The Self-Association and Mixed Micellization of an Anionic Surfactant,Sodium Dodecyl Sulfate,and a Cationic Surfactant,Cetyltrimethylammonium Bromide: Conductometric,Dye Solubilization,and Surface Tension Studies

In the present study, we investigate the self-association and mixed micellization of an anionic surfactant, sodium dodecyl sulfate (SDS), and a cationic surfactant, cetyltrimethylammonium bromide (CTAB). The critical micelle concentration (CMC) of SDS, CTAB, and mixed (SDS + CTAB) surfactants was measured by electrical conductivity, dye solubilization, and surface tension measurements. The surface properties (viz., C₂₀ (the surfactant concentration required to reduce the surface tension by 20 mN/m), Π_CMC (the surface pressure at the CMC), Γ_max (maximum surface excess concentration at the air/water interface), and A_min (the minimum area per surfactant molecule at the air/water interface)) of SDS, CTAB, and (SDS + CTAB) micellar/mixed micellar systems were evaluated. The thermodynamic parameters of the micellar (SDS and CTAB), and mixed micellar (SDS + CTAB) systems were evaluated.

A schematic representation of micelles and mixed micelles.     

Self aggregation of binary mixtures of sodium dodecyl sulfate and polyoxyethylene alkyl ethers in aqueous solution

The mixed micelles of sodium dodecyl sulphate (SDS) with Brij35 and Brij 97 were studied separately by fluorescence measurement using pyrene as fluorescent probe. In the range of 0–1.0 mole fraction (X) of added SDS to Brij solutions, the cmc value of the mixed micelles varies from 0.085 to 8 mmol with Brij 35 and 0.04 to 8 mmol with Brij 97. The aggregation number also changes. A measure of the stability of mixed micelles is also presented. The interaction parameter ₁₂ and the chain–chain contribution parameter (B₁) are extracted from the analysis of the results. This parameter B₁ is related to the standard free energy change associated with the introduction of one ionic species into a nonionic micelle coupled with the release of one nonionic species from the micelle. The clouding behaviour of Brij 97 in the presence of SDS was investigated and the associated thermodynamic parameters of clouding were generated and discussed.     

Dispersity of stratum corneum in the mixed aqueous solutions of binary mixtures between N,N-dimethyldodecylamine oxide and sodium dodecyl sulfate or two terpenes

Solubilization of cholesterol, differential scanning calorimetric (DSC), nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements were performed in order to reveal the dispersion mechanisms of stratum corneum (SC) into each intact corneocytes in the following systems: (1) in the aqueous mixed solutions of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine oxide (C₁₂DMAO); (2) in the aqueous micellar solutions of C₁₂DMAO containing solubilized α-terpineol (α-T); and (3) in the aqueous micellar solutions of C₁₂DMAO containing solubilized limonene. The intercellular lamellar structure of SC was revealed to be disrupted and/or removed in all these solutions. However, considering the micellar sizes and the interaction among molecules in micelle, the dispersion mechanisms in these three systems were different each other. The three dispersion mechanisms of SC were estimated and discussed on the basis of the results of solubilization, DSC, NMR and DLS, respectively.     

十二烷基硫酸钠水溶液的动态表面吸附性质

利用MPTC型气泡压力张仪研究了十二烷基硫酸钠(SDS)溶液在不同NaCl 浓度下的动态表面吸附性质, 分析了离子型表面活性剂在表面吸附层和胶束中形成双电层结构产生表面电荷对动态表面扩散过程和胶束性质的影响. 结果表明, SDS在表面吸附过程中, 表面电荷的存在会产生5.5 kJ·mol^-1的吸附势垒(E_a), 显著降低十二烷基硫酸根离子(DS^-)的有效扩散系数(D_eff). 十二烷基硫酸根离子的有效扩散系数与自扩散系数(D)的比值(D_eff/D)仅为0.013, 这表明SDS与非离子型表面活性剂不同, 在吸附初期为混合动力控制吸附机制. 加入NaCl可以降低吸附势垒. 当加入不小于80 mmol·L^-1 NaCl后, E_a小于0.3 kJ·mol^-1, D_eff/D在0.8-1.2之间, 表现出与非离子型表面活性剂相同的扩散控制吸附机制. 同时, 通过分析SDS胶束溶液的动态表面张力获得了表征胶束解体速度的常数(k₂). 发现随着NaCl 浓度的增大, k₂减小, 表明SDS胶束表面电荷的存在会增加十二烷基硫酸根离子间的排斥力, 促进胶束解体.     

Micellization and Interaction Properties of Aqueous Solutions of Mixed Cationic and Nonionic Surfactants

The micellization process of binary surfactant mixtures containing cationic surfactants viz. dodecyl pyridinium halide (C₁₂PyX; X=Cl, Br, I), tetradecyl pyridium bromide (C₁₄PyBr), and hexadecyl pyridium halide (C₁₆PyX; X=Cl, Br) and a nonionic surfactants viz. dodecyl nonapolyethylene glycol ether (C₁₂E₉), dodecyl decapolyethylene glycol ether (C₁₂E₁₀), dodecyl dodecapolyethylene glycol ether (C₁₂E₁₂), and dodecyl pentadecapolyethylene glycol ether (C₁₂E₁₅) in water at different mole fractions (0–1) were studied by surface tension method. The composition of mixed micelles and the interaction parameter, β evaluated from the CMC data obtained by surface tension for different systems using Rubingh's theory were discussed. Activity coefficient (f₁ and f₂) of cationic surfactant (C_nPyBr)/C₁₂E_m (n=12, 14, 16 and m=10, 12, 15) mixed surfactant systems were evaluated, which shows extent of ideality of individual surfactant in mixed system. The stability factors for mixed micelles were also discussed by Maeda's approach, which was justified on the basis of steric factor due to difference in head group of nonionic surfactant.     

Micellization of sodium dodecyl sulfate and polyoxyethylene dodecyl ethers in solution

The effect of polyoxyethylene type nonionic surfactants (C₁₂E _n n = 3, 4, 5, 6, 7 and 8) on the aqueous solution of sodium dodecyl sulfate (SDS) in absence and presence of NaCl was examined using small-angle neutron scattering (SANS), dynamic light scattering (DLS), and viscosity measurements. Upon addition of C₁₂E _n , micellar size of SDS was found to increase significantly, and such micellar elongation was further enhanced in the presence of NaCl. Micellar growth is most significant in presence of shorter moieties of C₁₂E _n (e.g., n = 3, 4) as compared to higher ethereal oxygen content. The results of structural investigations with SANS and DLS to confirm this assumption are reported. The cloud point of C₁₂E _n has increased upon addition of SDS and decrease with NaCl, and a typical behavior is observed when both SDS and NaCl were present.     

Micellar and Mixed-Micellar Effects on Alkaline Hydrolysis of tris(1,10–phenanthroline)iron(II): Kinetic Exploration

The kinetics of alkaline hydrolysis of tris(1,10–phenanthroline)iron(II) has been studied in the presence of nonionic and mixed nonionic–ionic micellar media at 308 K. The effects of mixed-micellar environments of nonionic with ionic surfactants (C₁₂E₂₃/ATABs and C₁₂E₂₃/SDS) on the hydrolytic rate have been studied. The rate decreases monotonically with an increment of [C₁₂E₂₃]_T (total Brij 35 concentration) at constant [^?OH]₀ and has been discussed with the pseudo-phase micellar model. The rate also decreases with [C₁₂E₂₃]_T at a continuous addition of ionic surfactants (ATABs and SDS). The observed rate constant k_obs follows the empirical relation: k_obs = (k₀ + θK [C₁₂E₂₃]_T)/(1 + K [C₁₂E₂₃]_T) (where θ and K are empirical constants). The values of θ remain unaffected, whereas K decreases nonlinearly with [ATABs]_T in a mixed C₁₂E₂₃?ATAB micellar system. But the k_obs in a mixed C₁₂E₂₃–SDS micellar system is much lower than that of the C₁₂E₂₃–ATAB system and do not comply with any micellar kinetic models.     

Calorimetric study of binary systems of tetraethyleneglycol octylether and polyethyleneglycol with water

Calorimetric measurements have been made of the differential enthalpies of solution as a function of composition of both components in the binary systems tetraethyleneglycol octylether (C₈E₄)-water and polyethyleneglycol 400 (PEG)-water, as a function of composition, at three different temperatures. Heat capacity changes for dissolution were calculated from the temperature variation of the solution enthalpies. Excess enthalpies and excess heat capacities of mixing were calculated from the differential enthalpies of solution. All measurements on C₈E₄ were made above the critical micelle concentration (c.m.c.) so the results relate to C₈E₄ in aggregated form. The thermochemical properties of the C₈E₄ and PEG systems with water are similar. The differential solution enthalpy of the organic solute in pure water is fairly exothermic and then increases smoothly with increasing solute content. Likewise the solution enthalpy of water in pure C₈E₄ or PEG is fairly exothermic, but increases steadily to become zero at a water content corresponding to more than five water molecules per ethyleneoxide group. The measurements on the C₈E₄ system at 40°C were made close to the demixing temperature. The results are compared with previously reported results on the 2-butoxyethanol (BE)-water system.     

Effects of Cs and Na ions on the interfacial properties of dodecyl sulfate solutions

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     

Electrokinetic chromatographic characterization of novel catanionic surfactants vesicle as pseudostationary phase

A novel catanionic surfactants vesicle system composed of octyltriethylammonium bromide/ sodium dodecyl benzene sulfonate (C₈NE₃Br/SDBS) has been developed as pseudostationary phase (PSP) in EKC. The C₈NE₃Br/SDBS system possesses a large vesicle phase region and none of agglomeration phenomena appeared while mixing cationic and anionic surfactants at any molar ratio. Electrophoretic and chromatographic parameters including elution window, hydrophobic selectivity, polar group selectivity, and shape selectivity were characterized using the vesicle at molar ratio of C₈NE₃Br to SDBS of 3:7 as PSP. Compared with SDS micelles, the vesicle PSP possessed a wider elution window and a better selectivity. The retention behavior and selectivity differences between the novel vesicle and SDS micelles were evaluated through linear solvation energy relationship (LSER) analysis. Though the cohesiveness and the hydrogen bond acidity have greatest influences on the solutes retention and selectivity in both the vesicle and SDS micelle, the vesicle PSP demonstrated a higher hydrophobicity and a lower hydrogen bonding donating capability owing to compact bilayer structure of vesicle. Additionally, the vesicle system had a stronger hydrogen bond accepting capability than SDS micelle. Consequently, according to LSER analysis, the bigger coefficients for v, b, and a revealed the vesicle PSP had a better separation selectivity than conventional SDS micelle.     

Synthesis and properties of nonylphenol-substituted dodecyl sulfonate

Nonylphenol-substituted dodecyl sulfonate (C₁₂-NPAS) was synthesized via sulfonation-alkylation-neutralization using 1-dodecene, SO₃, and nonylphenol as raw materials. The properties such as surface tension, interfacial tension (IFT), wettability, foam properties, and salinity tolerance of C₁₂-NPAS were systematically investigated. The results show that the critical micelle concentration (CMC) of C₁₂-NPAS was 0.22?mmol?·?L^?1 and the surface tension at the CMC (γ_CMC) of C₁₂-NPAS was 29.4 mN/m. When compared with the traditional surfactants sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and linear alkylbenzene sulfonate (LAS), the surface properties of C₁₂-NPAS were found to be superior. The IFT between Daqing crude oil and a weak-base alkaline/surfactant/polymer (ASP) oil flooding system containing 0.1?wt% of C₁₂-NPAS can reach an ultralow level of 2.79?×?10^?3 mN/m, which was lower than that found for the traditional surfactant heavy alkylbenzene sulfonate (HABS). The salinity and hardness tolerance of C₁₂-NPAS were much stronger than those found for conventional surfactants, petroleum sulfonate, and LAS. C₁₂-NPAS also shows improved wetting performance, foamability, and foam stability.     

Interaction of Novel Anionic Gemini Surfactants with Dodecyl Sodium Sulfate in Aqueous NaCl Medium and the Performance of Their Mixtures

The interaction in two mixtures of two novel anionic gemini surfactants, sodium 2,2′-(6,6′-(ethane-1,2-diylbis(azanediyl)bis(4-(hexylamino)-1,3,5-triazine-6,2-diyl)bis(azanediyl)diethanesulfonate (C₆-2-C₆) and sodium 2,2′-(6,6′-(ethane-1,2-diylbis(azanediyl)bis(4-(octylamino)-1,3,5-triazine-6,2-diyl) bis(azanediyl) diethanesulfonate (C₈-2-C₈), and conventional anionic surfactants, sodium dodecyl sulfate (SDS), have been investigated in 0.1 M NaCl aqueous solutions. The mixed systems are C₆-2-C₆/SDS and C₈-2-C₈/SDS, and the mole factions (α_G) of geminis are 0.1, 0.3, 0.5, 0.7, and 0.9, respectively. Mixtures of both C₆-2-C₆/SDS and C₈-2-C₈/SDS exhibit synergism in surface tension reduction efficiency and mixed micelle formation. But, all mixtures except C₆-2-C₆/SDS (α_G = 0.7), C₆-2-C₆/SDS (α_G = 0.9), and C₈-2-C₈/SDS (α_G = 0.1) don't exhibit synergism in surface tension reduction effectiveness. The performances, such as wetting, emulsification, and dispersion were measured and the results showed all mixtures posses application properties.     

Synergistic behavior of sodiumdodecylsulfate and 1,2-diheptanoyl-sn- glycero-3-phosphocholine in an aqueous medium: interfacial and bulk behavior

The synergistic behavior of sodiumdodecylsulfate (SDS) and 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) binary mixtures has been studied with interfacial and pyrene fluorescence(I ₁/ I ₃) intensity measurements. From the interfacial data, the interfacial parameters; the maximum surface excess (Γ_max), or the minimum area per molecule (A _min), and the surface pressure at the critical micellar concentration (π_cmc) have been evaluated. The cmc value has been used for evaluating the free energies of micellization (ΔG ^o _m). The mixed micelle formation was evaluated with the help of the Clint equation. The SDS plus DHPC mixed micelles showed negative departure from ideality indicating synergistic interactions between the unlike components. The quantitative analysis of mixed micelle, mixed monolayer and the composition of the mixed micelle was carried out with the help of regular solution approximation. The interaction parameters, β and β^σ, in the mixed micelle as well as in the mixed monolayer, respectively showed negative values indicating synergistic behavior of SDS and DHPC molecules.     

The effect of surfactants on adsorbed layers of a cationic polyelectrolyte

A comparative study of the influence of anionic (sodium dodecyl sulfate, SDS), cationic (tetradecyltrimethylammonium bromide, TTAB) and non-ionic (penta-ethyleneglycol mono n-dodecyl ether, C₁₂E₅) surfactants on the structure and composition of adsorbed layers of cationic hydrophobically modified hydroxyethylcellulose (Quatrisoft LM 200) on hydrophilic surfaces (mica and silica) was carried out using surface force apparatus andin situ null ellipsometry. It is shown that a complex interplay of electrostatic, hydrophobic, and steric effect govern polymer/surfactant/surface interactions and that the effect of surfactant addition strongly depends on its nature and concentration.Both anionic and non-ionic surfactants exhibit aggregation on the polymer hydrophobes. SDS has the most profound influence on Quatrisoft interfacial behavior due to the changes in electrostatics accompanying formation of the polymer/surfactant complex. In the case of C₁₂E₅, large surfactant clusters bound to the polymer affect the macromolecules' conformation in the adsorbed layer via steric effects. In contrast to SDS and C₁₂E₅, no evidence of interaction between the polycation and a like-charged surfactant, TTAB, was obtained. At the same time, TTAB adsorbs on the surface in competition with the polyelectrolyte. This results in partial displacement of the latter and its looser attachment to the surface.     

Studies on the Physicochemical Properties of 3-Alkoxyl-2-hydroxypropyl Trimethylammonium Chloride–Sodium Dodecyl Sulfonate Binary-Surfactant Aqueous Systems

Surface tension, micelle formation, surface adsorption, and solubilization of dimethylaminoazobenzene (DMAB) are studied in aqueous solutions of 3-alkoxyl-2-hydroxypropyl trimethylammonium chloride (alkoxyl = C_nH_2n+1O, n = 8, 12, 14, 16), of sodium dodecyl sulfonate, and of mixtures of these cationic surfactants and the anionic surfactant at 40°C. Synergistic effects on micelle formation, surface tension reduction, and solubilization enhancement of DMAB are observed in the cationic–anionic mixed surfactant systems. The experimental results are discussed in the light of the interactions between the two kinds of surfactant ions.     

Decreased surfactant activity coefficients in polymer-surfactant mixtures

The SDS unimer concentration in a series of mixed anionic/non-ionic surfactant solutions comprising sodium dodecylsulphate (SDS) and sugar-based dodecyl bis-N-methyl gluconamides (C₁₂BNMG) have been studied using an anionic surfactant selective electrode, both in the presence and absence of the polyampholyte gelatin. The activity of the SDS has been calculated at the critical micelle concentration (CMC) in the gelatin-free studies and at CMC(1) in the gelatin studies. From the known solution composition, the activity coefficients can be calculated; these show deviations from unity around a solution mole fraction (_SDS) of 0.95 SDS in both cases. The deviation is significantly greater in the presence of gelatin, to an extent that the SDS activity versus _SDS curve exhibits a maximum and a minimum in the region _SDS=0.8–1.0, consistent with the possibility of coexisting micelle types, in agreement with our earlier NMR study (Griffiths et al. (1998) J Chem Soc Chem Comm 1:53).     

Methanofullerene Molecular Scaffolding: Towards C60-substituted poly(triacetylenes) and expanded radialenes,preparation of a C60–C70 hybrid derivative,and a novel macrocyclization reaction

The synthesis of (E)-hex-3-ene-l, 5-diynes and 3-methylidenepenta-1, 4-diynes with pendant methano[60]-fullerene moieties as precursors to C₆₀-substituted poly(triacetylenes) (PTAs, Fig. 1) and expanded radialenes (Fig. 2) is described. The Bingel reaction of diethyl (E)-2, 3-dialkynylbut-2-ene-1, 4-diyl bis(2-bromopropane-dioates) 5 and 6 with two C₆₀ molecules (Scheme 2) afforded the monomeric, silyl-protected PTA precursors 9 and 10 which, however, could not be effectively desilylated (Scheme 4). Also formed during the synthesis of 9 and 10 , as well as during the reaction of C₆₀ with thedesilylated analogue 16 (Scheme 5 ), were the macrocyclic products 11, 12 , and 17 , respectively, resulting from double Bingel addition to one C-sphere. Rigorous analysis revealed that this novel macrocyclization reaction proceeds with complete regio- and diastereoselectivity. The second approach to a suitable PTA monomer attempted N, N′-dicyclohexylcarbodiimide(DCC)-mediated esterification of (E)-2, 3-diethynylbut-2-ene-l, 4-diol ( 18 , Scheme 6) with mono-esterified methanofullerene-dicarboxylic acid 23 ; however, this synthesis yielded only the corresponding decarboxylated methanofullerene-carboxylic ester 27 (Scheme 7). To prevent decarboxylation, a spacer was inserted between the reacting carboxylic-acid moiety and the methane C-atom in carboxymethyl ethyl 1, 2-methano[60]fullerene-61, 61-dicarboxylate ( 28 , Scheme 8), and DCC-mediated esterification with diol 18 afforded PTA monomer 32 in good yield. The formation of a suitable monomeric precursor 38 to C₆₀-substituted expanded radialenes was achieved in 5 steps starting from dihydroxyacetone (Schemes 9 and 10), with the final step consisting of the DCC-mediated esterification of 28 with 2-[1-ethynyl(prop-2-ynylidene)]propane-1, 3-diol ( 33 ). The first mixed C₆₀-C₇₀ fullerene derivative 49 , consisting of two methano[60]fullerenes attached to a methano[70]fullerene, was also prepared and fully characterized (Scheme 13). The C_s-symmetrical hybrid compound was obtained by DCC-mediated esterification of bis[2-(2-hydroxy-ethoxy)ethyl] 1, 2-methano[70]fullerene-71, 71-dicarboxylate ( 46 ) with an excess of the C₆₀-carboxylic acid 28 . The presence of two different fullerenes in the same molecule was reflected by its UV/VIS spectrum, which displayed the characteristic absorption bands of both the C₇₀ and C₆₀ mono-adducts, but at the same time indicated no electronic interaction between the different fullerene moieties. Cyclic voltammetry showed two reversible reduction steps for 49 , and comparison with the corresponding C₇₀ and C₆₀ mono-adducts 46 and 30 indicated that the three fullerenes in the composite fullerene compound behave as independent redox centers.     

Spectroscopic analysis of naphtholazobenzimidazole in organised solution

Micelle–water partition coefficient (K_x ) of naphtholazobenzimidazole dye (NAB) in aqueous solutions of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) has been determined spectrophotometerically. Changes in absorption patterns of dye caused by surfactants and solvents were quantified in terms of dye–surfactant ratio (n _D/n _S) and solvent water partition coefficients (P), respectively. Multiple residence sites have been suggested for dye molecules within micelles, based on shifts in azo-hydrazone tautomeric equilibrium. Micelle–water partition coefficients were used to evaluate the influence of dye on critical micelle concentration of CTAB and SDS. At same micelle concentration, M, the relative solubility of NAB was greater in cationic surfactant CTAB than in anionic surfactant SDS.     

Properties of aqueous solution of sodium glycocholate and a nonionic surfactant,and their mixtures

The micellar properties of aqueous binary mixed solutions of sodium glycocholate, NaGC, and octa-oxyethylene glycol mono-n-decyl ether, C₁₀E₈, have been studied on the basis of surface tensions, the mean aggregation number and the polarity of the interior of the micelles. The mean aggregation number, measured by steady state quenching method, decreased with the increase of the mole fraction of NaGC in the mixed system. The polarity of the interior, estimated by the ratio of first and third vibronic peak in a monomeric pyrene fluorescence emission spectrum, suggested that the hydrophobicity of intramicelles increased with the increase of the mole fraction of NaGC in the mixed system. These are considered to be caused by the differences in the chemical structure and the hydrophobic nature between NaGC and C₁₀E₈. The mean aggregation number and the polarity of the interior for each micelle near the CMC in lower total concentration of surfactants showed the tendency approaching those of pure micelle of the nonionic surfactant. This suggests that the ratio of NaGC in the initial micelles in the range of lower total concentration near the CMC is lower than that of the corresponding prepared mole fraction in the mixed system. This lower value was confirmed also from theoretical calculation of the ratio of NaGC at the CMC in the mixed micelle by regular solution treatment of Rubingh in the solution.