Ionic Liquid Surfactant Research Articles

Comparison Between Phase Behavior of Gemini Imidazoliums and Monomeric Ionic Liquid Surfactants in W/O Microemulsion Systems

The composition and structural parameters of W/O microemulsions containing gemini surfactant 1,4-bis(3-dodecylimidazolium-1-yl)butane bromide [C12(Bim)2-2Br] and W/O microemulsions containing ionic liquid type surfactant 1-dodecyl-3-methylimidazolium bromide (C12mimBr) were studied and compared at different molar ratios of water to surfactant (ωo). The mole fractions of the alcohol in the interfacial layer in C12(Bim)2-2Br-based systems are always larger than that in C12mimBr-based systems. However, the mole fractions of the alcohol in the oil phase are nearly the same for both the systems. The C12(Bim)2-2Br-based systems have greater absolute values of the Gibbs energy (−ΔG o o→i ) than that of C12mimBr-based systems. In the C12(Bim)2-2Br-based systems, a large number of cosurfactants at the interfacial layer is conducive for the formation of a smaller droplet. The effects of alcohols, alkanes, and salinity on the composition and structural parameters of the two systems were also investigated and discussed.

Structural and functional stability of cellulase in aqueous-biamphiphilic ionic liquid surfactant solution.

In order to explore the potential of a biamphiphilic ionic liquid surfactant as an enzyme stabilizer in detergents, we have investigated the structural and functional stability of cellulase upon interaction with 3-methyl-1-octylimidazolium dodecylsulfate, [C8mim][C12OSO3], in aqueous medium at pH 4.8. Adsorption and binding isotherms determined from tensiometry and isothermal titration calorimetry indicated that [C8mim][C12OSO3] interacts with cellulase distinctly at the three critical concentrations, viz., aggregation, C1, saturation, C2, and vesicular, C3. Fluorescence (at λex = 280 nm), far UV-circular dichroism spectra, and dynamic light scattering results have shown that [C8mim][C12OSO3] alters the tertiary and secondary structure of cellulase with a slight initial unfolding in the monomeric regime (up to C1), refolding in the aggregation regime (up to C2), and unfolding in the shared aggregation regimes (below C3) and stabilizes the altered conformation in the post-vesicular regime with an overall variation of hydrodynamic diameter from 4.12 to 7.19 nm. A dinitrosalicylic acid sugar assay test showed excellent functional stability of cellulase with an activity of ≥1 unit/mg in all the concentration regimes. A very good surface activity (J. Phys. Chem. B 2012, 116, 14363) complied by the present results vindicates the candidature of [C8mim][C12OSO3] as a potential alternative of mixed micelles or nonionic surfactants for cellulase stabilization in detergent industries.

Combined use of chiral ionic liquid surfactants and neutral cyclodextrins: Evaluation of ionic liquid head groups for enantioseparation of neutral compounds in capillary electrophoresis

Cyclodextrins (CDs) are most commonly used chiral selectors in capillary electrophoresis (CE). Although the use of neutral CDs and its derivatives have shown to resolve plethora of charged enantiomers, they cannot resolve neutral enantiomers. The use of ionic liquids (ILs) surfactants forming successful complex with CDs present itself an opportunity to resolve neutral enantiomers. In this work, the effect of IL head groups and their complexation ability with heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) was studied for the separation of neutral enantiomers by CE. First, cationic IL type surfactants with different chiral head groups were synthesized. Physicochemical properties such as critical micelle concentration were determined by surface tension, whereas aggregation and polarity were determined by fluorescence spectroscopy. The complexation ability of ILs with TM-β-CD was characterized in the gas phase by CE-mass spectrometry. The influence of the type of ILs head group and its concentration on chiral resolution, resolution per unit time and selectivity were investigated for four structurally diverse neutral compounds. The binding constants of the neutral analytes to the IL–CD complex were estimated by y-reciprocal method. The hydrophobicity of the side chain of the IL head group displayed significant effect on the binding constants and enantioseparations.

CO2 capture with complex absorbent of ionic liquid, surfactant and water

A new kind of high efficiency and low cost CO2 complex absorbent was studied. Through innovative research, imidazolium-based ionic liquid was mixed with an aqueous solution of a non-ionic surfactant. The absorption ability of each complex absorbent with different concentrations was tested under a condition of 20°C, from 0.1 to 0.6MPa. The absorption capacity of CO2 in absorbents increases with increasing pressure and concentrations of ionic liquids. Different aqueous ionic liquid–surfactant solutions had different CO2 absorption, and the sequence was as follows: X-100>TWEEN 80>PEG 400. [emim] [OTf] was more likely to absorb CO2 than the other four ionic liquids. All of the complex absorbents had good absorption properties. The best combination was made up of 5% TWEEN 80, 10% [emim] [OTf] and water, which could capture 0.798molL−1 CO2 at 0.6MPa while pure water could only capture 0.439molL−1 under the same conditions. Through computer numerical simulations, the experimental data could be well fitted with Henry’s law and Langmuir isothermal adsorption equation. After multiple absorption and regeneration, the absorption capacity of the complex absorbent was reduced by less than 5%. It could be expected to be a new type of CO2 capture absorbent.

Self-aggregation of cationic dimeric surfactants in water–ionic liquid binary mixtures

The micellization of four dimeric cationic surfactants (“gemini surfactants”) derived from N-dodecyl-N,N,N-trimethylammonium chloride was studied in pure water and in water–ionic liquid (IL) solutions by a wide range of techniques. The dimeric surfactants are distinguished by their rigid spacer groups separating the two surfactant motifs, which range from C3 to C5 in length. In order to minimize organic ion pairing effects as well as the role of the ionic liquids as potential co-surfactants, ILs with inorganic hydrophilic anions and organic cations of limited hydrophobicity were chosen, namely ethyl, butyl, and hexyl-3-imidazolium chlorides. 1H NMR two-dimensional, 2D, rotating frame nuclear Overhauser effect spectroscopy measurements, ROESY, supported this premise. The spacer nature hardly affects the micellization process, neither in water nor in water–IL solutions. However, it does influence the tendency of the dimeric surfactants to form elongated micelles when surfactant concentration increases. In order to have a better understanding of the ternary water–IL surfactant systems, the micellization of the surfactants was also studied in aqueous NaCl solutions, in water–ethylene glycol and in water–formamide binary mixtures. The combined results show that the ionic liquids play a double role in the mixed systems, operating simultaneously as background electrolytes and as polar organic solvents. The IL role as organic co-solvent becomes more dominant when its concentration increases, and when the IL alkyl chain length augments.

Effect of protic ionic liquid and surfactant structure on partitioning of polyoxyethylene non-ionic surfactants.

The partitioning constants and Gibbs free energies of transfer of poly(oxyethylene) n-alkyl ethers between dodecane and the protic ionic liquids (ILs) ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) are determined. EAN and PAN have a sponge-like nanostructure that consists of interpenetrating charged and apolar domains. This study reveals that the ILs solvate the hydrophobic and hydrophilic parts of the amphiphiles differently. The ethoxy groups are dissolved in the polar region of both ILs by means of hydrogen bonds. The environment is remarkably water-like and, as in water, the solubility of the ethoxy groups in EAN decreases on warming, which underscores the critical role of the IL hydrogen-bond network for solubility. In contrast, amphiphile alkyl chains are not preferentially solvated by the charged or uncharged regions of the ILs. Rather, they experience an average IL composition and, as a result, partitioning from dodecane into the IL increases as the cation alkyl chain is lengthened from ethyl to propyl, because the IL apolar volume fraction increases. Together, these results show that surfactant dissolution in ILs is related to structural compatibility between the head or tail group and the IL nanostructure. Thus, these partitioning studies reveal parameters for the effective molecular design of surfactants in ILs.

Self-assembly of new surface active ionic liquids based on Aerosol-OT in aqueous media

New anionic ionic liquid surfactants have been synthesized by replacing the sodium cation of Aerosol-OT (sodium dioctylsulfosuccinate, [Na]AOT) with various biocompatible moieties, such as 1-butyl-3-methyl imidazolium ([C4mim]), proliniumisopropylester ([ProC3]), cholinium ([Cho]), and guanidinium ([Gua]). The Aerosol-OT derived ionic liquids (AOT-ILs) were found fairly soluble in water and formed vesicles above a critical vesicle concentration (CVC) which depended upon the nature of cation, and followed the order: [ProC3]<[C4mim]<[Gua]<[Cho]<Na+. The self-assembly process was characterized using surface tension (ST), isothermal titration calorimetry (ITC), conductivity, dynamic light scattering (DLS), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). Unlike other AOT-ILs, a structural transformation has been observed for [C4mim]AOT above CVC, because of certain amphiphilic character in the cation [C4mim]. Thermodynamic parameters calculated from ITC and conductivity techniques revealed that the vesicle formation process is entropy driven for [C4mim]AOT, whereas the process is both enthalpy and entropy driven for other AOT-ILs. In order to check the versatility of synthesized AOT-ILs we have tested their dissolution behavior in a different class of ionic liquids. All the AOT-ILs were found fairly soluble in the hydrophilic IL, ethanolammonium formate (EOAF), whereas only [C4mim]AOT and [ProC3]AOT were found soluble in hydrophobic IL, [C4mim]Tf2N. Such combinations can have potential for construction of stable colloidal formulations or microemulsions in ionic liquid media.

Flame retardancy and mechanical properties of polyamide 6 with melamine polyphosphate and ionic liquid surfactant‐treated montmorillonite

ABSTRACTThe mechanical properties and inflammability of polyamide 6 (PA6) nanocomposites incorporated with Montmorillonite organoclay (MMT) modified with thermal stable ionic liquid surfactants were investigated. The compatibility between ionic liquid‐treated MMT and PA6 matrix was improved and the intercalation morphology was achieved, which resulted in the increaseof tensile modulus. However, the addition of organo‐MMTs alone did not improve the inflammability of the PA6 nanocomposite, because of strong melt‐dripping behavior of PA6 matrix. Addition of auxiliary melamine polyphosphate (MPP) intumescent flame retardant to the nanocomposite prevented the melt dripping and enhanced inflammability performance. The enhanced inflammability of PA6/organoclay/MPP nanocomposites was attributed to the synergistic effect between imidazolium or phosphonium organo‐MMTs and intumescent flame retardant MPP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40648.

Structural Variation in Polyoxomolybdate Hybrid Crystals Comprising Ionic-Liquid Surfactants

Polyoxomolybdate inorganic-organic hybrid crystals were synthesized with 1-decyl-3-methylimidazolium and 1-dodecyl-3-methylimidazolium as ionic-liquid surfactants. Both hybrid crystals possessed alternate stacking of surfactant layers and octamolybdate (Mo8) monolayers, while the molecular structures of Mo8 were different depending on the surfactants and solvents employed for crystallization. Each Mo8 anion was connected by two sodium cations to form infinite one-dimensional chain. The surfactant chains in these crystals were arranged in a complicatedly bent manner, which will be induced by the weak C–H···O hydrogen bonds between the Mo8 anions and ionic-liquid surfactants.

Water/oil/[P6,6,6,14][NTf2] phase equilibria

Phase equilibria data for complex systems (more than three components or two phases, high pressures, complex fluids…) are needed to develop thermodynamic models capable of correlating and predicting their behaviour. Along these lines, systems composed of water, oil and surfactant exhibit an interesting conduct. In this work, the (liquid+liquid) equilibria of a ternary system comprising water, n-dodecane and a surfactant ionic liquid, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, have been determined at temperatures (298.15 or 348.15)K and atmospheric pressure. Winsor type III systems have been found without the need of adding any co-surfactant. The stability of the triphasic system with temperature has been tested. Some physical properties (density, viscosity and interfacial tension) for phases involved have been also determined. As expected, a minor surfactant character has been found for this ionic liquid rather than for the homologous with the chloride anion.

Mixed system of ionic liquid and non-ionic surfactants in aqueous media: Surface and thermodynamic properties

The mixed system of ionic liquid (IL) tetraethyl ammonium tetrafluoroborate [TEA(BF4)] and numerous ethylene oxide based non-ionic surfactants in aqueous media were studied using surface tension, viscosity and dynamic light scattering (DLS) measurements. Various surface properties like critical micelle concentration (cmc), maximum surface excess concentration (Γmax), minimum surface area per surfactant molecule (Amin), surface tension at the cmc (γcmc), adsorption efficiency (pC20), and effectiveness of surface tension reduction (πcmc) as well as thermodynamic parameters of micellization have been determined. DLS and viscosity measurements revealed that the micellar growth was attributed to the bridged solvophilicity of the POE chain in surfactants at elevated temperatures. In most of the cases, the progression ensues from exothermic to endothermic with increase in temperature of the mixed system. Thermodynamic parameter indicates that the micelle formation process is enthalpy driven at low temperature and entropy driven at higher temperature.

Study on Surface Tension and Displacement Efficiency of Ionic Liquid Surfactants Containing Amine Functional Groups

Description is given to preparation of three ionic liquid surfactants containing amine functional groups, characterization of their functional groups using the infrared spectrometer, determination of their surface tension and the oil displacement test in this paper to investigate the effect of alkane branch chains with different carbon numbers on the surface tension and the displacement efficiency. The result shows that, the surfactants exhibit the structural characteristic of the ionic liquid as the characteristic absorption peaks occur on C-N and C-H of the imidazole rings at the wave numbers of 1338cm-1, 1234cm-1, 1465cm-1 and 3142cm-1, respectively. The surface tension isothermal curves and the oil displacement test proved that the ionic liquid imidazole surfactants with shorter-chain groups are more active on surface, with the minimal surface tension up to 32.5 mN/m, and led to higher displacement efficiency, increasing by 3.3% at the concentration of 1000mg/L compared with the water flooding.

Porating Anion-Responsive Copolymeric Gels

A polymerizable ionic liquid surfactant, 1-(11-acryloyloxyundecyl)-3-methylimidiazolium bromide (ILBr), was copolymerized with methyl methacrylate (MMA) in aqueous microemulsions at 30% (ILBr w/w) and various water to MMA ratios. The ternary phase diagram of the ILBr/MMA/water system was constructed at 25 and 60 °C. Homopolymers and copolymers of ILBr and MMA were produced by thermally initiated chain radical microemulsion polymerization at various compositions in bicontinuous and reverse microemulsion subdomains. Microemulsion polymerization reaction products varied from being gel-like to solid, and these materials were analyzed by thermal and scanning electron microscopy methods. Microemulsion polymerized materials were insoluble in all solvents tested, consistent with light cross-linking. Ion exchange between Br(-) and PF6(-) in these copolymeric materials resulted in the formation of open-cell porous structures in some of these materials, as was confirmed by scanning electron microscopy (SEM). Several compositions illustrate the capture of prepolymerization nanoscale structure by thermally initiated polymerization, expanding the domain of compositions exhibiting this feat and yet to be demonstrated in any other system. Regular cylindrical pores in interpenetrating ILBr-co-MMA and PMMA networks are produced by anion exchange in the absence of templates. A percolating cluster/bicontinuous transition is "captured" by SEM after using anion exchange to visualize the mixed cluster/pore morphology. Some design principles for achieving this capture and for obtaining stimuli responsive solvogels are articulated, and the importance of producing solvogels in capturing the nanoscale is highlighted.

Polyoxomolybdate–Surfactant Layered Crystals Derived from Long-tailed Alkylamine and Ionic Liquid

Abstract Polyoxomolybdate inorganic–organic hybrid crystals were synthesized by using long-tailed primary amine and ionic-liquid surfactants. Dodecylamine and 1-dodecyl-3-methylimidazolium bromide were employed for the syntheses. Both hybrid crystals contained a β-type octamolybdate (Mo8) anion and showed alternate stacking of Mo8 monolayers and interdigitated surfactant bilayers. The arrangement of Mo8 layers in the inorganic monolayers was different between the hybrid crystals because of the difference in the structures of the surfactant hydrophilic head.

Synthesis of Novel Cationic Copolymer Acrylamide/Acrylic Acid Ester by Single Electron Transfer Living Radical Polymerization in Aqueous Solution

The imidazole,acrylonitrile,bromooctane were used to synthesize a new cationic polymerizable ionic liquid surfactant named chlorinated-1-octyl-3-(4-butylacrylate-based) imidazole(PMOIH8).Using 2-chloropropylamide(MPC) as the initiator,Cu0 powder and tris-(2-dimethylamino ethyl) amine(Me6-TREN) as the catalyst,a new kind of copolymer acrylamide/acrylic ester was synthesized via single electron transfer living radical polymerization(SET-LRP) of acrylamide with PMOIH8.The resulting polymers were analyzed by FT-IR,MS and 1H NMR,and the results showed that the polymers were target products.The relative molecular mass and the distribution of the resulting polymer were determined by GPC.The relative molecular mass of polymers is within the ramge of 2 × 103 ～ 14 × 103,and the relative molecular mass distribution is within the range of 1.21 ～ 1.75.Various factors which might affect the SET-LRP such as catalyst and initiator were discussed.The results showed that as the amount of catalyst reduced,the polymerization rate decreased and the polymerization rate constant(kapp p) reduced from 0.0168 min-1 to 0.0065 min-1,while the relative molecular mass distribution M w/ Mn increased from 1.25 ～ 1.71 to 1.32 ～ 1.75,and the initiator efficiency decreased,Ieff = 90.24%.As the amount of initiator increased,the relative molecular mass distribution of the resulting polymer was narrower with Mw/ Mn reduced from 1.25 ～ 1.71 to 1.21 ～ 1.68,while the polymerization rate constant(Kapp p) increased from 0.0168 min-1 to 0.0201 min-1,and the initiator efficiency increased,Ieff = 93.17%.

Nonaqueous Microemulsions Based on N,N′-Alkylimidazolium Alkylsulfate Ionic Liquids

The ternary system composed of the ionic liquid surfactant (IL-S) 1-butyl-3-methylimidazolium dodecylsulfate ([Bmim][DodSO4]), the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]), and toluene has been investigated. Three major mechanisms guiding the structure of the isotropic phase were identified by means of conductometric experiments, which have been correlated to the presence of oil-in-IL, bicontinuous, and IL-in-oil microemulsions. IL-S forms micelles in toluene, which swell by adding RTIL as to be shown by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) experiments. Therefore, it is possible to form water-free IL-in-oil reverse microemulsions ≤10 nm in size as a new type of nanoreactor.

Mixed Micellization and Surface Properties of Ionic Liquids/Triton X-100 Mixture System in Aqueous Media

Abstract Two binary systems of nonionic surfactant Triton X-100 and imidazolium ionic liquid surfactants with different carbon chain: C12mimBr (1-dodecyl-3-methylimidazolium bromide) and C14mimBr (1-tetradecyl-3-methylimidazoliumbromide) have been studied in this paper. The micellization and surface properties of the binary systems were determined by surface tension and conductivity methods, respectively. The critical micelle concentration (CMC), the maximum surface excess (Γmax), minimum area per molecule (Amin) and surface pressure at the CMC (ΠCMC) of single and mixed systems were obtained. Rubingh's theory was used to calculate the composition of the mixtures, and the molecular interaction parameter β. Negative value of β indicates synergism in mixed micelle formation. The order of absolute value of β and average β: C12mimBr/Triton X-100 &gt; C14mimBr/Triton X-100. The values of ΔG0 m and ΔG0 ads have also been calculated, and both of them were found to be negative in all pure and mixed surfactants, indicating the spontaneity of micellization and adsorption of the surfactants.

Facile synthesis of calcium carbonate with an absolutely pure crystal form using 1-butyl-3-methylimidazolium dodecyl sulfate as the modifier

Calcium carbonate (CaCO3) nanocrystals with controllable polymorph and morphology have been successfully synthesized with the aid of an effective control agent, a halogen-free, low-cost ionic liquid surfactant, 1-butyl-3-methylimidazolium dodecylsulfate ([C4mim][C12SO4]) in a supersaturated aqueous solution. For the first time, facile preparation of pure lens-like vaterite, sheet-like calcite, and peanut-like aragonite was all achieved in the [C4mim][C12SO4] aqueous solution through changing the concentration, temperature, and initial pH value and adding magnesium ions. Washed by water and ethanol, all the aggregates were free of [C4mim][C12SO4] and can be stable at least 1 month in air. The crystal form of the aggregates changed from pure calcite to pure vaterite at room temperature only through increasing [C4mim][C12SO4] concentration. Formation of the ordered CaCO3 structures is mainly ascribed to the aggregation of the primary nanoparticles whose formation mechanism is related to the change of supersaturation. This study can provide a facile and environment-friendly method to fabricate CaCO3 crystal aggregates with various morphologies and polymorphs and can be used for large-scale industrial production and biomimetic synthesis.

Ionic liquids as surfactants in micellar liquid chromatography

This paper is devoted to application of ionic liquids as surfactants in LC of organic compounds, derivatives of 1,4-thiosemicarbazides. According to HPLC requirements the most advantageous conditions such as transparency for ultraviolet light, low CMC, additional inorganic salt additives, and appropriate organic solvent were established. The CMC was determined using conductivity measurements. Suitability of two different stationary phases: RP-C18 and cyanopropyl bonded phase was examined under micellar conditions. Chosen ionic liquid surfactant was compared to common traditional amphiphilic reagent - SDS. Elaborated on chromatographic micellar conditions were tested as a pilot technique for prediction of distribution coefficients of organic analytes in ionic liquid-based aqueous two-phase system.

Charge Screening between Anionic and Cationic Surfactants in Ionic Liquids

The aggregation and interfacial behavior of mixtures of anionic (sodium dodecylsulfate, SDS) and cationic (dodecylammonium bromide, DTAB) surfactants were investigated. A room-temperature ionic liquid (IL) was explored as a solvent for the SDS/DTAB system and compared to water. The critical micelle concentration (cmc) and composition in mixed micelles were determined for both solvents. Our experiments showed nearly ideal mixing of SDS/DTAB over the entire composition range and suggest that charge screening is prominent in ILs. This behavior is in sharp contrast to the strong electrostatic attraction and a multiphase composition gap in water. Two models by Clint and Rubingh, which describe ideal and nonideal micellar behavior, respectively, are discussed on the basis of our results. According to Rubingh's model, the composition of mixed micelles is gradually changing with the bulk composition in ILs but tends to be a 1:1 ratio in water. The results here are further support of the strong charge screening in ionic liquids.