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1.
《Physics and Chemistry of Liquids》2012,50(3):227-238
A potentiometric technique based on surfactant ion selective electrode has been used for various cationic and anionic surfactants. The data obtained contain m 1 (surfactant monomer concentration); m 2 (free counterion concentration) and α (degree of dissociation of micelle) were used for determination of aggregation number at and above cmc (critical micelle concentration). Data fitting show a relationship between aggregation number with such parameters. The correlation equation obtained shows that size of ionic micelle vary sharply after cmc. Also, the equation obtained shows size of micelle growth with increase in counterion concentration. 相似文献
2.
Pankaj Sehgal Tami Mizuki Hidekazu Doe Reinhard Wimmer Kim Lambertsen Larsen Daniel E. Otzen 《Colloid and polymer science》2009,287(11):1243-1252
The interactions of α-cyclodextrin (α-CD) with the nonionic surfactant decanoyl-N-methyl-glucamide (Mega-10) and the zwitterionic surfactant dimethyldodecylammoniopropanesulfonate (DPS) in their mixed system have been studied using interfacial tension, fluorescence, and nuclear magnetic resonance measurements. From the plots of interfacial tension vs. log of total surfactant concentration, we have obtained values of the surface excess of surfactant, the critical micellar concentration (cmc), the standard free energy of micelle formation, and association constant of surfactant/α-CD inclusion complexes (assuming a 1:1 stoichiometry). A comparison of the K a values obtained for the interaction between α-CD and DPS and Mega-10, respectively, shows that DPS interacts stronger with α-CD than Mega-10. The experimental mixed cmc was analyzed by the pseudophase separation model and regular solution theory for the evaluation of ideality or nonideality of the mixed micelle formation. The interaction parameters in the mixed micelle and the micelle composition at different mole fractions of DPS were also computed. The fluorescence anisotropy (r) values of rhodamine B decreases with the increase of α-CD concentrations. 相似文献
3.
Two breaks have been found on the conductivity, refractive index, density and sound velocity against molality plots for aqueous solutions of dodecyldimethylbenzylammonium chloride at 25 °C, in the absence of any additive. The first break corresponds to the critical micelle concentration, cmc. The second, less distinct break, occurring in the molality range of 0.082 to 0.104 mol kg-1, in dependence on the technique applied, has been ascribed to the second critical micelle concentration, 2nd cmc, responsible for structural transitions of spherical micelles. Values of cmc and 2nd cmc have been also estimated conductometrically for tetradecyltrimethylammonium bromide and dodecylpyridinium chloride. On the basis of available conductometric data it has been shown that the 2nd cmc/cmc ratio varies in the range of 2 to 10 in dependence on the type of 1:1 ionic surfactant. It has been also shown that for a given class of surfactants, the logarithm of 2nd cmc varies linearly with the number of carbon atoms in the alkyl chain ( n= 12, 14 and 16). Both empirical regression coefficients depend upon the class of surfactants considered. 相似文献
4.
Paul Wiseman Catherine A. Kennedy D. Gerrard Marangoni Ramamurthy Palepu 《Journal of solution chemistry》1998,27(3):217-233
A family of two-headed surfactants, the disodium 4-alkyl-3-sulfonatosuccinates, has been prepared by reacting maleic anhydride with the appropriate chain-length alcohol and subsequent addition of sodium bisulfite to the corresponding monoester. The properties of the micelles formed by these compounds in aqueous solution (aggregation numbers, degrees of counterion binding, and the cmc values) have been investigated as a function of temperature and surfactant chain length using viscosity, density, and conductance measurements. The critical micelle concentrations (cmc's) and the aggregation numbers appear to indicate that, in agreement with the earlier literature on other two-headed surfactants systems, these amphiphiles have higher cmc and lower aggregation numbers when compared to single-headed surfactants of comparable chain length. In addition, viscosity B coefficients and the thermodynamic parameters of activation of viscous flow have been determined. These results are interpreted in terms of the structure-making or -breaking properties of the surfactant amphiphiles below the cmc region. Finally, the thermodynamic properties of micelle formation have been estimated from the dependence of the cmc on the absolute temperature according to the charged pseudo-phase separation model of micelle formation. All these results are discussed in terms of how the addition of the second charged surfactant headgroup alters the micellar and solution properties of two-headed surfactants vs. their single-headed counterparts. 相似文献
5.
C. Carnero Ruiz 《Colloid and polymer science》1999,277(7):701-707
The aggregation behaviour of tetradecyltrimethylammonium bromide in ethylene glycol–water mixtures across a range of temperatures
has been investigated by electrical conductivity measurements. The critical micelle concentration (cmc) and the degree of
counterion dissociation of micelles were obtained at each temperature from plots of differential conductivity, (κ/c)
T
,
P
, versus the square root of the total concentration of the surfactant. This procedure not only enables us to determine the
cmc values more precisely than the conventional method, based on plots of conductivity against total concentration of surfactant,
but also allows straightforward determination of the limiting molar conductance and the molar conductance of micellar species.
The equilibrium model of micelle formation was applied to obtain the thermodynamics parameters of micellization. Only small
differences have been observed in the standard molar Gibbs free energies of micellization over the temperature range investigated.
The enthalpy of micellization was found to be negative in all cases, and it showed a strong dependence on temperature in the
ethylene glycol poor solvent system. An enthalpy–entropy compensation effect was observed for all the systems, but whereas
the micellization of the surfactant in the solvent system with 20 wt% ethylene glycol seems to occur under the same structural
conditions as in pure water, in ethylene glycol rich mixtures the results suggest that the lower aggregation of the surfactant
is due to the minor cohesive energy of the solvent system in relation to water.
Received: 13 December 1998 Accepted in revised form: 25 February 1999 相似文献
6.
Mixed micelle formation and surface tension reduction effectiveness (γcmc) were investigated for the following systems: triethanolammonium dodecylpoly(oxyethylene)sulfate (TADPS, containing about
two ethylene oxide units)/dodecyltrimethylammonium bromide, TADPS/hexadecyltrimethylammonium bromide and TADPS/hexadecylpyridinium
chloride. For all these anionic/cationic systems, the mixed critical micelle concentration (cmc) values reflect a strong synergism
in mixed micelle formation, with βM values ranging from −13.8 to −18.3. The mixed micelle composition is mixing-ratio dependent and, for equimolar mixtures,
the mixed micelle is richer in the surfactant with the lower cmc. Precipitation is inhibited to a certain extent, thanks to
the presence of ethylene oxide groups in the anionic species. The conditions for synergism in γcmc, differently expressed in the literature, can be derived from the surface tension equations established in our previous article.
They can be conveniently described by a few characteristic constants: Γ
i
∞ (saturated Gibbs excess), K
i
(constant in the Szyszkowski equation), the cmc of the individual surfactants and the interaction parameters, βS and βM, of their mixtures. Excellent agreement between theoretically predicted and experimental results is obtained. With the increase
in surfactant chain length, the βM values decrease faster than the βS ones and this can result in the loss of synergism in γcmc.
Received: 11 June 2000 Accepted: 4 September 2000 相似文献
7.
The competitive binding of counterions to anionic dodecyl sulfate ions in aqueous solutions of cesium dodecyl sulfate (CsDS)
and sodium dodecyl sulfate (SDS) mixtures, which significantly influences the critical micelle concentration (cmc) and surface
(or interfacial) tension of surfactant solutions, was investigated. The cmc and degree of counterion binding were obtained
through electrical conductivity measurements. The curve of cmc versus the mole fraction of CsDS in the surfactant mixture
was simulated by Rubingh's equations, which enabled us to estimate the interaction parameter in micelles (W
R) based on the regular solution approximation. The curve-fitting exhibited a slightly negative value (W
R=−0.1), indicating that the mixing (SDS+CsDS) enhances micelle formation owing to a greater interaction between surfactant
molecules and counterions than in pure systems (SDS). On going from SDS, SDS:CsDS(75:25), SDS:CsDS(50:50), SDS:CsDS(25:75)
to CsDS, interfacial tension at the hexadecane/surfactant-solution interface showed a negative deviation from the mixing rule
(interaction parameter in adsorbed film W
A=−0.38), indicating the replacement of Na+ bound to anionic dodecyl sulfate by Cs+ ions owing to the stronger interaction between the Cs+ and the dodecyl sulfate ions. Droplet sizes of emulsion formed with hexadecane and aqueous dodecyl sulfate solutions were
investigated using the light scattering spectrophotometer. The higher binding capacity of Cs+, having a smaller hydrated ionic size than Na+, also resulted in a negative deviation in emulsion droplet size in mixed systems.
Received: 10 May 2000/Accepted: 11 August 2000 相似文献
8.
9.
Jose Ramos Jacqueline Forcada 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2322-2334
The objective of this work was to analyze the effects of the concentration and type of cationic surfactant on the kinetic features (instantaneous and overall conversions) and colloidal characteristics [mean particle diameter, particle size distribution (PSD), and surface charge density] in the semicontinuous seeded cationic emulsion polymerization of styrene. 2,2′‐Azobis(N,N′‐dimethyleneisobutyramidine)dihydrochloride was used as an initiator. The surfactants were dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (HDTAB). So that the evolution of some polymeric and colloidal characteristics of the synthesized latices could be followed, the overall and instantaneous conversions were defined and determined gravimetrically. The PSDs and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The surface charge density was determined by conductimetric titration. The evolution of the instantaneous conversions, the total number of particles, and the PSDs of the different reactions were related to the nucleation, growth, and coagulation processes taking place in the semicontinuous seeded emulsion polymerizations. The PSDs obtained from the reactions carried out with the emulsifier DTAB, at a concentration equal to its critical micelle concentration (cmc) and at a concentration twice its cmc, presented more and smaller particles than those obtained by the addition of HDTAB to the polymerization recipe. At lower emulsifier concentrations equal to half of the cmc, the system had lower colloidal stability with DTAB. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2322–2334, 2003 相似文献
10.
Shi‐Li Song Zhi‐Guo Hu Yu‐Hua Qian Zheng Chen Gao‐Yong Zhang 《Journal of Dispersion Science and Technology》2013,34(6):907-913
We have investigated the mixing behavoir of a pH‐mediated ternary surfactant mixture at constant ratio of dodecyldimethylamine oxide (DDAO) and Triton X‐100 (9:1). From the equilibrium surface tension measurements at different pHs, the critical micelle concentration (cmc) data were obtained as functions of the pH. Values of the cmc and composition of the micelles were predicted using the regular solution approximation. To some extent, the experimental cmc values agree with the predicted cmc. The average degree of ionization of dodecyldimethylamine oxide in the mixed surfactant systems was estimated using potentiometric titrations. The surface electric potential of the micelles (Ψo) was determined using two methods, one by hydrogen ion titration and the other by the dissociation constants of an acid‐base indicator. In a high degree of ionization of DDAO in the micelles phase (am), Ψo estimated from acid‐base indicator is much higher than that from hydrogen ion titration. In the protonated dodecyldimethylamine oxide/TX‐100 binary surfactant system, Ψo estimated from hydrogen ion titration was as high as 89 mV. The micellar aggregation numbers evaluated by the steady‐state fluorescence probe method increase with pH except at pH=5.03. At pH=5.03, the maximum micelle aggregation number was observed. 相似文献
11.
《Journal of Dispersion Science and Technology》2013,34(6):535-539
The effects of monomeric surfactants on the hydride transfer from (one electron oxidation of) methylene blue leucodye to (by) 2,5-dihydroxy-1,4-benzoquinone in aqueous solution were investigated at 25°C using a stopped-flow spectrometer. The results indicated that cationic, anionic, and zwitterionic surfactants inhibited the reaction while nonionic surfactant showed no appreciable effect on the reaction. These observations are rationalized by electrostatic factors between surfactant monomer (or micelle) and reactant with charge or the charge transfer complex of the hydride transfer reaction. Above the cmc, the effects are treated quantitatively using a kinetic model. 相似文献
12.
S.K. Mehta Bhawna K.K. Bhasin Anil Kumar 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,346(1-3):195-201
The solubilization and conformational behavior of Zein in the presence of cationic surfactant, dodecyldimethylethylammonium bromide (DDAB) have been studied. The colloidal properties of DDAB in the absence and presence of Zein have also been investigated using physico-chemical and spectroscopy methods. The surfactant appears to bind to Zein at concentrations below the critical micelle concentration (cmc) and the binding becomes weaker at concentrations above the cmc. The interaction between DDAB and Zein depends on the chemical structure and molecular parameters (conformation, molar mass, charge) of the protein. The schematic sketches of the molecular mechanisms of the complex formation between like-charged proteins and surfactants have been proposed. 相似文献
13.
A González-Pérez J. Czapkiewicz J. L. Del Castillo J. R. Rodríguez 《Colloid and polymer science》2004,282(12):1359-1364
The micellar properties of tetradecyltrimethylammonium nitrate (C14TANO3) in aqueous solutions in the temperature range of 10 to 35 °C and in aqueous solutions of benzyl alcohol (BzOH) at 25 °C were studied conductometrically. The specific conductivity data served for the evaluation of critical micelle concentration, cmc, and the degree of ionization of the micelles, , of the surfactant. From the temperature dependence of the cmc the thermodynamic parameters for micellization of C14TANO3 were calculated by applying Mullers modified equation. BzOH was found to affect strongly the cmc and values of the surfactant. The plot of the cmc/cmco ratio (where cmco is for pure water) as a function of BzOH molality, exhibits a characteristic break, which was attributed to the commencement of self-association of BzOH in aqueous solution at a molality of ca. 0.05. By applying the theoretical treatment suggested by Motomura for binary surfactant systems, the molar fraction of BzOH in the micelles at cmc, was estimated as a function of molality of the alcohol. C14TANO3 appears to be slightly more hydrophobic compared to the corresponding bromide. 相似文献
14.
Micelle formation in sodium dodecyl sulfate (SDS)–n-octanol mixtures was studied by several techniques and the results were interpreted using regular solution theory for mixed-micelle
formation. Octanol was considered as a nonionic surfactant. The composition of micelles at the critical micelle concentration
(cmc) was computed together with the interaction parameter and the activity coefficient of the components of the micelles.
The fluorescence quenching technique with pyrene was employed to obtain the SDS and octanol aggregation numbers at the cmc.
The results were in agreement with similar studies on other alcohol–SDS systems. At the cmc spherical, almost fully ionized
micelles formed, while at a higher concentration there was a transition to anisometric (probably rodlike) micelles which pushed
sodium counterions into their Stern double layer. Mixed anisometric micelles were more ionized than pure SDS micelles. When
the octanol:SDS total ratio exceeded 0.85:1, an emulsion of octanol appeared in equilibrium with the micelles.
Received: 23 December 1998 Accepted in revised form: 3 March 1999 相似文献
15.
Olanrewaju Owoyomi Grace Oluwafunmilayo Ogunlusi Omoetan Monday Olatan 《Physics and Chemistry of Liquids》2016,54(6):769-778
Effects of two anionic hydrotropes – sodium benzoate (NaBz) and sodium salicylate (NaSal) – on the mixed-micelle formation with an amino-acid-based surfactant – sodium lauroylsarcosinate (SLS) – in water were investigated by the conductometric method. Specific conductivity was measured for SLS/NaBz/water and SLS/NaSal/water systems to determine the critical micelle concentration (cmc). Using the regular solution theory for non-ideal mixing, the pairwise interaction parameter, β12, and micellar composition, χ, were estimated in the mixed micelle. The cmc values of the surfactant–hydrotropes mixtures were generally lower than those predicted from the ideal mixing theory. The β12 values are generally negative for the two systems at all mole fractions with an average value of ?2.83 for the SLS/NaBz and ?3.31 for SLS/NaSal systems, respectively, indicative of a strong attractive interaction between the SLS/NaBz and SLS/NaSal mixed micelle. The calculated thermodynamic parameters of micellisation all indicated spontaneity in mixed-micelle formation for the systems studied. 相似文献
16.
Pedro V. Verdes Elena Blanco Juan M. Ruso Gerardo Prieto Flix Sarmiento 《The Journal of chemical thermodynamics》2008,40(9):1445-1450
An investigation on the dependence of the thermodynamics of micellization of different surfactants such as sodium dodecyl sulfate (SDS), sodium octanoate (C8HONa), and sodium perfluorooctanoate (C8FONa) on the concentration of human serum albumin (HSA) has been realized. The critical micelle concentration (cmc) and ionisation degree of micellization, β, as a function of temperature (T), in solutions containing 0.125% and 0.250% in v/w of HSA, were estimated from conductivity data. From these results, the average number of surfactant monomers per protein molecule was calculated: higher values were found for C8HONa, the lowest value corresponded to SDS. For all the systems under study, electrostatic forces mainly drive the interaction between the surfactants and the proteins. Plots of cmc against temperature appear to follow the typical U-shaped curve with a minimum Tmin. Thermodynamic functions of micellization were obtained by applying the theoretical models that best fit our experimental data, showing that the addition of HSA shows different patterns depending on the surfactant and thermodynamic quantity. Changes in the protein conformation due to the adsorption of surfactant molecules have been monitored by using UV-CD spectra. Greater changes in α-helical contents correspond with the concentrations over cmc, indicating that at low concentrations surfactants act as a structure stabilizer; meanwhile they act as a destabilizer at higher concentrations. C8HONa is the most effective reducing α-helical content, SDS is the less effective content. 相似文献
17.
Yangchun Xie Tong Sun Ying Han Guangmiao Qu Ruixia Niu 《Journal of Dispersion Science and Technology》2018,39(8):1153-1159
The dentritic quaternary ammonium salt-type tetrameric surfactant (4C12tetraQ) was synthesized, and the molecular structure was confirmed by 1H NMR and FTIR. The surface activity of 4C12tetraQ was investigated by surface tension, and surface chemical parameters, such as critical micelle concentration (cmc), efficiency (pC20), effectiveness (πcmc), the surface tension value at cmc (γcmc), minimum surface area (Amin), maximum surface excess (Γmax), and cmc/C20 were obtained from the measurement results. The results show that the 4C12tetraQ surfactant has higher surface activity than the traditional monomeric surfactants (dodecyl trimethyl ammonium bromide, DTAB). The Krafft points were taken as <0°C, indicating that the synthesized tetrameric surfactants had good water solubility. Free energies of micellization and adsorption show that 4C12tetraQ display greater propensity to absorb at the interface than form micelle in the bulk of the aqueous solution, and that the two processes are spontaneous. The measurement results show that 4C12tetraQ has good emulsification power and foam performance. The corrosion efficiency was evaluated with the loss weight method in 1?mol/L HCl solution, and the results show that the 4C12tetraQ surfactant has good corrosion inhibition, and can be considered as a corrosion inhibitor. 相似文献
18.
Kinetics of reduction of the surfactant complex ions, cis‐chloro/bromo (dodecylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous solution was studied at 303, 308, and 313 K by spectrophotometry method under pseudo‐first‐order conditions, using an excess of the reductant. The second‐order rate constant remains constant below critical micelle concentration (cmc), but increases with cobalt(III) concentration above cmc, and the presence of aggregation of the complex itself alters the reaction rate. The rate of reaction was not affected by the added [H+]. Variation of ionic strength (μ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe2+ (aq) with cobalt(III) complex proceeds by the inner‐sphere mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 98–105, 2006 相似文献
19.
IntroductionCriticalmicelleconcentration (cmc)ofsurfactantsinaqueoussolutionisoneofthemostusefulparametersforcharacterizingthepropertiesofsurfactants.Overaverynarrowconcentrationrangearoundthecmctransitionsoftheexistenceofsurfactantsoccurfrommonomer ,premicel lartomicellar .Andcompanyingthesetransitions ,manyotherimportantpropertiesofsurfactantsolution ,suchassurfacetension ,interfacialtension ,conductivity ,osmoticpressure ,detergency ,emulsification ,foamingandsoon ,alsochangesharplyatthepoi… 相似文献