Showing papers on "Critical micelle concentration published in 1993"
TL;DR: The phase behavior of the triblock copolymers dissolved in water has been studied using SANS as discussed by the authors, and the structural properties have been studied as a function of polymer concentration and temperature.
Abstract: The phase behavior of the triblock copolymers dissolved in water has been studied using SANS. The structural properties have been studied as a function of polymer concentration and temperature. At low temperature (T ≤ 15°C) and low polymer concentrations the unimers are fully dissolved Gaussian chains with radius R g =17 A. Close to ambient temperature, the hydrophobic nature of PPO causes aggregation of the polymers into spherical micelles with core sizes of the order of 40-50 A, somewhat temperature dependent. The concentration of micelles increased roughly linearly with temperature, until either a saturation is reached,where all the polymers are part of a micelle, or the volume density of micelles is so high that they lock into a crystalline structure of hard spheres
669 citations
TL;DR: In this article, the synthesis of dendritic polyether macromolecules based on a 3, 5-dihydroxybenzyl alcohol building block and having carboxylate groups as chain-ends is described.
Abstract: The synthesis of dendritic polyether macromolecules based on a 3, 5-dihydroxybenzyl alcohol building block and having carboxylate groups as chain-ends is described. These novel macromolecules behave as unimolecular micelles and their ability to solvate hydrophobic molecules has been investigated by UV–VIS spectroscopy. A dramatic increase in the saturation concentration of various polycyclic aromatic compounds in water was observed which was of a magnitude similar to that observed for micelles derived from sodium dodecyl sulfate. A relationship between the solubilizing power of the dendrimer and the electron density of the polycyclic aromatic was found. A linear relationship between the solubilizing ability and the concentration of the dendrimer, even at concentrations as low as 5 × 10–7 mol dm–3, indicates that these materials do not have a critical micelle concentration. Increases in the ionic strength of an aqueous solution of the dendrimer caused an increase in the saturation concentration of the hydrophobic molecules. A recyclable solubilization and extraction system is discussed. The synthesis of a globular dendritic macromolecular amphiphile designed to reside at the interface of an organic solvent and water is also described. This ‘hybrid’ dendritic amphiphile consisting of two distinct sectors, one hydrophilic and the other hydrophobic is prepared by stepwise alkylation of a core molecule, 4,4′-dihydroxybiphenyl with the two dissimilar dendritic fragments.
467 citations
TL;DR: Arthrofactin is one of the most effective lipopeptide biosurfactants and was a better oil remover than synthetic surfactants, such as Triton X-100 and sodium dodecyl sulfate.
Abstract: A biosurfactant termed arthrofactin produced by Arthrobacter species strain MIS38 was purified and chemically characterized as 3-hydroxydecanoyl-D-leucyl-D-asparagyl-D-threonyl-D- leucyl-D-leucyl-D-seryl-L-leucyl-D-seryl-L-isoleucyl-L-isoleucyl-L-as paragyl lactone. Surface activity of arthrofactin was examined, with surfactin as a control. Critical micelle concentration values of arthrofactin and surfactin were around 1.0 x 10(-5) M and 7.0 x 10(-5) M at 25 degrees C, respectively. Arthrofactin was found to be five to seven times more effective than surfactin. The minimum surface tension value of arthrofactin was 24 mN/m at a concentration higher than the critical micelle concentration. According to the oil displacement assay, arthrofactin was a better oil remover than synthetic surfactants, such as Triton X-100 and sodium dodecyl sulfate. Arthrofactin is one of the most effective lipopeptide biosurfactants. Images
348 citations
TL;DR: In this article, the micellization in an aqueous solution of polymers containing ethylene oxide and propylene oxide was modeled on the basis of a mean-field lattice theory for multicomponent mixtures of copolymers with internal states occurring in heterogeneous systems.
Abstract: The micellization in an aqueous solution of polymers containing ethylene oxide (EO) and propylene oxide (PO) was modeled on the basis of a mean-field lattice theory for multicomponent mixturesof copolymers with internal states occurring in heterogeneous systems. The critical micelle concentration, the aggregation number, and the hydrodynamic radius, as well as their temperature dependence of these, were examined for a number of Pluronic triblock copolymers and for two related block copolymers. A semiquantitative description of the strong temperature dependence of these quantities is observed experimentally for Pluronic F127 [(EO) 99 (PO) 68 (EO) 99 ] was obtained
241 citations
TL;DR: In this paper, the authors proposed that the association energy of collapsed spheres can be described by the Hamaker equation, i.e., that the interaction energy is proportional to the radius of the spheres.
Abstract: Block copolymers are generally polydisperse, and the molecular weight distribution of a block copolymer has a profound effect on its micellization behavior in solution. When the block copolymer concentration is lower than the mixed critical micelle concentration [cmc(mix)], the insoluble block is assumed to adopt a spherical collapsed conformation. This leads to the proposal that the association energy of the collapsed spheres can be described by the Hamaker equation, i.e., that the interaction energy is proportional to the radius of the spheres. From this model, a relationsbip between the cmc of each component and the length of the insoluble block can be obtained
233 citations
TL;DR: In this paper, a microbially produced compound, hydroxypropyl-β-cyclodextrin (HPCD), was investigated for its potential to increase the apparent aqueous solubilities of lowpolarity organic compounds.
Abstract: Hydroxypropyl-β-cyclodextrin (HPCD), a microbially produced compound, was investigated for its potential to increase the apparent aqueous solubilities of low-polarity organic compounds. The results show that the apparent solubilities of trichloroethene, chlorobenzene, naphthalene, anthracene, and p,p'-DDT were significantly increased in HPCD solutions. The relative aqueous-phase concentrations (S t /S o ) of the compounds increased linearly with increasing HPCD concentration. The solubilization power of HPCD is dependent on the size and relative polarity of its cavity, and, unlike micelle-forming surfactants, HPCD has no critical micelle concentration. The partition mechanism was shown to be a valid approach for interpreting the solubilization activity of HPCD
189 citations
TL;DR: In this paper, the authors measured the speed of sound at 298.15 K as a function of [surfactant] in the presence of various constant concentrations of β-Cyclodextrin and [β-CD] at different surfactant constant concentrations both in the premicellar and micellar regions.
Abstract: The encapsulation processes of sodium dodecyl sulfate (SDS) or sodium perfluorooctanoate (SPFO) monomers into the cavity of β-Cyclodextrin (β-CD) and its effect in the micellization process of the surfactant itself have been analyzed by measuring the speed of sound, u, at 298.15 K (a) as a function of [surfactant] in the presence of various constant concentrations of β-CD and (b) as a function of [β-CD] at different surfactant constant concentrations both in the premicellar and micellar regions. The predominant complex formed (β-CD:surfactant) in both cases has a stoichiometry of 1:1 and the association constants K have been determined from speed of sound measurements by using a semiempirical model proposed by us previously. The apparent critical micellar concentration, cmc*, is found to increase upon the addition of cyclodextrin, for both systems. However, the concentration of free surfactant available for the micellization process in the postmicellar region when the cyclodextrin is present, [surf]f, remains constant in the case of SDS + β-CD and presents an overall increase in the case of SPFO + β-CD. © 1993, American Chemical Society. All rights reserved.
137 citations
TL;DR: The water-soluble monomer dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (DAMAB) was synthesized as mentioned in this paper.
Abstract: The water-soluble monomer dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (DAMAB) was synthesized. This monomer possesses a critical micelle concentration of 4.9×10 -3 M. A series of copolymers of DAMAB with acrylamide (AM) have been prepared by radical copolymerization by micellar and solution techniques. The rheological properties of the copolymers were strongly affected by their microstructures. A random copolymer with 5 mol% of DAMAB obtained by solution polymerization in tert-butyl alcohol showed a tendency for intramolecular hydrophobic association, while microheterogeneous copolymerization of AM with 5 and 10 mol% of DAMAB in water yielded microblocky structures which promoted intermolecular association of hydrophobes
131 citations
TL;DR: In this article, the thermodynamics of micellisation for SDS and CTAB in the presence of various non-aqueous co-solvents were compared and it was shown that tetrahydrofuran (THF) has the highest ability to break the micelles.
Abstract: Conductances of sodium dodecylsulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) have been determined in the binary mixtures of ethylene glycol (EG)–H2O, glycerol (Gly)–H2O, N,N-dimethylformamide (DMF)–H2O and dimethyl sulfoxide (DMSO)–H2O. The measurements were made at 25 °C with EG concentrations up to 75 vol.% and other co-solvent concentrations up to 50 vol.%. Conductances of SDS have also been performed in the presence of L-glutamic acid, 18-crown-6 ether (CR) and sucrose in H2O. From the conductivity data, the critical micellar concentration, c.m.c., the counter ion dissociation constant, β, the standard Gibbs' free energy change of the micellisation, ΔG⊖m, and in some cases the molar equivalent conductance at infinite dilution, Λ0, of these surfactants have been determined.A comparative study of the thermodynamics of micellisation for SDS and CTAB in the presence of various non-aqueous co-solvents reported here and earlier, reveals that tetrahydrofuran (THF) has the highest ability to break the micelles. On the other hand, the presence of additives like glutamic acid, CR and sucrose lead to micelle stabilisation.
130 citations
TL;DR: In this paper, a new method was developed for determining binding constants of cyclodextrins with surface-active compounds, including water-soluble ionic surfactants.
Abstract: A new method has been developed for determining binding constants of complexes of cyclodextrins with surface-active compounds, including water-soluble ionic surfactants. The technique requires measuring the change in surface tension caused by addition of a cyclodextrin (CD) to aqueous solutions of the surfactant; the experimental results lead directly to inferred values of the thermodynamic activity of the surfactant. Surface tension results are reported for three different surfactants sodium dodecyl sulfate (SDS), cetylpyridinium chloride (CPC), and cetyltrimethylammonium bromide (CTAB) in the presence and in the absence of added [beta]-CD. Data for CPC have been obtained at surfactant concentrations below and above the critical micelle concentration. Correlations between surface tension and surfactant activity are expressed by the Szyszkowski equation, which subsumes the Langmuir adsorption model and the Gibbs equation. It is observed that the surface tension increases monotonically as [beta]-cyclodextrin is added to ionic surfactant solutions. At concentrations of CD well in excess of the surfactant concentration, the surface tension approaches that of pure water, indicating that neither the surfactant-CD complexes nor CD itself are surface active. Binding constants are inferred from a model that incorporates the parameters of the Szyszkowski equation and mass action constants relating to the formation of micellesmore » from monomers of the surfactant and the counterion. Evidence is given that two molecules of CD can complex the C-16 hydrocarbon chain of the cetyl surfactants. 30 refs., 5 figs., 1 tab.« less
121 citations
TL;DR: In this article, the interfacial behavior of diblock copolymers where one of the blocks is a weakly charged polyelectrolyte and the other block is an organic polymer insoluble in water is discussed.
Abstract: The interfacial behavior of diblock copolymers where one of the blocks is a weakly charged polyelectrolyte and the other block is an organic polymer insoluble in water is discussed. In solution in water, for a fixed composition, the copolymer forms spherical micelles if the fraction of charged monomers is smaller than a critical value. From a micellar solution, charged copolymers can adsorb at both an airwater and a solid-water interface. However in both cases, strong adsorption and the formation of a dense polyelectrolyte grafted layer (brush) is possible only if the electrical charge is small enough. The adsorption isotherm reaches a plateau when the concentration is raised above the critical micellar concentration where the energetic properties of the layer are dominated by the neutral sequence
TL;DR: The development of a simple, reliable method for determination of detergent micelle aggregation number that relies solely on measurement of steady-state fluorescence quenching is presented.
TL;DR: In this article, the Gibbs excess adsorption equation was used to reinterpret the surface tension data in terms of the Gibbs equilibrium for the formation of micelle formation in petroleum fractions.
TL;DR: In this paper, the adsorption of SDS to polystyrene latex particles of low negative charge was examined as a function of surfactant concentration by estimation of the hydrodynamic radius and also the zeta potential (ζ) by electrophoretic measurements.
Abstract: The adsorption of sodium dodecyl sulfate (SDS) to polystyrene latex particles of low negative charge has been examined as a function of surfactant concentration by estimation of the hydrodynamic radius and also the zeta potential (ζ) by electrophoretic measurements. Adsorption isotherms were also determined by a surface tension method. Adsorption at zero and low ionic strength (10 -3 M) is two-stepped: an initial hydrophobically-driven adsorption of single surfactant molecules followed at increased SDS concentrations by a cooperative adsorption at SDS concentration close to the critical micelle concentration (cmc)
TL;DR: In this paper, a new surface apparatus was used to study the interactions between glass surfaces immersed in CTAB (cetyltrimethylammonium bromide) solutions.
Abstract: A new surface apparatus has been used to study the interactions between glass surfaces immersed in CTAB (cetyltrimethylammonium bromide) solutions. At low surfactant concentrations CTAB adsorbs to form a monolayer, and the surfaces become adhesive in contact. At a concentration of 5×10 -5 M the charge on glass is neutralized, and the surfaces experience an attractive force in excess of that expected from van der Waals interactions. At concentrations just below the critical micelle concentration, CTAB adsorbs to the hydrophobic interface to form loosely packed bilayers, but the surfaces always come to an adhesive minimum
TL;DR: In this article, a micellar solution and its CMCs and partial specific volumes at different temperatures were measured and the relationship between the molecular structures of solutaes and the resulting thermodynamic quantities was investigated.
Abstract: Micellar electrokinetic chromatography (MEKC) allows the calculation of distribution coefficients between a micelle and the surrounding aqueous phase from the measurement of the migration time, provided the critical micelle concentration (CMC) and the phase ratio are known. Thermodynamic quantities such as enthalpy and entropy changes of micellar solubilization were calculated from the temperature dependence of the distribution coefficients. Sodium dodecyl sulfate (SDS) was employed to prepare a micellar solution and its CMCs and partial specific volumes at different temperatures were measured. The relationship between the molecular structures of solutaes and the resulting thermodynamic quantities was investigated. The temperature inside the capillary was calculated from the temperature dependence of the distribution coefficient.
TL;DR: In this article, a method for determining the concentration of micelles is proposed, which is based on the concept of a mouselles being versatile chemicals which, at a sufficiently high concentration, will arrange themselves into organized molecular assemblies known as micells.
Abstract: Surfactants are versatile chemicals which, at a sufficiently high concentration, will arrange themselves into organized molecular assemblies known as micelles. This paper examines a method for determining this concentration.
TL;DR: In this paper, photo-initiated polymerization of these surfactants in the micellar state led to stable and transparent or slightly bluish systems with high molecular weights.
Abstract: Cationic surfactants bearing a polymerizable styryl headgroup and a variable alkyl chain (Cn-STY with n=8, 12, and 16) have been synthesized. Their aqueous solutions have been characterized by the surfactant critical micellar concentration (cmc) and aggregation number. The photoinitiated polymerization of these surfactants in the micellar state led to stable and transparent or slightly bluish systems. The polymers have high molecular weights (3x10 5 -3x10 6 ) which indicate that the initial micellar structure is not preserved upon polymerization
TL;DR: In this paper, the homogeneous asymmetric hydrogenation of (Z)-methyl-α-acetamidocinnamate catalyzed by the system [Rh(COD)2]BF4 + 1.1 BPPM could be effected in water as medium in the presence of micelle-forming amphiphiles.
TL;DR: In this paper, an argon plasma treatment was used to immobilize a reversibly adsorbed surface active compound (sodium dodecyl sulfate, SDS) onto a hydrophobic substrate (poly(propylene), PP).
TL;DR: Added selectivity, provided by the surfactant properties of CTAC, played a critical role in resolving closely related tripeptides as well as larger bioactive peptides.
TL;DR: The slow relaxation time (τ2) of micelles, measured by the pressure-jump technique, was maximum at 200 mM concentration at 25°C, indicating that the most stable mouselles are formed at this concentration as discussed by the authors.
Abstract: The slow relaxation time (τ2) of sodium dodecyl sulfate (SDS) micelles, measured by the pressure-jump technique, was maximum at 200 mM concentration at 25°C, indicating that the most stable micelles are formed at this concentration. This is presumably related to the optimum molecular packing in the micelle. The rate of solubilization of benzene and Orange OT dye into SDS solutions was also maximum at 200 mM concentration. The results are explained as follows: The distance between micelles (i.e., intermicellar distance) decreases as the surfactant concentration (or the number of micelles) increases, resulting in a stronger electric repulsion between micelles. Therefore, the micelles become more rigid, due to the compressive force of intermicellar repulsion, as the concentration increases up to 200 mM SDS. With further increase in the SDS concentration, the micellar shape changes from spherical to cylindrical to accommodate more surfactant molecules in the solution and to minimize the free energy of the system. The interior of the tightly packed micelles is more hydrophobic than that of loosely packed micelles and, therefore, the tightly packed micelles induce rapid solubilization of nonpolar molecules (e.g., benzene, Orange OT) into these micelles.
TL;DR: In this article, soap-type surfactants bearing a 1,3-dioxolane ring were prepared in good yields by acid-catalyzed condensation of 1-O-alkyl glycerols with oxocarboxylic acid esters, followed by alkaline hydrolysis without any expensive reagent and special equipment.
Abstract: New soap-type surfactants bearing a 1,3-dioxolane ring were prepared in good yields by the acid-catalyzed condensation of 1-O-alkylglycerols (alkyl: decyl, dodecyl, tetradecyl, heptadecyl, octadecyl, orcis-9-octadecenyl) with oxocarboxylic acid esters, followed by alkaline hydrolysis without any expensive reagent and special equipment. These surfactants were soluble in alkaline water at room temperature. Their critical micelle concentrations were much smaller than that of sodium dodecanoate. An alkaline solution of the octadecyl homologue was nonfoaming, but the other homologues, including thecis-9-octadecenyl derivative, showed high foaming ability in alkaline solutions. The structural effect of these compounds on the area per molecule at the surface is also discussed. Because these surfactants contain a 1,3-dioxolane ring, they can be utilized as a new acid-decomposable type of cleavable surfactant. At pH 1, they decompose almost completely into nonsurface-active species after 80 min.
TL;DR: In this paper, surface tension, heat capacity, and density of DDAO mixtures were measured at 25 o C as functions of the total molality, and the critical micelle concentration (cmc) as a function of the mixture composition deviated negatively from the ideal behavior.
Abstract: Surface tension, heat capacity, and density of the sodium dodecyl sulfate (NaDS)-dodecyldimethylamine oxide (DDAO) mixtures have been measured at 25 o C as functions of the total molality. The critical micelle concentration (cmc), derived from surface tension data, as a function of the mixture composition (X NaDS ) deviates negatively from the ideal behavior. The apparent molar volumes (V Φ,2 )and heat capacities (C Φ,2 ) of the mixture were calculated from density and heat capacity data. At a given X NaDS , V Φ,2 increases with the total molality tending to a constant value
TL;DR: In this paper, the enthalpies of solution (textdecoration:overlineH2-H02) of some homogeneous decyl poly(oxyethylene glycol) ether (C10En) surfactants in monomeric and micellar states in 3 and 6 mol dm-3 aqueous urea solutions have been determined calorimetrically in the temperature range 288.15-318.15 K.
Abstract: The enthalpies of solution (text-decoration:overlineH2–H02) of some homogeneous decyl poly(oxyethylene glycol) ether (C10En) surfactants in monomeric and micellar states in 3 and 6 mol dm–3 aqueous urea solutions have been determined calorimetrically in the temperature range 288.15–318.15 K. The enthalpies of micellization (ΔmicH) and the heat capacities of monomeric (ΔCp, mono) and micellar (ΔCp, mic) forms as well as the heat capacities of micellization (ΔCp, m) have been evaluated from the enthalpy data. ΔmicH is less positive in aqueous urea solutions than in water and decreases with increasing urea concentration and temperature. ΔCp, m is relatively higher in aqueous urea solutions. The results indicate a decrease in hydration or structure around monomers in the pre-c.m.c. (critical micelle concentration) region and a relative increase in hydration of micelles due to enhanced hydrogen bonding between ethylene oxide groups and urea molecules in the post-c.m.c. region. Interactions between polyoxyethylene (hydrophilic) groups and urea seem to dominate over decyl (hydrophobic) group–urea interactions.
TL;DR: An analysis of the fluorescence self-quenching efficiency of recovered vesicular CF after incubation with T, below an its critical micelle concentration suggests that micellar solutions of T were found to promote the catastrophic rupture ofr the membrane.
Abstract: Triton X-100 (T) in its monomeric form has been found to induce the leakage of 5(6)-carboxyfluorescein (CF) from tightly packed gel-phase vesicles derived from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC, 25 o C). In contrast, micellar solutions of T were found to promote the catastrophic rupture ofr the membrane. These conclusions are based on an analysis of the fluorescence self-quenching efficiency of recovered vesicular CF after incubation with T, below an its critical micelle concentration
TL;DR: In this paper, the visible spectra of safranine T in micellar solutions indicate 1:1 (dye to micelle) charge transfer complex formation with the non-ionic surfactants Triton X 100 (TX 100), Tween 20, Tween 40 and Tween 60.
Abstract: The visible spectra of safranine T in micellar solutions indicate 1:1 (dye to micelle) charge transfer complex formation with the non-ionic surfactants Triton X 100 (TX 100), Tween 20, Tween 40, Tween 60 and Tween 80 as well as with the anionic surfactant sodium dodecyl sulphate (SDS). The non-ionic surfactant micelles show stronger interaction than the ionic micelle SDS, the complexing strengths of the non-ionic micelles following the order Tween 80>Tween 60>TX 100>Tween 40>Tween 20. The fluorescence spectrum of the dye is also affected (intensified) by the surfactant micelles. The results confirm a 1:1 complex and comparable complexing strengths (except the position of TX 100) as revealed by the ground state spectra. Thermodynamic analysis shows that the increased stability of the dye—micelle complex is associated with a systematic increase in exothermic enthalpy and decrease in entropy which compensate each other. The equilibrium constants of the dye—micelle complex are directly proportional to the carbon numbers of the Tweens and inversely proportional to the critical micelle concentration (CMC) of the surfactants.
TL;DR: In this paper, the adsorption at the air/solution interface of the surfactant tetradecyltrimethylammonium bromide (C 14 -TAB) above its critical micelle concentration (cmc=3.7 mM) has been studied by neutron specular reflection.
Abstract: The adsorption at the air/solution interface of the surfactant tetradecyltrimethylammonium bromide (C 14 -TAB) above its critical micelle concentration (cmc=3.7 mM) has been studied by neutron specular reflection. The amount adsorbed increases with concentration steadily through and above the cmc. Combination of the surface tension and the surface excess, as determined by neutron reflection, has been used to determine the variation of the activity of the surfactant from the cmc up to 0.16 M. The structure of the adsorbed layer at a concentration 50 times the cmc is shown to consist of the usual monolayer of surfactant, an aqueous layer from which surfactant is absent, and a further layer of surfactant with about a 5% excess over the bulk solution
TL;DR: In this article, two new cationic surfactants containing a disulfide bond were synthesized, and the physical chemical characteristics and the fundamental surface-active properties were determined.
Abstract: Two new cationic surfactants containing a disulfide bond were synthesized, and the physical chemical characteristics and the fundamental surface-active properties were determined. These new surfactants have potential applications in the textile and cosmetic field. These compounds have been prepared by condensation of a commercial Nα,Nα-dimethyl amino betaine with cystine dimethyl ester or cystamine by means of the mixed anhydride method. The study of their properties revealed that these molecules are soluble in water (stable at pH⩽8) and show surface activity with similar low critical micelle concentration values. Microscopic examination of water/surfactant systems containing these compounds shows that they form liquid crystals with patterns corresponding to typical hexagonal and lamellar structures.