Gemini Surfactants In Aqueous Solution Research Articles

New long tail gemini surfactant in aqueous solution: Self-assembly, rheological properties and responsiveness to hydrocarbon

Gemini surfactants are promising to replace conventional monomeric surfactants in various applications. In this paper, a new gemini surfactant with long unsaturated oleyl tails and bis(hydroxyethyl) ammonium head groups linked by butyl spacer was synthesized. Its critical micelle concentration in salt-free water (12 µM) is much lower than for its monomeric analog (220 µM). Without any additives this surfactant can form viscoelastic solutions with the viscosity of up to 1 kPa·s and elastic modulus of 15 Pa at the conditions, when the viscosity of the single-chained monomeric analog is close to that of pure water. These are one of the highest values reported so far for C18-tailed gemini surfactants without additives. The structure of the gemini surfactant solutions was studied by cryo-TEM and SAXS. Cryo-TEM revealed the presence of closed-looped micelles coexisting with linear wormlike micelles as well as the regular spacing between the micelles arising from strong electrostatic repulsion between them. The SAXS curves were well-fitted by a form-factor of core–shell cylinder, which yielded the radius of the core and the thickness of the shell equal to 1.4 nm each. Addition of n-decane induced the drop of viscosity by 6 orders of magnitude accompanied by the transformation of wormlike micelles into microemulsion droplets with 4.4 nm radius. Such gemini surfactants providing high viscoelasticity to aqueous solution that is responsive to added hydrocarbon are promising for the application in oil recovery as thickeners of fracturing fluids that can be cleaned up without any breakers at the backflow of oil.

Synthesis, physicochemical property, and antibacterial activity of novel nonionic 1-alkylaminoglycerol Gemini surfactants

Four novel nonionic 1-alkylaminoglycerol Gemini surfactants, represented by m-s-m (m = C8 and C12, s = 3 and 4), were synthesized through a two-step reaction in high yields, and confirmed by 1H NMR, 13C NMR, and HRMS. The synthesized Gemini surfactants exhibited low CMC (1.41–5.25 mmol/L), excellent surface-tension-reducing ability (25.45–26.83 mN/m), and wetting ability on hydrophobic interface. Gemini surfactants in aqueous solutions were in stable nanoscale dispersion, and exhibited strong and long-lasting foaming ability and emulsifying abilities for benzene/water and triacylglyceride/water systems. Especially, 12–4-12 solution displayed excellent tolerance to wide pH range and high salinity. Biological evaluation demonstrated that these Gemini surfactants, except for 8–4-8, showed significant antibacterial activities against Staphylococcus aureus and Escherichia coli at 25 and 50 µg/mL. Hence, these Gemini surfactants have the potential to be used in a varieties of fields as highly efficient agents.

Synthesis and Aggregation of Novel Sugar-based Gemini Surfactants in Aqueous Solution

Abstract Novel sugar-based gemini surfactants with a 1,3-propan-2-ol spacer (1, 3-(N- alkyl-2-D-glucosaminyl acetyl) propan-2-ol, Glu(n)-3(OH)-Glu(n), n = 12, 14) were synthesized with D-(+)-glucono-1,5-lactone as starting material in two steps, whose structures were confirmed using proton nuclear magnetic resonance spectroscopy (1H NMR) and carbon nuclear magnetic resonance carbon spectroscopy (13C NMR). The micellization of Glu(n)-3(OH)-Glu(n) (n = 12, 14) in aqueous solution at 25.0°C was investigated by using surface tension measurement. The results show that the critical micelle concentration (CMC) of Glu(12)-3(OH)-Glu(12) is around 10–5 mol × L–1, and is one order of magnitude smaller than that of Glu(14)-3(OH)-Glu(14), indicating that the surface activity of Glu(12)-3(OH)-Glu(12) is superior to that of Glu(14)-3(OH)-Glu(14). Moreover, the aggregation behavior of Glu(12)-3(OH)-Glu(12) in aqueous solution at different pH values was investigated by surface tension, dynamic light scattering (DLS), and cryogenic transmission electron microscopic (Cryo-TEM) measurements. The results indicate that the CMC slightly increases with the decrease of the solution pH. The microstructure of Glu(12)-3(OH)-Glu(12) aggregates transitions from micelle to vesicle with the solution pH from acidic to neutral and alkaline. The microstructural transformation of Glu(12)-3(OH)-Glu(12) with the solution pH is mainly determined by the protonation of the two tertiary amine nitrogen atoms in its hydrophilic headgroups.

Synthesis and Aggregation Behavior of Jellyfish-Shaped Triazine Hexamer Quaternary Ammonium Chloride Surfactant

A novel jellyfish-shaped triazine hexamer quaternary ammonium chloride surfactant (TH12QC) was synthesized, which consisted of one triazine spacer group and six long flexible hydrophobic chains. The molecular structure and aggregation behavior of TH12QC was investigated by nuclear magnetic resonance (NMR), surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscope (TEM), etc. The results show that the jellyfish-shaped TH12QC has better surface activity and lower surface tension than traditional ionic and Gemini surfactants in aqueous solution. There are two inflection points in the curve of conductivity versus concentration of the TH12QC aqueous solution, which correspond to the critical aggregation concentration (CAC) and the critical micelle concentration (CMC) respectively. The existence of CAC indicates that there is a pre-aggregation process before TH12QC forms micelles. The results of DLS and TEM show that network pre-aggregation, spherical aggregation and dense spherical aggregation were observed in different concentration of TH12QC aqueous solution, and the electrostatic equilibrium of the system subtly depends on the concentration of the solution. In addition, intramolecular and intermolecular hydrogen bonding is also an important factor. This study provides a method for studying the aggregation behavior and morphology of oligomeric surfactants with rigid spacer groups.

Investigation of Mixing Behavior of both a Conventional Surfactant and Different Inorganic Salts with a Cationic Gemini Surfactant in Aqueous Solution

AbstractN,N′‐bis [3‐(dodecanoylamino)propyl]‐N,N,N′,N′‐tetramethylhexane‐1,6‐diaminium dibromide is a cationic Gemini surfactant including quaternary ammonium salt with amide groups. Critical micelle concentration (CMC) and some thermodynamic parameters of the cationic Gemini surfactant were investigated using surface tension and conductivity methods. Mixed micellization of binary mixtures of the cationic Gemini surfactant with a conventional surfactant cetyl trimethylammonium bromide (CTAB) was investigated using the conductometric method at five different temperatures ranging from 303.15 to 323.15 K. CMC, micellar ionization degree (αm), counterion binding constant (g1), interaction parameter (β), and activity coefficients ( and ) of mixed systems were found out from data of conductivity at different mole fractions for all studied temperatures. Additionally, the effects of some inorganic salts with different concentrations on the surface properties of cationic Gemini surfactant were examined by surface tension measurements. Some surface properties of the pure cationic Gemini surfactant and mixed salts systems were calculated using the data of surface tension.

Effects of Molecular Structure and Temperature on Micellization of Cationic Ammonium Gemini Surfactants in Aqueous Solution

AbstractMicellization of four cationic quaternary ammonium gemini surfactants, having a diethyl ether or hexyl spacer with the alkyl chain lengths of 12 and 16 carbon atoms, was studied using isothermal titration microcalorimetry (ITC) and electrical conductivity measurements in the temperature range from 298.15 to 313.15 K. In this temperature range, where surfactants are normally applied, the temperature almost does not influence the critical micelle concentration (CMC) and the degree of micelle ionization (α) values of the gemini surfactants, and the replacement of a hexyl spacer by a diethyl ether spacer leads to a slight decrease in the CMC and α values. However, as the alkyl chain length increases from 12 to 16 carbon atoms, the CMC values significantly decrease from 0.99–1.19 mM to 0.020–0.057 mM. In particular, the enthalpy of micellization (ΔHmic) and the associated thermodynamic parameters show obvious changes with varying temperature and molecular structure. ΔHmic becomes much more exothermic at higher temperature or for the surfactants with a more hydrophilic spacer. Moreover, the heat capacity change of micellization (ΔC P, mic) is less exothermic for the surfactants with a more hydrophilic spacer or a longer alkyl chain. The enthalpy–entropy compensation data show that the surfactants with longer alkyl chains have a more stable micellar structure.

Temperature controlled comparative physico-chemical studies of DTAB and 12-2-12 Gemini surfactants in aqueous solutions of fructose, maltose and raffinose

The Micellar behaviour of synthesised cationic Gemini surfactant ethanediyl-1,2-bis (dimethyldodecylammonium bromide) and its single-chain counter-part i.e., Dodecyltrimethylammonium bromide (DTAB) in absence and presence of carbohydrates (fructose, maltose and raffinose) has been investigated. The conventional technique viz. surface tension measurements over a wide range of temperature, (293.15–313.15K with an interval of 5K) and spectroscopic method i.e. fluorescence probe at room temperature have been employed to determine critical micelle concentrations (CMC's) of both the surfactants. The decrease in CMC have been found for both the studied surfactants; however the effect being more prominent in case of Gemini surfactant (GS). From surface tension data, various interfacial parameters have been evaluated that reflects the presence of stronger electrostatic attractions between carbohydrates and the micelle of surfactants. The CMC values calculated using both the studies have been found to be in good agreement and corroborate each other's observations.

Clear distinction between CAC and CMC revealed by high-resolution NMR diffusometry for a series of bis-imidazolium gemini surfactants in aqueous solutions.

The aggregation behavior in the transition region was studied for a series of dicationic surfactants 3,3′-[α,ω-(dioxaalkane)]bis(1-dodecylimidazolium)dichlorides with varied spacer length from two to twelve carbon atoms. We employed Nuclear Magnetic Resonance diffusometry and Bayesian DOSY analysis to obtain the aggregate size distribution in the transition region. The critical concentrations CC were independently obtained from surface tension, electric conductivity, UV-Vis and NMR methods. The micelle aggregation numbers were estimated from the self-diffusion coefficients and were independently confirmed using steady-state fluorescence quenching. The morphology of the aggregates was characterized by small-angle scattering of synchrotron radiation and molecular dynamics simulations. The obtained CC values are identified as critical aggregation concentrations CAC. A broad transition region was observed, and stable micelles were obtained at much higher concentrations than CAC. The accurate CMC values could not be identified for the systems in the study. We indicated that the distribution of aggregate size becomes small and the system becomes homogeneous at much larger concentrations than CAC (typically 15–20 mM). The existence of a slow exchange between two environments, an aggregate and aqueous environment, was confirmed by 1H NMR and 2D HSQC NMR spectroscopy.

The kinetics and effect of a new gemini surfactant on the efficiency of micellar catalysis for the hydrolysis reaction of 4-nitrophenyl acetate

A new cationic gemini surfactant containing amide bond (C12-4-C12) was synthesized through a simple two-step procedure, and its chemical structure was confirmed by IR, 1H NMR spectroscopy and element analysis. The physical and chemical properties of the gemini surfactant in aqueous solution were investigated by surface tension and conductivity. The results show that the gemini surfactant possess good surface properties. The effect on the hydrolysis reaction rate constant (K) of 4-nitrophenyl acetate (PNPA) and the kinetics of the hydrolysis reaction with the gemini surfactant (C12-4-C12) was studied by means of spectrophotometry. The experimental results showed that the efficiency of micellar catalysis by gemini surfactant C12-4-C12 was significantly higher than that of the traditional single-chained surfactant CTAB. The possible liquid-liquid biphasic micellar catalyzed model was presented, which might be beneficial for the further study of the mechanism of liquid-liquid biphasic reaction.

Critical Role of the Spacer Length of Gemini Surfactants on the Formation of Ionic Liquid Crystals and Thermotropic Behavior.

Numerous reports have shown that the self-assembling properties of 12-s-12 bis(quaternary ammonium) gemini surfactants in aqueous solution are significantly influenced by s, the number of methylene groups in the covalent spacer. However, the role played by s on the phase behavior of the single compounds has not been investigated in a similarly systematic way. Here, we report on the thermotropic phase behavior of the anhydrous compounds with s = 2-6, 8, 10, and 12, resorting to differential scanning calorimetry (DSC), polarized light microscopy (PLM), and X-ray diffraction (XRD). All of the compounds show a stepwise melting behavior, decomposing at 200 °C. As the spacer length increases, nonmonotonic trends are observed for the thermodynamic parameters of the thermotropic phase transitions, mesophase formation, and solid-state d00l spacings. In particular, the number and type of mesophases (ordered smectic phases and/or fluid smectic liquid crystals) depend critically on s. Further, upon heating molecules with s < 8 decompose before the liquid phase, while those with long spacers, s = 8-12, reach the isotropization (clearing) temperature, hence forming both ionic liquid crystals and ionic liquid phases. We demonstrate that the melting behavior and type of ionic mesophases formed by gemini molecules can be usefully manipulated by a simple structural parameter like the length of the covalent linker.

Effects of 1-alkyl-3-methylimidazolium bromide ionic liquids on the micellar properties of [butanediyl-1,4-bis(dimethyldodecylammonium bromide)] gemini surfactant in aqueous solution

The micellar properties of the cationic gemini surfactant [butanediyl-1,4-bis (dimethyldodecylammonium bromide)] (12-4-12) were investigated at 298.15 K in the presence of 1-R-3-methylimidazolium bromide ionic liquids (ILs, R = 1-butyl, 1-(1-butyl)-3-methylimidazolium bromide (BuMeImBr); 1-hexyl, 1-(1-hexyl)-3-methylimidazolium bromide (HxMeImBr); and 1-octyl, 1-(1-octyl)-3-methylimidazolium bromide (OcMeImBr)), present as additives. The emphasis was on c(IL) (0.2 to 1 wt%) and the length of R. The following techniques were employed: conductivity, surface tension, UV-Vis, fluorescence spectroscopy of solubilized compounds, and dynamic light scattering (DLS). For the ILs, values of the critical micelle concentration, critical micellar concentration (cmc) of 12-4-12 decreased between 0.2 and 0.8 wt% and then increased at 1 wt%. The increased cmc may be due to the formation of mixed micelles. For (inorganic additive) NaBr, cmc decreased continuously as a function of c(NaBr). Other parameters calculated include those related to the adsorption of the surfactant at solution/air interface, micelle aggregation number, and hydrodynamic radius. ILs behave as electrolyte and cosurfactants based on c(IL).

A relative study on the micellization behavior of 12–2–12 Gemini surfactant with lactose and maltodextrin in aqueous medium: Spectroscopic and conductometric analysis

The present work reports the micellization mechanism and physico–chemical properties of synthesized 12–2–12 Gemini surfactant in aqueous solution of carbohydrates (lactose and maltodextrin) (0.0, 0.5, 1.0) % (w/v) at varying temperatures in the range (293.15–313.15) K. For this purpose, conductometric as well as spectroscopic measurements have been engaged to analyze the micellar modulation of Gemini surfactant in terms of its critical micelle concentration (CMC). The carbohydrates (lactose/maltodextrin) have been found to decrease the CMC of 12-2-12 Gemini surfactant, however, the effect is much more pronounced in maltodextrin as compared to lactose which is in compliance with the hydrophobic region present in the molecules. Further, temperature dependence of CMC has been employed to compute thermodynamic parameters of micellization in order to procure a better knowledge about the behavior of surfactant and intermolecular interactions present in such systems. The study of aqueous Gemini–carbohydrate systems may be helpful in working towards a healthier world from both personal as well as environmental aspects of life.

Structure and Rheology of Wormlike Micelles Formed by Fluorocarbon-Hydrocarbon-Type Hybrid Gemini Surfactant in Aqueous Solution.

The structure and rheological properties of wormlike micelles formed by a fluorocarbon-hydrocarbon-type hybrid gemini surfactant in an aqueous solution were investigated by means of small-angle X-ray scattering (SAXS) and viscoelastic measurements. The cross-sectional structure (the radius of the hydrophobic core and the thickness of the hydrophilic shell) and the aggregation number per unit axial length of wormlike micelles were evaluated by a model fitting analysis of SAXS profiles. Both parameters for the hybrid gemini surfactant were smaller than those of a corresponding hydrocarbon-hydrocarbon-type gemini surfactant. On the other hand, the viscosity of the hybrid gemini surfactant was higher than that of the hydrocarbon-hydrocarbon-type gemini surfactant. From the viscoelastic parameters, the steady state compliance, Je, and the terminal relaxation time, τw, which were independently obtained by dynamic viscoelastic measurement, we revealed that a larger number of entanglements and a longer contour length of the hybrid gemini surfactant led to the higher viscosity. These results obtained by the rheological measurements were consistent with those obtained by SAXS analysis.

PH reversible micelle transition of a tertiary amine-based gemini surfactant in aqueous solution

ABSTRACTIn this work, we prepared a tertiary amide-based gemini surfactant (DSTAPA), which contained two pH-sensitive tertiary amide head groups. Then the molecule state distribution and self-assembly transition of the surfactant in aqueous solution were investigated under different pH conditions. The DSTAPA molecules were on the states of double cationic (DSTAPAH2+), single cationic (DSTAPAH+), and double tertiary amine groups (DSTAPA) under acidic, neutral, and basic conditions, respectively. With the variation of the molecule states, the sample was water-like below pH of 6.8 and immediately transformed to gel-like fluid between pH of 6.8 and 7.8, then changed to white precipitate with the further increase of pH value. Furthermore, the microstructure and regulation mechanism were investigated by rheological measurements, dynamic light scattering, and cryogenic transmission electron microscopy. The appearance and micelle transitions of the DSTAPA aqueous solution are actually owing to the spherical–worm-like micelle transition, leading to dramatic viscosity increase and hydrogel formation. This transition was completely reversible and repeated for at least three cycles. Finally, a reasonable mechanism of the transition was proposed based on the viewpoints of the molecular states and micelle structures. The DSTAPA aqueous system with pH-reversible property has a great potential application in oil and gas production.

Surface Activity Properties and Aggregation Behaviors of Partially Fluorinated Gemini Surfactants in Aqueous Solution

AbstractThe surface activity and aggregation behavior of partially fluorinated gemini surfactant N,N′‐bis(3‐perfluorohexyl‐2‐hydroxypropyl)‐N,N′‐dipropanesulfonylhexylenediamine (N‐6‐Sul) was studied by surface tension, resonance light scattering and fluorescence spectra measurements. The critical micelle concentration (CMC) values obtained by the three methods are in good agreement. The surface activity parameters such as the effectiveness of surface tension reduction (Πcmc), the maximum surface excess concentration (Γmax) and the minimum surface area per molecule (Amin) were obtained through surface tension curves. The effects of pH, inorganic salts and temperature on the surface activity were also investigated. The morphology and size of the aggregates of N‐6‐Sul were examined by transmission electron microscopy (TEM). The results show that the partially fluorinated gemini surfactant N‐6‐Sul has many advantages such as high surface activity, low CMC value, great salt tolerance and temperature resistance.

Hydrophilicity and flexibility of the spacer as critical parameters on the aggregation behavior of long alkyl chain cationic gemini surfactants in aqueous solution

Abstract Series of quaternary ammonium-based gemini surfactants with long alkyl chains (C12 and C18) containing different spacers and substituents attached to the polar head group have been synthesized and their aggregation properties in aqueous solution examined. The effect of the hydrophobic chain, the nature and structure of the spacer group and the polarity of the head group on the aggregation behavior of such dimeric surfactants has been investigated. The critical micelle concentration (cmc) values of gemini surfactants in aqueous solution were determined by conductivity, steady state fluorescence and potentiometric measurements. The size of aggregates formed by investigated amphiphiles above the cmc in aqueous solution was examined by dynamic light scattering. Gemini surfactants show cmc values significantly lower than those of comparable single chain surfactants. The tendency of trimeric surfactants with a rigid spacer to form aggregates is higher than that of the corresponding dimeric surfactants. As occurs for monomeric ionic surfactants, the cmc of gemini surfactants decreases with the elongation of the hydrophobic chain. However, the effect of lengthening the alkyl chain on the cmc depends on the structure of the spacer. C12 gemini surfactants with a rigid hydrophobic spacer exhibit cmc higher than those containing a flexible hydrophobic spacer. For gemini surfactants with C18 alkyl chains this effect is even more pronounced and leads to differences in cmc values greater than one order of magnitude. The structure of the spacer, flexible or rigid chain, has been found to be a critical parameter on the self-assembly of long chain gemini surfactants. Spherical micelles are spontaneously formed above the cmc for C12 gemini surfactants, whereas trimeric and C18 gemini surfactants seems to form vesicle-like aggregates when self-aggregation occurs.

Interaction of a biosurfactant, Surfactin with a cationic Gemini surfactant in aqueous solution

The interaction between biosurfactant Surfactin and cationic Gemini surfactant ethanediyl-1,3-bis(dodecyldimethylammonium bromide) (abbreviated as 12-3-12) was investigated using turbidity, surface tension, dynamic light scattering (DLS) and small angle neutron scattering (SANS). Analysis of critical micelle concentration (CMC) values in Surfactin/12-3-12 mixture indicates that there is synergism in formation of mixed Surfactin/12-3-12 micelles. Although Surfactin and 12-3-12 are oppositely charged in phosphate buffer solution (PBS, pH7.4), there are no precipitates observed at the concentrations below the CMC of Surfactin/12-3-12 system. However, at the concentration above CMC value, the Surfactin/12-3-12 mixture is severely turbid with high 12-3-12 content. DLS and SANS measurements follow the size and shape changes of mixed Surfactin/12-3-12 aggregates from small spherical micelles via elongated aggregates to large bulk complexes with increasing fraction of Gemini surfactant.

Effect of imidazolium-based ionic liquids on the aggregation behavior of twin-tailed cationic gemini surfactant in aqueous solution

ABSTRACTMicellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C4mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C6mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C6mim][Br] and [C8mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C4mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions.

Effects of Molecular Structures on Aggregation Behavior of Gemini Surfactants in Aqueous Solutions

Effects of Molecular Structures on Aggregation Behavior of Gemini Surfactants in Aqueous Solutions

Surface and Aggregation Properties of Synthesized Cetyl Alcohol Based Bis‐Sulfosuccinate Gemini Surfactants in Aqueous Solution

AbstractA series of cetyl alcohol based anionic bis‐sulfosuccinate gemini surfactants (BSGSCA1,4; BSGSCA1,6 and BSGSCA1,8) with different spacer lengths was prepared using dibromoalkanes. The surfactant structure was elucidated using elemental analysis, Fourier transform infrared spectroscopy (FT‐IR) and nuclear magnetic resonance spectroscopy (NMR). Surface tension measurements were used to determine the critical micelle concentration (CMC), the surface tension at the CMC (γCMC), surface pressure at the CMC (πCMC) and efficiency of adsorption (pC20). On the basis of surface studies, the CMC and γCMC decreases with increasing length of the spacer group. The micelle aggregation number, determined by fluorescence quenching studies, increases with increasing surfactant concentration above the CMC. The micropolarity in the micelle increases with increasing length of the spacer and decreases with increasing surfactant concentration.