Krafft Temperature,Critical Micelle Concentration,and Rheology of “Pseudo-Gemini” Surfactant Comprising Fatty Acid Soap and Bola-Type Quaternary Ammonium Salt

Bola-type quaternary ammonium salt can bridge with two fatty acid soaps through electrostatic attraction to form a pseudogemini surfactant, which enhances the solution viscosity. In this work, the effects of the building blocks (spacer and hydrophobic chain) of a pseudogemini surfactant on the Krafft temperature, critical micelle concentration, and rheological properties were investigated. The results revealed that the addition of bola-type salt obviously decreased the Krafft temperature of sodium stearate (C₁₈ONa), and a bola-type salt bearing a large benzene ring (Bola2be) was more effective than the one bearing an ethyl group (Bola2et) or a hydroxyethyl group (Bola2hy). When bola-type salt is mixed with fatty acid soap at a fixed molar ratio of 1:2, a pseudogemini surfactant forms in situ, and the viscosity of the solution is significantly enhanced by the formation of a worm-like micelle (WLM) network. The stronger the hydrophobicity of the bola-type salt or the tail of the fatty acid soap, the lower the critical overlapping and micelle concentrations, and the stronger is the ability to enhance viscosity. However, pseudogemini surfactants that use sodium stearate as a monomer show similar self-assembly abilities to those using sodium oleate as a monomer. In addition, the WLM formed by pseudogemini surfactants composed of Bola2be and sodium stearate or sodium oleate were liable to branch at high concentrations.     

Effect of tartrazine dye on micellisation of cationic surfactants: conductometric,spectrophotometric, and tensiometric studies

The interactions between anionic dye (tartrazine) and cationic surfactants (dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide) have been studied by conductometric, spectrophotometric, and tensiometric techniques. The conductance and surface tension of dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide in pure water as well as in aqueous tartrazine when plotted with surfactant concentration gave values of the critical micelle concentration at different temperatures. As well as increasing the length of the carbon chain of surfactants, the presence of tartrazine reduces the critical micelle concentration. From specific conductivity data, the counterion dissociation constant, standard free energy, enthalpy, entropy of micellisation, surface excess concentration, surface tension at critical micelle concentration, minimum area per molecule, surface pressure at critical micelle concentration, and Gibbs energy of adsorption were evaluated. Spectroscopic studies reveal that the binding of dye to micelles brings a bathochromic shift in dye absorption spectra that indicates dye–surfactant interaction.     

The study of Sunset Yellow anionic dye interaction with gemini and conventional cationic surfactants in aqueous solution

In the present study, the interaction of an anionic azo dye, Sunset Yellow, with two cationic gemini surfactants with different spacer lengths (s = 3, 6 methylene groups) and their monomeric counterpart, dodecyl trimethyl ammonium bromide (DTAB), was investigated by surface tension, UV–Vis spectroscopy, and zeta potential measurements. The critical micelle concentration (CMC) was determined from plots of the surface tension (γ) as a function of the logarithm of total surfactant concentration. Moreover, the values of binding constants (K_b) of dye-surfactant complexes were calculated by UV–Vis spectroscopy. The UV–Vis spectra showed that the dye–surfactant interaction occurred in the solution at concentrations far below the CMC of each surfactant. The gemini surfactant with a shorter spacer showed stronger interaction with dye in comparison to DTAB and the gemini with longer spacer. The effect of surfactant chemical structure on solubilization of dye-surfactant aggregates at surfactant concentration above CMC was investigated by zeta potential.     

Mono‐, Di‐ and Tetra‐Cationic Surfactants as Carbon Steel Corrosion Inhibitors

Corrosion inhibition of three new synthesized cationic surfactants, N‐(2‐(((Z)‐4‐(pyridin‐4‐yl)but‐3‐en‐1‐yl)amino)ethyl)‐N‐(2‐((E)‐(pyridin‐4‐ylmethylene)amino)ethyl)dodecan‐1‐aminium bromide I(4N), N¹,N²‐didodecyl‐N¹‐((Z)‐4‐(pyridin‐4‐yl)but‐3‐en‐1‐yl)‐N²‐(2‐((E)‐(pyridin‐4‐ylmethylene)amino)ethyl)ethane‐1,2‐diaminium bromide II(4N) and 1‐dodecyl‐4‐((E)‐((2‐(dodecyl(2‐(dodecyl((Z)‐4‐(1‐dodecylpyridin‐1‐ium‐4‐yl)but‐3‐en‐1‐yl)ammonio)ethyl)ammonio)ethyl)imino)methyl)pyridin‐1‐ium bromide IV(4N) on carbon steel was investigated by weight loss, electrochemical impedance spectroscopy and polarization measurements. Results show that the synthesized cationic surfactants inhibit corrosion of carbon steel in 1 M HCl. The inhibitive action occurs by virtue of adsorption on the metal surface following a Langmuir adsorption isotherm model. Polarization curves reveal that the investigated cationic surfactants can be classified as mixed inhibitor types. The variations in the corrosion inhibition efficiency between three cationic surfactants are correlated with their chemical structures, with more hydrophobic surfactants yielding higher inhibition efficiency.     

Solubilisation study of water‐insoluble dye in cationic single/dimeric surfactant micelles: effect of headgroup,non‐polar tail,and spacer chain in aqueous and salt solution

The solubilisation of hydrophobic azo dye Orange OT in aqueous/salt solution in several cationic surfactant micelles was studied using UV‐vis spectroscopy. An attempt was made to correlate dye solubilising strength with adsorption/micellar characteristics. In our experiments we determined the change in solubilisation of hydrophobic dye when added to an aqueous solution of oppositely charged quaternary‐salt‐based cationic surfactants (conventional and gemini) and remarked on the probable location of the solubilised dye in the surfactant micelle. Results highlight the onset of dye solubilisation around the critical micelle concentration of each surfactant, which is influenced by the non‐polar tail, spacer, and polar headgroup, while no dye could be solubilised at concentrations below the critical micelle concentration. Orange OT solubilised almost linearly with increase in surfactant concentration at and above the critical micelle concentration. The change in colour intensity of the dye (darker below the critical micelle concentration, lighter at and above the critical micelle concentration) could be attributed to dye–surfactant interactions. Further dye solubilisation was observed in the presence of salt.     

Some Surface Properties of Polysorbates and Cetyl Trimethyl Ammonium Bromine Mixed Systems

Mixed surfactant solutions consisting of cationic/nonionic surfactants were prepared in different compositions of the components in aqueous solution in order to determine the surface properties. The critical micelle concentration (CMC) of aqueous solutions of the individual surfactants cetyl trimethyl ammonium bromide (CTAB) and polysorbate nonionics, and their mixtures are determined at different proportions. The results show that there is synergistic behavior in mixtures at higher mole fraction of nonionic surfactant. The effect of the alkyl chain on the CMC is also determined.     

Experimental Study of CMC Evaluation in Single and Mixed Surfactant Systems, Using the UV–Vis Spectroscopic Method

In this study, the critical micellar concentration (CMC) of anionic, cationic and nonionic surfactants was determined using the UV–Vis spectroscopic method. Sodium lauryl sulfate (SDS) as anionic, hexadecyl-trimethyl-ammonium bromide as cationic, tert-octylphenol ethoxylates TOPEON (with N = 9.5, 7.5 and 35) and lauryl alcohol ethoxylate (23EO) as nonionic surfactants have been used. Concentration of surfactants varies both from below and above the CMC value in the pyrene solution. In addition, the amount of the CMC was determined using the values from the data obtained from the graph of absorbance versus concentration of surfactants. A comparative study was conducted between the results of the present study and the literature which shows a good agreement, in particular for TOPEO9.5 and LAEO23. Furthermore, the CMC value of SDS (as an ionic surfactant) in the presence of nonionic surfactants was also examined. The result reveals that with addition of small amount of nonionic surfactant to the anionic SDS surfactant, a decline in the CMC value of the anionic–nonionic system relative to the CMC of pure anionic surfactant was observed. In addition and for the first time, the effect of UV irradiation on the size of the micelle formations was studied. It was found that UV irradiation causes the formation of smaller micelles which is of prime concern in membrane technology.     

Inhibition of horseradish peroxidase activity through conformational change in surfactant solution

Surfactants have a considerable potential for inhibiting horseradish peroxidase (HRP) activity; yet, more research is needed to understand the inhibition mechanism to allow for choosing the suitable surfactant candidate as inhibitor. In this study, three traditional surfactants, sodium dodecyl sulfate (SDS), N-dodecyltrimethyl ammonium bromide (DTAB) and N-dodecyldimethyl (3-sulfopropyl) ammonium hydroxide (SB3-12), that share the same (C₁₂) hydrophobic tail but possess different charged head groups, were taken as model surfactant inhibitors, and the enzymatic activity of HRP was assessed in these surfactant solutions. The activity of HRP was inhibited by both anionic SDS and cationic DTAB at dilute concentration even below their critical micelle concentration (cmc), and the electrostatic interaction of the ionic surfactants with some amino residues of HRP was mainly responsible for the inhibition of activity. HRP in a dilute solution of SB3-12, with the latter's concentration being below its cmc, retained a high level of enzymatic activity; but, at concentrations above the cmc of SB3-12, HRP was inhibited owing to the synergetic interaction of the SB3-12 micelle with HRP. Results from circular dichroism (CD) and intrinsic fluorescence spectroscopic analyses of HRP showed the unfolding of the tertiary structure around HRP's heme active site played a critical role in the inhibition, whereas the changes of HRP in the secondary structure and the tertiary structure near its tryptophan residue (Trp117) induced by these surfactants were minor for the inhibition. Based on the experimental results, a relationship between conformation and activity for HRP was suggested.     

Mixed Micellar and Interfacial Interactions of a Triblock Polymer (EO37PO56EO37) with a Series of Monomeric and Dimeric Surfactants

The mixed micellar and interfacial properties of mixtures of triblock polymer (TBP) with a series of monomeric (dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetyltrimethylammonium bromide, and dimeric (dimethylene bis[alkyldimethylammonium bromide], m-2-m, where m = 10, 12, and 14) cationic surfactants were investigated using surface tension and viscosity measurements in aqueous solutions at different temperatures. Various physicochemical properties such as critical micelle concentration, mixed micellar mole fraction, interaction parameter, interfacial, and thermodynamic parameters were evaluated. All the binary mixtures exhibit synergistic interactions which increase with temperature and pass through a minimum with the increase in hydrophobic chain length of the cationic surfactants. The contribution of TBP in mixed micelle formation also increases with the hydrophobic chain length of the surfactants. The interfacial and thermodynamic parameters reveal that the adsorption of the surfactant mixtures at the air–solution interface is more favorable than that of micelle formation and the unfavorable enthalpy changes are overwhelmed by favorable entropy changes. Further, the mixtures of TBP with smaller chain length surfactants show a sharp rise in relative viscosity at higher mole fractions of these surfactants.     

Natural dye–surfactant interactions: thermodynamic and surface parameters

The interaction of two Indian natural dyes, namely madder (Rubia cordifolia) and mallow (Punica granatum), with cationic surfactant cetyl trimethyl ammonium bromide and anionic surfactant sodium lauryl sulphate, has been studied. Spectrophotometric data showed a strong interaction between the natural dyes and the surfactants. The critical micelle concentration of the surfactants, determined by measurement of specific conductance and surface tension, was found to decrease on the addition of natural dyes in an aqueous solution of surfactants. The thermodynamic and surface parameters for the interaction have been evaluated.     

二元表面活性剂体系微乳液的相行为及热力学研究

用表面张力法研究了苯乙烯基酚聚氧乙烯聚氧丙烯醚嵌段型非离子表面活性剂(PEP)分别与十二烷基硫酸钠(SDS)、十二烷基三甲基溴化铵(CTAB)复配体系分子间的相互作用,并根据测定的临界胶束浓度(CMC)及正规溶液理论计算了复配体系分子间相互作用参数及分子交换能,考察了表面活性剂、助表面活性剂、温度等因素对复配表面活性剂体系微乳液形成过程的相行为及热力学性质的影响。结果表明,二元组分(PEP+SDS)及(PEP+CTAB)复配体系在胶束中和表面吸附层中的都存在较强的增效作用,体系的能量降低,且前者的增效作用大于后者。(PEP+SDS)/正己醇/正庚烷/水微乳液的W/O微乳区域面积最大,温度对该微乳液的相行为影响很小。在此微乳液形成的过程中,助表面活性剂醇从连续油相进入微乳液界面层的标准自由能变化ΔGs0;标准焓变-ΔHs=0,为无热效应过程,ΔGs是由醇分子的混乱度熵变ΔSs决定的。     

Amino Acid-Functionalized Calix[4]Resorcinarene Solubilization by Mono- and Dicationic Surfactants

Poorly water-soluble calix[4]resorcinarenes modified with amino acid (Ala, Val) at the upper rim formed a water-soluble mixed system with micelles of monocationic surfactants cetyltrimethylammonium bromide, cetyldimethyl(2-hydroxyethyl)ammonium bromide, and dicationic (gemini) surfactants, alkanediyl-α,ω-bis(dimethyltetradecylammonium bromides (14-s-14, where s = 2, 4, or 6). UV–Vis and DLS methods demonstrated that the micellar systems of surfactant/functionalized calix[4]resorcinarene underwent structural changes within a relatively narrow concentration range followed by changes in solubilization capacity and polydispersity. Gemini surfactants and monocationic/gemini mixed surfactant systems were provided selectivity in their interaction with calix[4]resorcinarene depending on the bulkiness of the substituent at the upper rim of calix[4]resorcinarene, gemini surfactant spacer length, and mixed micelles. These systems represent a direction to create biocompatible water-soluble functionalized calix[4]resorcinarene composition and may open perspectives in designing organized systems with controllable properties.     

Polymer–surfactant interactions in graft copolymer solutions

Graft copolymers composed of water-soluble cellulosic backbones and > 0.4% (by weight) alkyl grafts are insoluble in water but soluble in surfactant solutions. Studies of the bulk viscosity and stability of polymer-surfactant solutions at 49°C indicate that the mechanism for solubilization of the polymer is the incorporation of the alkyl side chains into surfactant micelles. The tendency for side chains to combine with micelles appears to depend at least in part on the geometry of the surfactant tail group such that surfactants containing straight-chain tail groups solubilize alkyl side chains more readily than olefinic surfactants. The presence of small solutes near the surface of the micelle also inhibits incorporation of side chains from the polymer. Unsolubilized side chains remain in the aqueous phase of the solution, where they form thermally unstable intermolecular aggregates.     

Properties of aqueous solution of a fluorocarbon surfactant and a nonionic surfactant,and their mixtures

The surface tensions of aqueous solutions of lithium perfluorooctane sulfonate (LiFOS) and hexaethyleneglycoln-dodecylether (6ED), and of their mixtures, were measured. The effect of each surfactant additives on the adsorption and the micelle formation was discussed on the basis of the surface tension values using the Langmuir adsorption equation for the mixture of both surfactants and the modified Szyszkowski equation. From these results, in the range of low concentrations of 6ED or LiFOS, some of the 6ED molecules which had already adsorbed on the solution surface were found to be replaced by LiFOS molecules in an addition of LiFOS surfactant and vice-versa. In the ranges of higher concentration above critical micelle concentration (CMC) of each surfactant, it was concluded that the mixed micelle could be formed in the mixed system of both surfactants as well as in the mixed system of two kinds of ordinary hydrocarbon surfactants.     

Synthesis,Characterization and Effect of a Solvent Mixture on the CMC of a Thio-Based Novel Cationic Surfactant Using a UV–Visible Spectroscopic Technique

A novel thio-based cationic surfactant has been synthesized by a new method. It was characterized by different techniques such as NMR, FTIR and its critical micelle concentration was determined by a UV–Visible spectroscopic technique. It is soluble in polar solvents like ethanol and partially soluble in water due to its thio-based functionality. The detailed study of the compound 4-chloro-N-((dodecanoyl(ethyl)ammonio)carbonothioyl)-N-ethylbenzenaminium bromide (4CDTB) was done using a UV–Visible spectrophotometric technique. The effect of solvent mixtures of different ratios was investigated. On the basis of solvent–solvent interaction the compound showed different results. The critical micelle concentration varied with solvent mixture ratios. The CMC of 4CDTB decreased as the ratio of water increased in the mixture of the ethanol–water system. The decrease in critical micelle concentration with the solvent mixture ratio has been discussed on the basis of solvent properties, structures, and their hydrophilic and hydrophobic interactions.     

A Zwitterionic Surfactant Bearing Unsaturated Tail for Enhanced Oil Recovery in High‐Temperature High‐Salinity Reservoirs

High‐temperature/high‐salinity (HTHS) reservoirs contain a significant fraction of the world's remaining oil in place and are potential candidates for enhanced oil recovery (EOR). Selection of suitable surfactants for such reservoirs is a challenging task. In this work, two synthesized zwitterionic surfactants bearing a saturated and an unsaturated tail, namely 3‐(N‐stearamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate and 3‐(N‐oleamidopropyl‐N,N‐dimethyl ammonium) propanesulfonate, respectively, were evaluated. The surfactant with the unsaturated tail showed excellent solubility in synthetic seawater (57,643 ppm) and in formation brine (213,734 ppm). However, the unsaturated surfactant with a saturated tail showed poor solubility, and therefore it was not evaluated further. The thermal stability of the synthesized unsaturated surfactant solution in seawater was evaluated by heating the solution at 90 °C in a sealed aging tube for 2 weeks. The thermal stability of the unsaturated surfactant was confirmed by FTIR and NMR analysis of the aged samples at such harsh conditions. The critical micelle concentration (CMC) of the synthesized unsaturated surfactant in seawater was 1.02 × 10^?4 mol L^?1, while the surface tension at CMC was 30 mN m^?1. The synthesized unsaturated surfactant was able to reduce the oil–water interfacial tension to ~10^?1 mN m^?1 at different conditions. A commercial copolymer of acrylamide and 2‐acrylamido‐2‐methylpropane sulfonic acid (AM‐AMPS) was tested for EOR applications in HTHS conditions. The addition of the synthesized unsaturated surfactant to the AM‐AMPS copolymer increased the viscosity of the system. The increase in oil recovery by injecting the unsaturated surfactant solution and the surfactant–polymer mixture in solution was 8 and 21%, respectively. The excellent properties of the synthesized unsaturated surfactant show that surfactants with an unsaturated tail can be an excellent choice for HTHS reservoirs.     

去氢枞酸基新型甜菜碱类两性表面活性剂的合成

从歧化松香中分离提纯去氢枞酸,然后以去氢枞酸为原料,经去氢枞酸缩水甘油酯及叔胺中间体,合成了N-(3-去氢枞酰氧基-2-羟基)丙基-N,N-二甲基羧甲基甜菜碱和N-(3-去氢枞酰氧基-2-羟基)丙基-N,N-二甲基(2-羟基)磺丙基甜菜碱这两种新型甜菜碱类两性表面活性剂。通过紫外、红外及质谱分析,对目标产物进行了结构表征,并对其表面张力和临界胶束浓度进行了测定。     

Synthesis and evaluation of new imidazolium‐based aromatic ether functionalized cationic mono and gemini surfactants

Synthesis of a novel series of imidazolium‐based surfactants, [(ROArCH₂MIm)Br] with aromatic ether functionalized hydrophobic tail of varying chain lengths and also their gemini counterparts were conducted in the present work. Synthesis involves initial conversion of 4‐hydroxy benzoic acid to its methyl ester followed by its O‐alkylation with long chain fatty alcohols, which was subsequently reduced and brominated to get 4‐alkyloxy benzyl bromide. For the synthesis of monocationic surfactant, 4‐alkyloxy benzyl bromide is quaternized with N‐methylimidazole. Gemini surfactants are synthesized by initial coupling of imidazole to 4‐alkyloxy benzyl bromide followed by its quaternization with dibromoalkane. The surface properties of all the synthesized surfactants were determined using surface tensiometry. Within the same homologous series, expected decrease in critical micelle concentration (cmc) with the increase in hydrophobicity was observed for shorter chain homologs. However, the deviation in cmc value from regularity was observed when the number of carbon atoms in the hydrophobic chain exceeded a certain number. The cmc values of the geminis were found to be remarkably low compared to their monomeric counterparts.     

Critical micelle concentrations of ternary surfactant mixtures: Theoretical prediction with user-friendly computer programs and experimental design analysis

We studied the behavior of an aqueous ternary surfactant mixture composed of a nonionic surfactant and two anionic surfactants which differ in both surfactant hydrophobic tail length and surfactant hydrophilic head structure. We used an experimental design program to calculate the critical micelle concentrations (CMCs) of this ternary surfactant mixture over the entire range of solution compositions. As inputs, the experimental design methodology requires the values of the ternary surfactant mixture CMCs for a limited subset of solution compositions which is determined by the experimental design program. We showed that this subset of ternary surfactant mixture CMC values can either be measured experimentally or predicted theoretically. The theoretical CMCs were predicted by a series of userfriendly computer programs which are based on molecular-ther-modynamic theories describing single and mixed micelle formation. The experimental design program generated two surfaces describing the ternary surfactant mixture CMCs over the entire solution composition range—one based on the experimentally measured subset of CMC values, and the other based on the theoretically predicted CMC values for the same subset of solution compositions. We found that these two CMC surfaces agree very well, thus demonstrating the utility of the computerassisted molecular-thermodynamic modeling as a predictive tool in surfactant mixture characterization and design.     

Wettability alteration and reducing water blockage in tight gas sandstone reservoirs using mixed cationic Gemini/nonionic fluorosurfactant mixtures

The unrecovered hydraulic fracturing fluid will invade the matrix and induce water blockage, creating formation damage and hindering the oil or gas production rate. First, the synergistic effect of cationic Gemini surfactant (MQAS) and nonionic fluorosurfactant (N-2821) mixtures on reducing the surface tension and wettability alteration was investigated in this paper. The critical micelle concentration (CMC) of the surfactant mixture is one or two orders of magnitude lower than that of N-2821 and MQAS, indicating that the MQAS/N-2821 mixtures exhibit an apparent synergistic effect in reducing surface tension. Moreover, the maximal contact angle of MQAS/N-2821 mixtures reached 83.55° at α_N-2821 = 0.5, and the total surfactant concentration of 1 × 10⁻⁴ mol/L due to the adsorption of surfactant. The adsorption mechanism of surfactants on the surface of quartz sand was then examined. The adsorption kinetics is consistent with the pseudo-second-order model at different surfactant concentrations, while the Freundlich model is suitable for describing the adsorption behavior of surfactants on the sandstone surface. This finding indicates that surfactant adsorption is multilayered. The MQAS/N-2821 surfactant mixtures have excellent surfactant activity due to the relationship of the capillary pressure to the surface tension, pore radius, and contact angle; thus, the addition of surfactant mixtures can reduce the liquid saturation effectively. Furthermore, the sequential imbibition experiments indicate that MQAS/N-2821 mixtures alter the wettability of the core plug, which results from the adsorption of surfactants. Compared with brine water, the MQAS/N-2821 mixtures decreased the liquid saturation and increased the permeability recovery ratios of the core plug.