cationic Soaps by Changes in the Color and Fluorescence of Dyes

Determination of Critical Concentrations for Micelle Formation in Solutions of Cationic Soaps by Changes in the Color and Fluorescence of Dyes