Investigation of SDS, DTAB and CTAB micelle microviscosities by electron spin resonance

Electron spin resonance spectroscopy (ESR) of the nitroxide labelled fatty acid probes (5-, 16-doxyl stearic acid) was used to monitor the micelle microviscosity of three surfactants at various concentrations in aqueous solution: sodium dodecyl sulphate (SDS), dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB). At low surfactant concentration, there is no micelle, the ESR probe is dissolved in water/surfactant homogeneous phase and gives his microviscosity. At higher surfactant concentration, an abrupt increase in microviscosity indicates the apparition of micelles and, the solubilization of the probes in micelles. The microviscosity of the three surfactants, in a large surfactant range, was obtained as well as the critical micelle concentration (CMC). The microviscosity increased slightly with the increase in surfactant concentration. Phosphate buffer lowered the CMC value and generally increased the microviscosity.     

Physicochemical properties of mixed surfacant systems: sodium dodecyl benzene sulfonate with triton X 100

The physicochemical properties of a mixed surfactant system were studied under various conditions. The surfactants were anionic sodium dodecyl benzene sulfonate and nonionic Triton X 100. Variation of specific conductivity with concentration was used to determine the critical micelle concentration of anionic as well as the mixed surfactants. Iodine solubilization method was used to determine the CMC of the nonionic surfactant. The interaction parameter between the surfactant molecules were calculated. The wetting, foaming and detergent properties of mixed surfactant systems were studied. The variation of contact angle of the solution with teflon surface as a function of surfactant concentration was found to be a reasonably good method to determine the critical micelle concentration. Viscosity and cloud points were also determined. All these quantities are discussed. Received: 14 January 1998 Accepted: 11 June 1998     

Effects of Spacer Chain Length and Additives on Solution Properties of Cationic Gemini Surfactant

The critical micelle concentration (CMC) has been determined for the gemini surfactant trimethylene-1,3-bis(dodecyldimethyl ammonium bromide)12-s-12,2Br^?1 by means of electricity conductivity measurements. For the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, geminis have CMC values well below those of conventional single-chain cationic surfactants. The CMC of 12-3-12 reduces with the addition of n-alcohol except ethanol and with the increase of n-alcohol chain length as well as increase of concentration of n-butanol and sodium chloride. Steady-state fluorescence quenching technology has been employed to study the aggregation number of micelle, which increases with increase in the length of n-alcohol. The Kraft temperature measurements also indicate that the stability of solid surfactant hydrate decreases along with the improvement of concentration of n-butanol and sodium chloride.     

Premicellar and micelle formation behavior of dye surfactant ion pairs in aqueous solutions: deprotonation of dye in ion pair micelles

The premicellar and micelle formation behavior of dye surfactant ion pairs in aqueous solutions monitored by surface tension and spectroscopic measurements has been described. The measurements have been made for three anionic sulfonephthalein dyes and cationic surfactants of different chain lengths, head groups, and counterions. The observations have been attributed to the formation of closely packed dye surfactant ion pairs which is similar to nonionic surfactants in very dilute concentrations of the surfactant. These ion pairs dominate in the monolayer at the air-water interface of the aqueous dye surfactant solutions below the CMC of the pure surfactant. It has been shown that the dye in the ion pair deprotonates on micelle formation by the ion pair surfactants at near CMC but submicellar surfactant concentrations. The results of an equilibrium study at varying pH agree with the model of deprotonated 1:1 dye-surfactant ion pair formation in the near CMC submicellar solutions. At concentrations above the CMC of the cationic surfactant the dye is solubilized in normal micelles and the monolayer at the air-water interface consists of the cationic surfactant alone even in the presence of the dyes.     

Effect of Sodium Barbital on the Physico‐chemical Properties of Surfactants with Different Charges

The effects of sodium barbital (SB) on the solubility of different kinds of surfactants viz., CTAB (cationic head group), SDS (anionic head group) and Triton X‐100 (non ionic head group) in solution phase as well as their first and second critical micelle concentrations (CMC1 and CMC2), the change in Kraft temperatures (T_K) and cloud points (CP) have been studied. Furthermore, the article reports SB‐surfactant interaction study, which is application oriented and highlights the underlying physico‐chemical aspects of the system through florescence and conductivity measurements. The results show that the solubility of CTAB and Triton X‐100 increases with the addition of SB, and that of SDS increases in the presence of small amounts of SB and decreases in the presence of large amounts of SB. With the increasing SB concentration, the CMC of CTAB and CMC1 of Triton X‐100 both increase, while the CMC of SDS decreases, and the CMC2 of Triton X‐100 has no obvious change. The addition of SB decreases the T_K of CTAB sharply, but it increases the T_K of SDS and the CP of Triton X‐100. The different effects of SB on the physico‐chemical properties of differently charged surfactants may be related to its different interactions with the surfactants.     

Interaction of flavonoids within organized molecular assemblies of anionic surfactant

The interaction of various flavonoids (compounds having C6-C3-C6 configuration) with sodium dodecyl sulfate (SDS) an anionic surfactant was studied through absorption spectroscopy as a function of the concentration of surfactant above and below the critical micelle concentration (CMC) of the surfactant. A mechanism was proposed for the interaction between these flavonoids and anionic surfactants. The approximate number of additive molecules (flavonoids) incorporated per micelle was estimated at a particular concentration of SDS. Incorporation of additive in micelles shifts the UV absorption bands towards higher wavelengths of different magnitude. The spectral shift also depends upon the nature of the surfactant head group. The absorption spectra of the flavonoids in aqueous solution and in methanol are also reported.     

The solubility of ethane, propane, and carbon dioxide in aqueous solutions of sodium cumene sulfonate

Measurements have been made to determine the solubilities of ethane, C2H6, propane, C3H8, and carbon dioxide, CO2, in aqueous solutions of sodium cumene sulfonate (NaCS) at 25 degrees C. The solubilities measured for each gas satisfy Henry's law at all concentrations of NaCS. The solubilities of C2H6 and C3H8 exhibit quite similar behavior with respect to added NaCS. The solubilities of these two gases are very low in pure water and are found to be nearly independent of NaCS concentration over a concentration range of 0-0.4 mol NaCS/kg H2O. At intermediate concentrations of NaCS, the solubilities of C2H6 and C3H8 exhibit a gradual increase with added NaCS concentrations ranging from 0.4 to 2.0 mol NaCS/kg H2O. At NaCS concentrations greater than 2.0 mol NaCS/kg H2O, the solubilities of these two gases increase with added NaCS in an approximately linear manner, with the solubility of C3H8 increasing more rapidly than that for C2H6 (by a factor of approximately 2.5). CO2 is much more soluble in pure water than the hydrocarbon gases and exhibits markedly different behavior with respect to added NaCS. The solubility of CO2 decreases with added NaCS over a concentration range of 0-0.9 mol NaCS/kg H2O, passes through a minimum at a concentration of approximately 1.0 mol NaCS/kg H2O, and then increases with added NaCS at higher NaCS concentrations in a manner similar to that observed with C2H6 and C3H8. The trends in solubility observed for these three gases dissolved in aqueous solutions of NaCS resemble those found previously with aqueous solutions of ordinary surfactants. The solubility data measured for these three gases can be interpreted surprisingly well in terms of the mass-action model for micellization, in which salting-out effects due to monomer salt ions suppress gas solubility at low NaCS concentrations and gas solubilization by small micelles of NaCS acts to enhance gas solubility at the higher NaCS concentrations.     

Unique incorporation behavior of amino acid-type surfactant into phospholipid vesicle membrane

The incorporation behavior of some anionic surfactants, including amino acid-type surfactants, on phospholipid vesicles was investigated. This was done by measuring the release of a vesicle-entrapped fluorescence probe and the scattered light intensities of vesicle particles in the surfactant solution as a function of surfactant concentration and time. Sodium dodecyl sulfate, sodium dodecanesulfonate, sodium dodecanoyl sarcosinate, and sodium dodecanoyl glutamate were employed in this study. All surfactants ruptured the phospholipid vesicle at around each critical micelle concentration by mixed micelle formation with phospholipid. While leakage of the fluorescence probe took place at a very low concentration in the sulfate- or sulfonate-type surfactant systems, it occurred at the concentration just below the CMC in the amino acid-type surfactant systems. Kinetic analysis of the release of the probe from the vesicles showed that the former surfactants adsorbed independently and homogeneously onto the phospholipid vesicles, while the latter surfactants were cooperatively incorporated.     

Synergism and Physicochemical Properties of Anionic/Amphoteric Surfactant Mixtures with Nonionic Surfactant of Amine Oxide Type

The physicochemical properties of initial formulation, that is anionic/amphoteric surfactants mixture SLES/AOS/CAB (sodium lauryl ether sulfate (SLES), α-olefin sulfonates (AOS) and cocamidopropyl betaine (CAB) at ratio 80 : 15 : 5) with nonionic surfactant of amine oxide type (lauramine oxide (AO)) in various concentration (1–5%) were studied. To characterize the surfactants mixture, the critical micelle concentration (CMC), surface tension (γ), foam volume, biodegradability and irritability were determined. This study showed that adding of AO in those mixtures lowered both γ and CMC as well as enhanced SLES/AOS/CAB foaming properties, but did not significantly affect biodegradability and irritability of initial formulation. Moreover, an increase in AO concentration has a meaningful synergistic effect on the initial formulation properties. All those results indicates that a nonionic surfactant of amine oxide type significantly improves the performance of anionic/amphoteric mixed micelle systems, and because of that anionic/amphoteric/nonionic mixture can be used in considerably lower concentrations as a cleaning formulation.

     

A calorimetric study of three long-chain ionic surfactants

Differential enthalpies of solution in water of crystalline sodium dodecyl sulphate (SDS), sodium p-octylbenzenesulphonate (SOBS), and hexadecyltrimethylammonium bromide (CTAB) have been measured as a function of concentration at temperatures between 25 and 50 °C. The concentration change was small in the experiments and the results give a good approximation to the partial molar enthalpy content of the surfactant in the monomer and micellar states relative to the crystalline state. The enthalpies of dissolution to give monomers showed a strong, linear increase with temperature for SDS and SOBS and a nearly linear increase for CTAB, while the enthalpy of dissolution to give micelles was constant between 25 and 50 °C for the first two surfactants and only slowly increased for CTAB. Partial molar heat capacities were derived for monomeric and micellar SDS and SOBS. The large positive partial molar heat capacities of the monomeric surfactants are characteristic for hydrophobic solutes and the large heat capacity change for micelle formation arises from the loss of hydrophobic hydration in the formation of micelles.Results of microtitration experiments at 25 ° C show that the micelle formation of CTAB is not a simple aggregation process, but indicate a secondary process taking place closely after the critical micelle concentration (CMC).     

Binary mixed micelles of chiral sodium undecenyl leucinate and achiral sodium undecenyl sulfate: I. Characterization and application as pseudostationary phases in micellar electrokinetic chromatography

Sodium 10-undecenyl sulfate (SUS), sodium 10-undecenyl leucinate (SUL) and their five different mixed micelles at varied percent mole ratios were prepared. The critical micelle concentration (CMC), C₂₀, γ_CMC, partial specific volume, methylene group selectivity, mobilities and elution window were determined using a variety of analytical techniques. These surfactant systems were then evaluated as novel pseudostationary phases in micellar electrokinetic chromatography (MEKC). As a commonly used pseudostationary phase in MEKC, sodium dodecyl sulfate (SDS) was also evaluated. The CMC values of SUS and SUL were found to be 26 and 16 mM, respectively, whereas the CMC of mixed surfactants was found to be very similar to that of SUL. The C₂₀ values decreased dramatically as the concentration of SUL is increased in the mixed micelle. An increase in SUL content gradually increased the methylene group selectivity making the binary mixed surfactants more hydrophobic. Linear solvation energy relationships (LSERs) and free energy of transfer studies were also applied to predict the selectivity differences between the surfactant systems. The cohesiveness and the hydrogen bond acidic character of the surfactant systems were found to have the most significant influence on selectivity and MEKC retention. The SUS and SDS showed the strongest while SUL showed the weakest hydrogen bond donating capacity. The basicity, interaction with n and π-electrons of the solute and dipolarity/polarizability were the least significant factors in LSER model for the surfactant systems studied. Free energies of transfer of selected functional groups in each surfactant systems were also calculated and found to be in good agreement with the LSER data.     

Determination of critical micelle concentrations of ionic and nonionic surfactants based on relative viscosity measurements by capillary electrophoresis

The critical micelle concentration (CMC) can be obtained by measuring the distinct physical properties of surfactant molecules in the monomeric and micellar states. In this study, two linear increments of relative viscosity with distinct slopes were obtained when increasing surfactant concentrations from dilute solution to above the CMC, which was then determined by the intersection of the two linear extrapolations. Using a capillary electrophoresis (CE) instrument and Poiseuille’s law, the viscosities of surfactants at a series of concentrations covering the monomeric and micellar regions could be obtained by measuring the hydrodynamic flow rates of the corresponding surfactant solutions. We applied this method to determine the CMC values of various types of surfactants including anionic, cationic, zwitterionic, and nonionic surfactants. The resulting CMC values were all in good agreement with those reported in literature. Using this method, the multiple-stage micellization process of a short-chain surfactant was revealed. We have also demonstrated that the CE-based viscometer was applicable to the study of CMC variation caused by organic or electrolyte additives.     

Microstructure of un-neutralized hydrophobically modified alkali-soluble emulsion latex in different surfactant solutions

At low pH conditions and in the presence of anionic, cationic, and nonionic surfactants, hydrophobically modified alkali-soluble emulsions (HASE) exhibit pronounced interaction that results in the solubilization of the latex. The interaction between HASE latex and surfactant was studied using various techniques, such as light transmittance, isothermal titration calorimetry, laser light scattering, and electrophoresis. For anionic surfactant, noncooperative hydrophobic binding dominates the interaction at concentrations lower than the critical aggregation concentration (CAC) (C < CAC). However, cooperative hydrophobic binding controls the formation of mixed micelles at high surfactant concentrations (C > or = CAC), where the cloudy solution becomes clear. For cross-linked HASE latex, anionic surfactant binds only noncooperatively to the latex and causes it to swell. For cationic surfactant, electrostatic interaction occurs at very low surfactant concentrations, resulting in phase separation. With further increase in surfactant concentration, noncooperative hydrophobic and cooperative hydrophobic interactions dominate the binding at low and high surfactant concentrations, respectively. For anionic and cationic surfactant systems, the CAC is lower than the critical micelle concentration (CMC) of surfactants in water. In addition, counterion condensation plays an important role during the binding interaction between HASE latex and ionic surfactants. In the case of nonionic surfactants, free surfactant micelles are formed in solution due to their relatively low CMC values, and HASE latexes are directly solubilized into the micellar core of nonionic surfactants.     

Diffusion of sodium dodecyl sulfate micelles in agarose gels

The gradient diffusion of ionic sodium dodecyl sulfate micelles in agarose gel was investigated at moderate concentrations above the CMC. Of particular interest were the effects of micelle, gel, and sodium chloride concentration on the micelle diffusivity. Holographic interferometry was used to measure the gradient diffusion coefficient at three sodium chloride concentrations (0, 0.03, 0.10 M), three gel concentrations (0, 1, 2 wt%), and several surfactant concentrations. Time-resolved fluorescence quenching was used to measure aggregation numbers both in solution and gel. The micelle diffusivity increased linearly with surfactant concentration at the two larger sodium chloride concentrations and all gel concentrations. In general, the strength of this effect increased with decreasing sodium chloride concentration and increased with gel concentration. This behavior is evidence of decreasing micelle-micelle electrostatic interactions with increasing sodium chloride concentrations, and increasing excluded volume effects and hydrodynamic screening with increasing gel concentration, respectively. The only exception was at 0.1M sodium chloride and 2 wt% agarose, which showed a slight reduction in the slope compared to 1 wt% agarose. It was found that the concentration effect is quite strong for charged solutes: at a NaCl concentration of 0.03 M in a 2% agarose gel, in a solution with 3% SDS micelles by volume, the micelle diffusion coefficient is doubled relative to its value in the same gel at infinite dilution. The extrapolated, infinite-dilution diffusion coefficients and the rate at which the micelle diffusivity increased with surfactant concentration were compared with predictions of previously published theories in which the micelles are treated as charged, colloidal spheres and the gel as a Brinkman medium. The experimental data and theoretical predictions were in good agreement.     

Hydrotropic Behavior of Sodium Salicylate in Presence of Additives

It is well known that, like surfactants aggregating at a certain concentration (called critical micelle concentration, CMC), hydrotropes also have minimum hydrotrope concentration (MHC). However, unlike surfactant CMC, this MHC value is usually very high, thereby reducing their application. In this paper we report the results of conductivity and viscosity measurements with a well known hydrotrope sodium salicylate (NaSal) solutions in presence and absence of additives (propanol, PrOH; butanol, BuOH; pentanol, PeOH and tetrabutylammonium bromide, Bu₄NBr). We have found that MHC value of NaSal decreases in presence of additives. Alcohols increase the hydrophobic interactions and decrease the MHC while Bu₄NBr, in addition to ameliorating the hydrophobic interactions, reduces the charge on head groups and MHC decreases more steeply in its presence. Increased solubility of riboflavin in NaSal containing the above additives corroborates the results.     

Adsorption and micelle formation of alkylammonium chloride-alkyltrimethylammonium chloride mixtures

The surface tension of the aqueous solutions of binary cationic surfactant mixtures of (1) dodecylammnonium chloride (DAC)-tetradecyltrimethylammonium chloride (TTAC), (2) decylammonium chloride (DeAC)-dodecyltrimethylammonium chloride (DTAC), and (3) DAC-DTAC was measured as a function of the total molality and composition of surfactants at 298.15 K. The compositions of surfactants in the adsorbed film and micelle were evaluated and the phase diagram of adsorption and that of micelle formation were constructed. Furthermore the excess Gibbs energies of adsorption and micelle formation were calculated to estimate the deviation from the corresponding ideal mixing. It was found that the surface and micelle are enriched in trimethylammonium salts in (1) and (2), while in ammonium salt in (3) compared to the bulk solution. On the other hand, the micelle is enriched in trimethylammonium salts compared to the surface at the critical micelle concentration (CMC) in all the systems. The miscibility of the surfactants was clarified from the standpoints of the structure of the head group and of the matching between the size of polar head group of surfactants and the difference in hydrocarbon chain length.     

The Surface and Thermodynamic Properties of Ethoxylated Sodium Monoalkyl Sulfosuccinate Surfactants

A series of ethoxylated sodium monooctyl sulfosuccinates [E(n)SMOSS] and ethoxylated sodium monolauryl sulfosuccinates [E(n)SMLSS] have different units of ethylene oxide (n = 9, 14, 23) were synthesized. The surface and thermodynamic properties of these surfactants have been compared with sodium dioctyl sulfosuccinate surfactant (SDOSS) as a commonly used surfactant. The surface tension measurements at 25, 35, 45, and 55°C were used to determine of the critical micelle concentration (CMC) and surface active properties of these surfactants. The effect of the ethylene oxide (EO) unit and the alkyl chain length on the surface properties for the prepared surfactants was studied. The results show that the ethoxylated sodium monoalkyl sulfosuccinates generally have lower values of CMC than that of sodium dioctyl sulfosuccinate. The values of surface active parameters indicate that the ethoxylated sodium monooctyl sulfosuccinates and ethoxylated sodium monolauryl sulfosuccinates surfactants have adsorption properties better than the sodium dioctyl sulfosuccinate surfactant as a resulted presence of ethylene oxide in molecules of the prepared surfactants. The thermodynamic parameters show that the (EO) unites in the chemical structure of ethoxylated sodium monoalkyl sulfosuccinate surfactants improve their micellization and adsorption properties.     

壬基酚聚氧乙烯醚在油相中的CMCo及相关问题研究

对壬基酚聚氧乙烯醚在油相中的临界胶束浓度(CMC_o)及与之相关的问题进行了研究,并获得了部分CMC_o值.对CMC_o与表面活性剂自身结构的关系进行分析和数学处理后,发现CMC_o与活性物质自身结构间仍为对数关系.同时在对某些具体体系的界面张力随表面活性剂不同而发生的变化进行了详细分析,发现CMC_w和CMC_o是评价表面活性剂性能的有效工具.     

Effect of protic ionic liquids (PILs) on the formation of non-ionic dodecyl poly(ethylene oxide) surfactant self-assembly structures and the effect of these surfactants on the nanostructure of PILs

The ability of a series of non-ionic dodecyl poly(ethylene oxide) surfactants to form micelles in a variety of protic ionic liquids (PILs) was investigated using small and wide angle X-ray scattering (SAXS/WAXS). The C(12)E(n) surfactants with n = 3-8 were examined in PILs which contained either an ethyl, diethyl, triethyl, butyl, pentyl, ethanol or pentanol-ammonium cation in conjunction with either a nitrate or formate anion. The ability of the PILs to support micelles of these surfactants was highly dependent on their liquid nanostructure. The PILs containing hydroxyl groups on the cations were not nanostructured and had very low surfactant solubility (<1 wt%). The highly nanostructured PILs with butylammonium or pentylammonium cations contain large non-polar domains, and had excellent surfactant solubility, but due to the greater hydrocarbon solubility they had insufficient drive from the "solvophobic effect" to enable micelle formation. The PILs of ethylammonium nitrate (EAN), propylammonium nitrate (PAN), diethylammonium formate (DEAF) and triethylammonium formate (TEAF) had smaller non-polar domains, and all supported micelle formation below 20 wt% surfactant. The critical micelle concentration (CMC) of surfactants in EAN were two orders of magnitude greater than in water. The minimum molecular areas of the poly(ethylene oxide) head groups at the air/ionic liquid interface, A(min), were significantly larger in EAN than in water. The SAXS patterns from the micelles present in EAN fitted well to ellipsoids, whereas the micelles present in PAN fitted well to spheres. The nanostructure of select PILs was also influenced by the presence of surfactants.     

Volumetric properties of sodium perfluoroalkylcarboxylates in aqueous solutions at different temperatures

Densities and sound velocities of sodium perfluorohexanoate and sodium perfluorononanoate for different concentrations above and below the critical micelle concentration (cmc) have been obtained at different temperatures. Apparent molar volumes and compressibilities of the surfactants in the monomeric and micellar form have been estimated. The relevant results were plotted as a function of the temperature and the alkyl chain length by using previous data reported for sodium heptanoate and sodium octanoate. The expected linear behaviour in function of temperature and also alkyl chain length have been found. In order to analyze the influence of the substitution of the hydrogen by fluorine in the alkyl chain of the surfactant, the data were compared with the hydrogenated counterpart.