Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface

Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br⁻ counterions compared to smaller Na⁺ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H⁺ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H⁺ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.     

Foams stabilized by mixed cationic gemini/anionic conventional surfactants

The mixed adsorption of a cationic gemini surfactant, ethanediyl-1,2-bis(dodecyldimethylammonium bromide) (abbreviated as 12-2-12), and an anionic conventional surfactant, sodium dodecyl sulfate (SDS), was examined using surface tension measurements. The viscoelastic properties of the mixed films were investigated by dilational interfacial rheology technique. The results showed that the addition of SDS promoted the close packing of adsorbed molecules at the interface, which increased the dilational elasticity of the mixed films. The stability of the foams was determined by the half-life of foam height collapse. The foams generated by 12-2-12/SDS mixtures were more stable than that formed by pure 12-2-12. In the presence of sodium bromide, the foam stability was further enhanced and the surfactant concentration required to attain the maximum effect in stabilizing foams was greatly reduced. The high foam stability could well relate to the high elasticity of the film.     

The Influence on Interfacial Tension of the Combination of Anionic and Cationic Surfactants: Alkyl Sulfonate/Alkyltrimethylammonium Bromide

Mioellization of aqueous mixture of sodium octyl sulfonate ( C₈As )/ cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfonate (C₁₂As)( CTAB in the presence of sodium bromide has been studied by surface tension measurement. Nonideal solution theory has been used to calculate the molecular interaction parameters (β^M and β^s). The oil-aqueous interfacial tensions of C₁₂As/ CTAB, C₈As/CTAB, C₁₂As/dodecyl trimethylammonium bromide (DTAB) systems were also measured. We studied the influence of the surfactant concentration, surfactant molar fraction ratio, hydrocarbon chain length, added NaCl and alcohol concentration on the interfacial tension.     

Hydrophobically Associating Alginate Derivatives: Surface Tension Properties of Their Mixed Aqueous Solutions with Oppositely Charged Surfactants

The comparative study of the interfacial properties of an anionic polysaccharide, sodium alginate (Alg), and its hydrophobically modified derivative (Alg-C(12)), covalently substituted by dodecyl chains (12% mol/mol saccharide unit), was carried out in the absence or in the presence of an oppositely charged surfactant, dodecyltrimethylammonium bromide (DTAB). The drastically different behaviors which were observed are interpreted in terms of the arrangement and mobility of the hydrophobic long alkyl chains, depending on the nature of their fixation, covalent or ionic, on the polysaccharide backbone. Copyright 2000 Academic Press.     

油/水界面表面活性剂的复配协同机制

采用耗散颗粒动力学(DPD)方法模拟了椰油酸二乙醇酰胺(6501)分别与十二烷基-α-烯烃磺酸钠(DAOS)、椰油酰胺丙基二甲基甜菜碱(CAB)和十二烷基苯磺酸钠(SDBS)复配体系中表面活性剂在油/水界面的排布行为, 探讨了盐度及分子结构对单一和复配表面活性剂界面活性的影响, 从界面效率、界面密度和分子排布等角度讨论了油水界面表面活性剂混合体系的复配协同增效机制.     

A Study of Dynamic Interfacial Properties as Related to Foaming Properties of Sodium 2,5-dialkyl Benzene Sulfonates

In this article, foaming properties and dynamic interfacial properties of a series of sodium 2,5-dialkyl benzene sulfonates in aqueous solutions were carried out to elucidate the relationship between foaming properties and dynamic interfacial properties. The properties of foams generated from bubbling air through different surfactant solutions were measured using a modified Bikerman device. The dynamic surface tension and surface dilational elasticity were obtained from an image analysis technique based on the oscillating bubble method. The surfactants molecular adsorption at the air/water interface was introduced with Rosen empirical equation and the rate of adsorption was determined from measurements of the dynamic surface tension. The surfactant with the longest alkyl chain shows the lowest dynamic surface activity, which lead to the lowest foam volume. The short ortho straight alkyl chain has little effect on the arrangement of molecules at the interface and the foam stability changes a little with the changing of the ortho alkyl chain length. The foam stability is correlated with both the higher surface dilational elasticity and the larger surface monolayer strength.     

Surface properties of mixed monolayers of sulfobetaines and ionic surfactants

To study the influence of the head group in the properties of the mixed monolayers adsorbed at the air-water interface, the surface tension and surface potential of binary mixtures of surfactant have been determined as a function of the surfactant composition. Experiments were carried out with anionic-zwitterionic sodium dodecyl sulfate and dodecyl dimethyl ammoniopropane sulfonate (SDS/DDPS), and cationic-zwitterionic dodecyl trimethylammonium bromide and dodecyl dimethyl ammoniopropane sulfonate (DTAB/DDPS), and dodecyl trimethylammonium bromide and tetradecyl dimethyl ammoniopropane sulfonate (DTAB/TDPS). It was shown that mixed monolayers of cationic-zwitterionic surfactant exhibit small negative deviations of ideal behavior, whereas for SDS/DDPS monolayers show strong negative deviation from the ideality. Deviations of ideal behavior are interpreted by regular solution theory. The surface potential values agree very well with the concentration of the ionic component at the interface. The dynamic surface tension values show that the adsorption kinetics on the interface is a diffusion-controlled process. In monolayers with significant deviation of the ideal behavior, anionic-zwitterionic, there is some evidence of intermolecular attractions after diffusion of both surfactants at the interface.     

Effect of surfactant structure on catalysis of microemulsion for photoisomerization of trans-stilbene

In this study,the photoisomerization of trans-sfilbene was carried out in water in oil (W/O) microemulsions by using sodium dodecyl sulfate (SDS),dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) as surfactant,respectively.The catalytic effect of microemulsion on this reaction is closely related to the structure of surfactant.When there is no photosensitizer 9,10-dicyanoanthracene (DCA),the surfactant with shorter hydrophobic chain is preferred,while in the presence of DCA,the surfactant with anionic polar group is preferred.     

Dilational viscoelasticity of anionic polyelectrolyte/surfactant adsorption films at the water–octane interface

In this article, the interfacial tension and interfacial dilational viscoelasticity of polystyrene sulfonate/surfactant adsorption films at the water–octane interface have been studied by spinning drop method and oscillating barriers method respectively. The experimental results show that different interfacial behaviors can be observed in different type of polyelectrolyte/surfactant systems. Polystyrene sulfonate sodium (PSS)/cationic surfactant hexadecanetrimethyl–ammonium bromide systems show the classical behavior of oppositely charged polyelectrolyte/surfactant systems and can be explained well by electrostatic interaction. In the case of PSS/anionic surfactant sodium dodecyl sulfate (SDS) systems, the coadsorption of PSS at interface through hydrophobic interaction with alkyl chain of SDS leads to the increase of interfacial tension and the decrease of dilational elasticity. For PSS/nonionic surfactant TX100 systems, PSS may form a sub-layer contiguous to the aqueous phase with partly hydrophobic polyoxyethylene chain of TX100, which has little effect on the TX100 adsorption film and interfacial tension.     

界面张力弛豫法研究芳香侧链酰基牛磺酸钠的界面相互作用

采用界面张力弛豫方法研究了表面活性剂N-(α-苯氧基)十四酸牛磺酸钠(12+B-T),N-(α-乙基苯氧基)十四酸牛磺酸钠(12 +2B-T)和N-(α-己基苯氧基)十四酸牛磺酸钠(12+6B-T)在空气-水表面和癸烷-水界面上的扩张流变性质,考察了芳环支链链长变化对分子界面行为的影响,获得了表面活性剂结构对极限扩张弹...     

1H NMR relaxation of water: a probe for surfactant adsorption on kaolin

In this study, (1)H NMR is used to investigate properties of sodium dodecyl sulfate (SDS), tetradecyl trimethyl ammonium bromide (TTAB), and dodecyl trimethyl ammonium bromide (DTAB) adsorbed on kaolin by NMR T(1) and T(2) measurements of the water proton resonance. The results show that adsorbed surfactants form a barrier between sample water and the paramagnetic species present on the clay surface, thus significantly increasing the proton T(1) values of water. This effect is attributed to the amount of adsorbed surfactants and the arrangement of the surfactant aggregates. The total surface area covered by the cationic (DTAB and TTAB) and anionic (SDS) surfactants could be estimated from the water T(1) data and found to correspond to the fractions of negatively and positively charged surface area, respectively. For selected samples, the amount of paramagnetic species on the clay surface was reduced by treatment with hydrofluoric (HF) acid. For these samples, T(1) and T(2) measurements were taken in the temperature range 278-338 K, revealing detailed information on molecular mobility and nuclear exchange for the sample water that is related to surfactant behavior both on the surface and in the aqueous phase.     

Interaction of Sodium Dodecyl Sulfate with Poly(ethyleneimine) in Bulk Solution and at the Air-Solution Interface

Interaction of sodium dodecyl sulfate (SDS) with the cationic polyelectrolyte poly(ethyleneimine) (PEI) was investigated in this study. Turbidity measurements were performed in order to analyze the interaction and complex formation in bulk solution as a function of polymer concentration and pH. Surface tension measurements were made to investigate the properties of SDS/PEI/water mixtures at air/solution interface. Results revealed that SDS/PEI complexes form in solution depending on the surfactant and polymer concentration. A decrease was observed in surface tension values in the presence of SDS/PEI mixtures compared to the values of pure SDS solutions. Both solution and interfacial properties exhibited pH dependent behavior. A shift was seen in the critical micelle concentration of SDS solutions as a function of PEI concentration and solution pH. Monovalent and divalent salt additions showed some influence on the interfacial properties of SDS solutions in the presence of PEI.     

不同结构三取代烷基苯磺酸钠表、界面的扩张性质

利用悬挂滴方法研究了两种同分异构体的表面活性剂2-丙基-4,5-二己基苯磺酸钠(366)和2,5-二丙基-4-壬基苯磺酸钠(393)在空气/水表面和癸烷/水界面上的扩张流变性质, 考察了不同表面活性剂浓度下366和393溶液表、界面扩张性质的异同. 实验结果表明, 磺酸根间位的长链烷基对表面扩张模量贡献较大, 表面活性剂分子大小对界面扩张模量影响较大.     

卵清蛋白与离子型表面活性剂的相互作用

本文通过荧光光谱法、紫外-可见吸收光谱法和透射电镜并结合电导率测定分别研究了水中卵清蛋白与阴离子表面活性剂十二烷基硫酸钠（SDS）和阳离子表面活性剂十二烷基三甲基溴化铵（DTAB）和十六烷基三甲基溴化铵（CTAB）之间的相互作用。研究结果表明卵清蛋白可以增加SDS和CTAB的临界胶束浓度,但对DTAB的临界胶束浓度没有影响。阴离子表面活性剂可以使卵清蛋白构象完全伸展,而阳离子表面活性剂却不具备此种作用。表面活性剂单体与卵清蛋白的相互作用强于表面活性剂胶束与卵清蛋白的相互作用。     

Effect of surfactant type on surfactant-maltodextrin interactions: isothermal titration calorimetry, surface tensiometry, and ultrasonic velocimetry study

Isothermal titration calorimetry (ITC), surface tensiometry, and ultrasonic velocimetry were used to characterize surfactant-maltodextrin interactions in buffer solutions (pH 7.0, 10 mM NaCl, 20 mM Trizma base, 30.0 degrees C). Experiments were carried out using three surfactants with similar nonpolar tail groups (C12) but different charged headgroups: anionic (sodium dodecyl sulfate, SDS), cationic (dodecyl trimethylammonium bromide, DTAB), and nonionic (polyoxyethylene 23 lauryl ether, Brij35). All three surfactants bound to maltodextrin, with the binding characteristics depending on whether the surfactant headgroup was ionic or nonionic. The amounts of surfactant bound to 0.5% w/v maltodextrin (DE 5) at saturation were < 0.3 mM Brij35, approximately 1-1.6 mM SDS, and approximately 1.5 mM DTAB. ITC measurements indicated that surfactant binding to maltodextrin was exothermic. Surface tension measurements indicated that the DTAB-maltodextrin complex was more surface active than DTAB alone but that SDS- and Brij35- maltodextrin complexes were less surface active than the surfactants alone.     

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.     

Effect of surfactants on the rate of growth of an air bubble by rectified diffusion

The rectified diffusion growth of a single air bubble levitated in an acoustic field (frequency = 22.35 kHz) in water and in aqueous solutions containing surfactants (sodium dodecyl sulfate and sodium dodecylbenzene sulfonate) was investigated. As reported by Crum (J. Acoust. Soc. Am. 1980, 68, 203), the presence of surfactants at the bubble/liquid interface enhanced the growth rate of the bubble by rectified diffusion. It is suggested in this paper that in addition to the effect of surfactants on the surface tension and interfacial resistance to mass transfer, the effect of surface rheological properties may also contribute to the cause of the enhancement observed in the bubble growth rate.     

烷基苯磺酸盐在油水界面行为的介观模拟

采用耗散颗粒动力学(DPD)方法在介观层次上模拟了表面活性剂烷基苯磺酸盐在油/水界面的排布行为, 考察了分子结构、浓度、盐度、油相等因素对表面活性剂界面密度和界面效率的影响, 并探讨了利用表面活性剂复配协同效应提高界面活性的理论机制. 分子模拟给出的分子水平的微观信息为强化采油技术中配方筛选和表面活性剂的有效应用提供指导.     

Effect of surfactants on temperature-dependent self-assembling property of copolyethylenimine/cinnamic acid aqueous mixture

The transmittance of polyethylenimine (PEI)/cinnamic acid (CA) aqueous mixture was close to zero at 20–40°C, and it began to increase around 40°C due to the disassembling of the self-assembly of the PEI/CA conjugate. As the concentration of sodium dodecyl sulfate (SDS) increased, the increasing rate of the transmittance decreased and the onset temperature increased, indicating that the self-assembly of the PEI/CA conjugate became more stable against heat with the aid of SDS. Tween 20 could also suppress the thermally induced disassembling of the self-assembly, possibly because poly(ethylene oxide) chains of the surfactant could be entangled with the PEI chains. Dodecyltrimethyl ammonium bromide (DTAB) did not have an effect on the temperature-dependent self-assembling phenomena as much as SDS and Tween 20 did. The interfacial tension of the PEI/CA/SDS aqueous mixture and that of the PEI/CA/Tween 20 aqueous mixture at 70°C were lower than the respective tensions observed at 25°C. On the contrary, the interfacial tension of the PEI/CA/DTAB aqueous mixture at 70°C was higher than that observed at 25°C, possibly because the PEI/CA conjugate could lose its surface activity at the higher temperature due to the adsorption of DTAB on CA molecules.     

Surfactant-mixing effects on the interfacial tension and the microemulsion formation in water/supercritical CO2 system

The effects of surfactant mixing on interfacial tension and on microemulsion formation were examined for systems of air/water and water/supercritical CO2 (scCO2) interfaces and for water/scCO2 microemulsions. A fluorinated surfactant, sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), was mixed with the three hydrocarbon surfactants, Pluronic L31, Tergitol TMN-6, and decyltrimethylammonium chloride (DeTAC), at equimolar ratio. For all the cases, the interfacial tension was significantly lowered by the mixing. The positive synergistic effect suggests that the mixed surfactants tend to pack more closely on the interface than the pure constituents. It was found, however, that the microemulsion formation in scCO2 was never facilitated by the mixing, except for the case of TMN-6. This is probably due to the segregation of the surfactants into hydrocarbon-rich and fluorocarbon-rich phases on the microemulsion surface.