Showing papers on "Critical micelle concentration published in 2005"
TL;DR: The data suggests that the micelles of thioflavin T bind amyloid fibrils leading to enhancement of fluorescence emission, which suggests that positive charge on the thioFlavin T molecule has a role in its micelle formation that then bind the amyloids fibril.
770 citations
TL;DR: The kinetic treatment of reactions in micellar systems can be accomplished by considering them as microheterogeneous two-phase systems, and both nonpolar and polar reagents can be solubilized.
Abstract: The notion of "green chemistry " has encouraged even synthetic organic chemists to include water as a solvent. Incredible selectivities and activities can be achieved through the addition of amphiphiles with a defined structure. The morphology of supramolecular assemblies or associates formed by surfactants vary according to the temperature and concentration. As a rule, reactions are typically conducted using simple spherical aggregates, that is, micelles in the nanometer range. The strong polarity gradient present between the hydrophilic surface and the hydrophobic core of the micelle means that both nonpolar and polar reagents can be solubilized. This solubilization results in reactants becoming more concentrated within the micelle than in the surrounding water phase and leads to an acceleration of the reaction and causes selective effects. The kinetic treatment of reactions in micellar systems can be accomplished by considering them as microheterogeneous two-phase systems.
725 citations
TL;DR: In this article, the critical micelle concentration (CMC) of micellar electrokinetic chromatography (MEKC) was determined by means of three different methods: MEKC, spectrophotometry, and conductometry.
323 citations
TL;DR: In this article, the aggregation behavior of pure cationic surfactants (quaternary salts) in water has been studied by electrical conductivity (at 293.15-333.15 K), surface tension, dye solubilization and viscosity measurements.
306 citations
TL;DR: The observations suggest that the formation of gold nanoparticles from AuCl4- comprises three main steps: reduction of metal ions by block copolymer in solution, absorption of blockCopolymer on gold clusters and reduction ofMetal ions on the surface of these gold clusters, and growth of metal particles stabilized by block Copolymers.
Abstract: Spontaneous formation and efficient stabilization of gold nanoparticles with an average diameter of 7∼20 nm from hydrogen tetrachloroaureate(III) hydrate (HAuCl4·3H2O) were achieved in air-saturated aqueous poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) block copolymer solutions at ambient temperature in the absence of any other reducing agent. The particle formation mechanism is considered here on the basis of the block copolymer concentration dependence of absorption spectra, the time dependence (kinetics) of AuCl4- reduction, and the block copolymer concentration dependence of particle size. The effects of block copolymer characteristics such as molecular weight (MW), PEO block length, PPO block length, and critical micelle concentration (cmc) are explored by examining several PEO−PPO−PEO block copolymers. Our observations suggest that the formation of gold nanoparticles from AuCl4- comprises three main steps: (1) reduction of metal ions by block copolymer in solution, (...
287 citations
TL;DR: The results strongly support the contention that asphaltenes in toluene can be treated roughly within the micelle framework, although asphatenes may exhibit small levels of aggregation (dimers, etc.) below their CNAC.
Abstract: Asphaltenes are known to be interfacially active in many circumstances such as at toluene−water interfaces. Furthermore, the term micelle has been used to describe the primary aggregation of asphaltenes in good solvents such as toluene. Nevertheless, there has been significant uncertainty regarding the critical micelle concentration (CMC) of asphaltenes and even whether the micelle concept is appropriate for asphaltenes. To avoid semantic debates we introduce the terminology critical nanoaggregate concentration (CNAC) for asphaltenes. In this report, we investigate asphaltenes and standard surfactants using high-Q, ultrasonic spectroscopy in both aqueous and organic solvents. As expected, standard surfactants are shown to exhibit a sharp break in sonic velocity versus concentration at known CMCs. To prove our methods, we measured known surfactants with CMCs in the range from 0.010 g/L to 2.3 g/L in agreement with the literature. Using density determinations, we obtain micelle compressibilities consistent ...
254 citations
TL;DR: A novel amphiphilic biodegradable cationic hyperbranched poly(ethylene glycol)-polyethylenimine-poly(gamma-benzyl L-glutamate) block copolymer was successfully synthesized by ring-opening polymerization (ROP) of N-carboxyanhydride of gamma-benZyl-L- glutamate with PEG-PEI as a macroinitiator.
213 citations
TL;DR: The detailed interfacial adsorption and micellization behavior of pure and mixed alkyltrimethylammonium bromides were studied using tensiometric, conductometric, fluorimetric, viscometric, and calorimetric methods and the critical micellar concentration (CMC) was determined.
Abstract: The detailed interfacial adsorption and micellization behavior of pure and mixed alkyltrimethylammonium bromides (ATABs: C10-, C12-, C14-, and C16TAB) were studied using tensiometric, conductometric, fluorimetric, viscometric, and calorimetric methods. The critical micellar concentration (CMC), thermodynamics of adsorption and micellization, counterion binding, aggregation number, and micellar polarity were determined. It was observed that the studied 1:1 molar mixtures of C10−C12TAB, C10−C14TAB, and C10−C16TAB, and the mixtures C12−C14TAB and C12−C16TAB at different mole ratios produced two CMCs that were supported by the conductometric, calorimetric and viscometric methods. Compared to the first micelle, the second micelle condensed more counterions and produced a higher aggregation number, but their interior polarity states were the same. The surface excess, area minimum of the ATABs at the CMC and Gibbs free energy of adsorption were evaluated and compared. The ideality/nonideality states of the mixe...
188 citations
TL;DR: In this article, the critical micelle concentration (cmc) and degree of ionization (β) of the micelles were determined from the conductivity measurements at different temperatures, and they were analyzed in comparison with the results of DTAB in terms of effect of counter ion and increase in alkyl chain.
188 citations
TL;DR: In the H2O/FeCl3/AOT/apolar solvent system, the aqueous FeCl3 solution played a role in increasing the ionic strength and decreasing the second critical micelle concentration of AOT, and AOT reverse cylindrical micelles could be spontaneously formed in an apolar solvent.
Abstract: Polypyrrole (PPy) nanotubes were readily fabricated through chemical oxidation polymerization in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse (water-in-oil) emulsions. The reverse cylindrical micelle phase was characterized, and the key factors affecting the formation of PPy nanotubes were systematically inspected. AOT reverse cylindrical micelles were prepared via a cooperative interaction between an aqueous FeCl3 solution and AOT in an apolar solvent. In the H2O/FeCl3/AOT/apolar solvent system, the aqueous FeCl3 solution played a role in increasing the ionic strength and decreasing the second critical micelle concentration of AOT. As a result, AOT reverse cylindrical micelles could be spontaneously formed in an apolar solvent. In addition, iron cations were adsorbed to the anionic AOT headgroups that were capable of extracting metal cations from the aqueous core. Under these conditions, the addition of pyrrole monomer resulted in the chemical oxidation polymerization of the corresponding monome...
167 citations
TL;DR: In this article, the effects of a surfactant additive on the formation of a clathrate hydrate in a quiescent guest-gas/liquid-water system were investigated.
TL;DR: The results have been analyzed in terms of the equations of Clint, Motomura, Rosen, Rubingh, Blankschtein et al. for justification of the experimental cmc, determination of micellar composition parameters, quantification of interaction among the mixed micelle components, and estimation of their activity coefficients.
Abstract: Mixed micelles formed with cetyl pyridinium chloride (CPC), cetyl trimethylammonium bromide (CTAB), and polyoxyethylene (10) cetyl ether (Brij-56) mixed in different combinations in aqueous medium have been studied in detail by tensiometric, conductometric, calorimetric, spectrophotometric, and fluorimetric techniques. Different physicochemical properties such as critical micellar concentration (cmc), micellar dissociation, energetic parameters (free energy, enthalpy, and entropy) of micellization, interfacial adsorption, and micellar aggregation number have been determined. The results have been analyzed in terms of the equations of Clint, Motomura, Rosen, Rubingh, Blankschtein et al., and Rubingh and Holland for justification of the experimental cmc, determination of micellar composition parameters, quantification of interaction among the mixed micelle components, and estimation of their activity coefficients.
TL;DR: Even though molecular weights and compositions of PID chains were equivalent except for terminal groups, micelles having the outermost surface phenyl groups exhibited drastically lower phase transition temperature shifts, especially for micells with low molecular weight PID chains.
TL;DR: The results of this study provide information that may lead to the rational design of chitosan-based ingredients or products with specific nutritional and functional characteristics, for example, cholesterol lowering.
Abstract: Chitosan is a cationic biopolymer that has many potential applications in the food industry because of its unique nutritional and physicochemical properties. Many of these properties depend on its ability to interact with anionic surface-active molecules, such as surfactants, phospholipids, and bile acids. The purpose of this study was to examine the influence of pH (3 and 7), ionic strength (0-200 mM NaCl), and temperature (10-50 degrees C) on the interactions between a model anionic surfactant (sodium dodecyl sulfate, SDS) and chitosan using isothermal titration calorimetry, selective surfactant electrode, and turbidity measurements. At pH 3 and 30 degrees C, SDS bound strongly to chitosan to form an insoluble complex that contained about 4-5 mmol of SDS/1 g of chitosan at saturation. When SDS and chitosan were mixed at pH 7 they did not interact strongly, presumably because the biopolymer had lost most of its positive charge at this pH. However, when SDS and chitosan were mixed at pH 3 and then the solution was adjusted to pH 7, the SDS remained bound to the chitosan. The presence of NaCl (0-200 mM) in the solutions decreased the critical micelle concentration (cmc) of SDS (in both the absence and the presence of chitosan) but had little influence on the amount of SDS bound to chitosan at saturation. The cmc of SDS and the amount of SDS bound to the chitosan at saturation were largely independent of the holding temperature (10-40 degrees C). Nevertheless, the enthalpy changes associated with micelle dissociation were highly temperature-dependent, indicating the importance of hydrophobic interactions, whereas the enthalpy changes associated with SDS-chitosan binding were almost temperature-independent, indicating the dominant contribution of electrostatic interactions. This study provides information that may lead to the rational design of chitosan-based ingredients or products with specific nutritional and functional characteristics, for example, cholesterol lowering.
TL;DR: In this article, the effect of liquid properties (surfactants) on bubble generation phenomenon, interfacial area and liquid-side mass transfer coefficient was investigated, and the results showed that the presence of surfactants affects the bubble generation process and thus the surface coverage ratio at equilibrium.
TL;DR: In this article, the effect of added salt NaCl and NaBr on micellization and structure of cetylpyridinium chloride (CPyCl) micelles was investigated.
TL;DR: SANS results show the increase of inter-micellar interaction due to the increase in temperature/salt concentration; this is supported by viscosity data.
TL;DR: Experimental results suggested that the nanoparticles prepared from CMPC block copolymers could be a good candidate for injectable drug delivery carrier.
TL;DR: Although there are no significant interactions between micelle and protein, the properties of the micelle as a delivery vehicle may be strongly influenced by protein-drug interactions.
TL;DR: Experimental data support the model, since above 17.7 microM the time of half-aggregation is independent of peptide concentration, and the overall reaction of the conversion of monomer peptide into fibril can be treated as an apparent first-order reaction.
Abstract: Alzheimer's disease (AD) is characterized by the deposition of fibrillar deposits formed by the amyloid beta (Abeta) peptide. The most widely accepted model of fibrillogenesis of Abeta affirms that fibrillogenesis occurs in two distinct stages, nucleation and elongation. A modification of the model includes the formation of micelles. We have demonstrated with accurate experimental determinations the existence of aggregates with micellar properties (namely, the critical micellar concentration, CMC, and aggregation number). Values of the CMC were obtained by analysis of surface tension (17.5 microM) and changes in the fluorescence of pyrene (17.6 microM), respectively. The average aggregation number determined by fluorescence quenching was 25, and it was independent of peptide concentration. The presence of micelles implies that above the CMC all excess peptide is incorporated into micelles, and consequently, the monomer concentration is kept almost constant. Thus, micelles act as a peptide reservoir. Micelles are located on-pathway, since they serves as nucleation centers. Experimental data support the model, since above 17.7 microM the time of half-aggregation is independent of peptide concentration, and the overall reaction of the conversion of monomer peptide into fibril can be treated as an apparent first-order reaction.
TL;DR: In this paper, the ability of new synthesized non ionic surfactants (I and II) to protect carbon steel in acid chloride solution was investigated using potentiostatic polarization, open circuit potential, weight loss and surface tension measurements.
TL;DR: In this paper, critical micelle concentrations of several surfactants in water have been determined by conductivity measurements under hydrate-forming conditions (2 −C; 40 −bar methane) and under the same conditions with nitrogen.
TL;DR: In this article, the effectiveness of 1-dodecyl-4methoxy pyridinium bromide as corrosion inhibitor for mild steel in 2-M HCl solution was investigated.
Journal Article•
TL;DR: The maximum hemolytic effect of synthetic surfactants was more than that of the biosurfactant produced by B. subtilis ATCC 6633, and would be considered a suitable surface-active agent due to low toxicity to the membrane.
Abstract: Bacillus subtilis ATCC 6633 was grown in BHIB medium supplemented with Mn2+ for 96 h at 37 degrees C in a shaker incubator. After removing the microbial biomass, a lipopeptide biosurfactant was extracted from the supernatant. Its structure was established by chemical and spectroscopy methods. The structure was confirmed by physical properties, such as Hydrophile-Lipophile Balance (HLB), surface activity and erythrocyte hemolytic capacity. The critical micelle concentration (cmc) and erythrocyte hemolytic capacity of the biosurfactant were compared to those of surfactants such as SDS, BC (benzalkonium chloride), TTAB (tetradecyltrimethylammonium bromide) and HTAB (hexadecyltrimethylammonium bromide). The maximum hemolytic effect for all surfactants mentioned was observed at concentrations above cmc. The maximum hemolytic effect of synthetic surfactants was more than that of the biosurfactant produced by B. subtilis ATCC 6633. Therefore, biosurfactant would be considered a suitable surface-active agent due to low toxicity to the membrane.
15 Jun 2005
TL;DR: The results show that the microenvironment of the spin probe in the C16TAX surfactant micelles depends strongly on the binding of the counterion.
Abstract: Both thermodynamic and microenvironmental properties of the micelles for a series of cationic surfactants hexadecyltrimethylammonium (C16TAX) with different counterions, F−, Cl−, Br−, NO−3, and ½SO2−4, have been studied. Critical micelle concentration (CMC), degree of micelle ionization ( α ) , and enthalpy of micellization ( Δ H mic ) have been obtained by conductivity measurements and isothermal titration microcalorimetry. Both the CMC and the α increase in the order SO2−4 Δ H mic becomes less negative through the sequence NO−3 ( Δ G mic ) and entropies of micellization ( Δ S mic ) have been calculated from the values of Δ H mic , CMC, and α and can be rationalized in terms of the Hofmeister series. The variations in Δ H mic and Δ S mic have been compared with those for the corresponding series of gemini surfactants. Electron spin resonance has been used to assess the micropolarity and the microviscosity of the micelles. The results show that the microenvironment of the spin probe in the C16TAX surfactant micelles depends strongly on the binding of the counterion.
TL;DR: In this article, the effect of glycerol on the micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and of the ethoxylated nonionic surfactants Brij 58 has been investigated by various experimental techniques.
TL;DR: The critical micelle concentration of amphiphilic triblock copolymers in aqueous solution was determined by fluorescence spectroscopy using 9-chloromethyl anthracene as fluorescence probe and X-ray powder diffraction spectra showed that model drugs were molecularly dispersed in the core.
TL;DR: Nanocrystalline calcium phosphate based inorganic, hydroxyapatite (HAp), was synthesized using the dodecyl phosphate micelle system and showed between 97 and 98% theoretical density of phase-pure HAp and promoted cell-material interaction when cytotoxicity tests were performed.
Abstract: Nanocrystalline calcium phosphate based inorganic, hydroxyapatite (HAp), was synthesized using the dodecyl phosphate micelle system. The surfactant concentration during synthesis played an important role on the final properties of these HAp nanoparticles. A surfactant concentration close to the critical micelle concentration produced the nanoparticles with the highest surface area, with porous less agglomerated morphology. Compacts made of these nanopowders showed between 97 and 98% theoretical density of phase-pure HAp and promoted cell-material interaction when cytotoxicity tests were performed.
TL;DR: In this article, the adsorption isotherms of an anionic surfactant, NaDBS and a non-ionic, Triton X-100 (TX-100) have been studied on cellulose surfaces with and without the presence of electrolytes.
TL;DR: In this paper, the solubilization of polycyclic aromatic hydrocarbons (PAHs) by an anionic-nonionic mixed surfactant, sodium dodecyl sulfate (SDS) with Triton X-405 (TX405), was studied from measurements of the maximum additive concentration (MAC), the micelle-water partition coefficient (Kmc), and the critical micelle concentration (CMC).