Amphiphilic Ionic Liquids Research Articles

Amphiphilic Ionic Liquids for Chemical Separation of Crude Oil Emulsions

AbstractThis work aims to synthesize novel amphiphilic ionic liquids (AILs), AH‐PM, and AD‐PM as well as apply them to chemically demulsifying crude oil emulsions. Two AILs containing different long alkyl chains were synthesized and characterized using several techniques. The surface and interfacial indicated AILs’ surface activity and ability to form micelles. For that, the demulsification efficacy (DE) of these AILs was explored using different factors affecting, e.g., AIL dose, settling time (ST), water content, and temperature. The results indicated that the AIL hydrophobicity resulting from the longer alkyl chain could improve AIL DE. Moreover, increased AIL dose, ST, water content, and temperature improved DE.

Ultra-stable ionogels based on hydrogen networks with broad temperature, environment, and long-term stability

Ionogels with broad temperature, environment, and long-term stability are desirable in intelligent flexible electronics. Herein, we have developed a novel ultra-stable ionogel through hydrogen bonding between the amphiphilic ionic liquid--1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([EMIM][NTf2]) and butyl acrylate (BA)-ethyl ethoxyethyl acrylate (EO) copolymer (P(BA-co-EO)). The ionogel demonstrates high decomposition voltage, strong adhesion stability, non-corrosive stability, and cyclic strain sensing stability (500 cycles at 120 % strain). Additionally, it exhibits broad temperature and environment adaptability, capable of stretching up to 7 times at −20 °C, maintaining consistent weight after 30 days of storage in extreme environments such as low/high temperatures (−20∼100 °C), high vacuum (6 × 10−4 Pa), and underwater (without additional sealed packaging), while also maintaining electrophysiological monitoring at −20 °C or 100 °C. Most importantly, the ionogel without sealing can self-adhere to the human skin for continuous and high-quality electrophysiological monitoring for 1 month under daily life conditions. We have utilized the ionogel to fabricate an ionic skin with multifunctional sensing capabilities for strain, pressure, and temperature, which has been successfully employed in human motion and pressure detection. It is believed that ionogels with long-term stability will pave the way for developing next-generation intelligent flexible electronics in future research endeavors.

Robust and tunable hydrogels strengthened by dynamic amphiphilic ionic domains

Hydrogels have gained increasing attentions in wearable electronics, but endure notch-sensitive and poor mechanical behavior in real-world applications. Herein, a robust and tunable hydrogel network was constructed by involving a polymerizable amphiphilic ionic liquid in polymer chains through a facile and novel strategy without additional chemical crosslinkers. The ingeniously designed dynamic amphiphilic ionic domains that are tuned by the structural domain and functional domain are crucial for reinforcing the structural integrity and allowing the polymer chains to accomplish reversible unfolding and ordered migration. The robust and functional microstructures effectively prevent crack propagation, enhancing the fracture strain (1200–2390%), tensile stress (380–1560 kPa), toughness (5–15 MJ m−3), and conductivity (0.13–0.2 mS cm−1). The obtained hydrogel acts as an excellent mechanoresponsive sensor to perceive various external stimuli to sensitively detect diverse human activities including large body motions and subtle muscle movements via electrical signals. Additionally, this strategy shows good applicable potential for preparing high-performance hydrogels based on monomers containing active double bonds, overcoming the disadvantages of poor mechanical properties of traditional free radical polymerization gels. It is anticipated that the design of dynamic amphiphilic ionic domains will provide guidance for regulating the polymer network of hydrogels and show great application potentials in real-life scenarios.

Amphiphilic ionic liquid hydrogel electrolytes with high ionic conductivity towards dendrite-free ultra-stable aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) are highly promising as large-scale energy storage devices with high capacity, safety, and low cost. However, the parasitic reaction on the of Zn anode and the growth of Zn dendrites greatly prevent the practical application of AZIBs. Here, we propose an effective strategy with hydrogel electrolytes by adding dual amphiphilic ionic liquids into acrylamide, allowing for the occurrence of the following phenomena related to the Zn anode: 1) Zn2+ preferential adsorption by the amphiphilic ionic groups to regulate the electrodeposition behavior of Zn2+ on the Zn(002) crystal surface and inhibit the growth of Zn dendrites; 2) water removal from the Zn2+ solvation sheath, reducing water activity and inhibiting side reactions; 3) improved environmental adaptability of the hydrogel electrolyte through enhancing its mechanical properties and adhesion. The obtained hydrogel electrolyte has a high ionic conductivity of 41.47 mS/cm, a highly reversible Zn plating/stripping cycle of 1400 h in Zn||Zn symmetric batteries and an enhanced electrochemical performance in Zn||NVO full batteries (94 % capacity retention at 5.0 A g−1/3000 cycles). Even under harsh conditions (10 mA cm−2/10 mAh cm−2), these cells maintained excellent cycling stability. This study provides new ideas for the practical applications of AZIBs.

Acidic ionic liquid-based liposome for efficient catalytic degradation of azo dyes

Amphiphilic ionic liquids (ILs) with an imidazole head and two undecene tails (abbreviated as [MimV11, V11]Br) were synthesized through alkylation reaction. They were utilized as lipoid monomers for constructing an isotropic catalytic degradation platform of azo dyes. The spherical structure of this IL-based liposome was reinforced by cross-linking polymerization of the olefin tails. The imidazole groups served as anchor points for attaching catalytic heteropolyanions (such as [PW12O40]3-, [PMo12O40]3-) to the liposomal vehicle. Furthermore, the arrangement of these linkers on the liposome surface facilitated the trapping and enrichment of the catalytic species. Consequently, a series of isotropic catalysts decorated with heteropolyanions (poly[MimA11, A11][heteropolyanions]) were prepared through anion exchange, where sufficiently exposed heteropolyanions maximized the catalytic degradation activity. The morphology, structure, and properties of the catalysts were confirmed using SEM, TEM, FTIR, XPS, UV–vis, and GC–MS. Experimental results found that poly[MimA11, A11][PW12O40] was the optimal catalyst, achieving a removal efficiency of 97.2% for methyl orange (MO) within 3 h. The intermediates involved in the reaction were analyzed to propose the degradation pathway of MO. Moreover, this kind of solid catalyst could be recovered by centrifugation, and its degradation efficiency remained above 91% even after five cycles. This research provides valuable insights for expanding the applications of IL-functionalized materials.

Amphiphilic ionic liquids as catalysts for efficient synthesis of novel isosorbide-based optical polymers with good biocompatibility and tunable properties

Accurate design and green synthesis of sustainable optical materials from renewable biomass has become vital in polymer science, especially in field of corneal contact lenses or intraocular lens (IOLs). Here we demonstrate the structure design of monomers and efficient synthesis of novel optical poly(isosorbide thioethers) (PITEs) with methyl, alicyclic or aromatic side-groups for high-performance biomedical optical materials. To regulate and control the polymerization process accurately, ionic liquids (ILs) were selected as catalysts and evaluated systematically. Since the presence of hydroxyl in anion improved proton-accepting ability combined with cations functionalized with dual activation sites, the IL tetraethylammonium lactate [TEA][Lac] in trace amount was discovered to show outstanding catalytic performance, better than the reported catalysts. According to experimental results, NMR analysis and DFT calculations, the anion-cation synergistic catalytic mechanism for nucleophilic hydrothiolation was proposed at molecular level. The activation barriers of transition structures decreased significantly from 211.1 to 16.7 kJ·mol−1 after using IL catalyst. The novel PITEs exhibited excellent biocompatibility for L929 cells, good optical transparency (>90 %) and higher refractive index (nD = 1.57 ∼ 1.61) than commercial IOLs (nD = 1.46 ∼ 1.55). Meanwhile, the PITEs possessed not only tunable mechanical properties (strain at break of 1.6 %∼367 %, storage modulus of 2.5 ∼ 4.3 GPa), but also suitable glass-transition temperature (Tg = 41.6 ∼ 92.9 °C) and good thermal stability for polymer melting or moulding process. This work provides a versatile approach for convenient fabrication of novel isosorbide-based polymers with adjustable properties for biomedical optical lenses, which are promising to achieve scale-up and application in future.

Effects of cationic head group structure on cytotoxicity and mitochondrial actions of amphiphilic ionic liquids

Ionic liquids (ILs) are a class of low melting point salts with physicochemical properties that make them suitable for a range of industrial applications. Accumulating evidence suggests that certain ILs are cytotoxic and potential environmental pollutants, thus understanding the structural features that promote IL cytotoxicity is important. Amphiphilic ionic liquids (AmILs), a class of ILs with lipophilic N-alkyl chains, containing aromatic head groups are generally more cytotoxic than their aliphatic counterparts, however the impact of other head group properties are less clear. This study therefore sought to provide new structure activity relationship (SAR) insights regarding the role of the cationic head group on AmIL cytotoxicity. A series of AmILs bearing a range of structurally diverse aromatic cations varying in size, charge, and lipophilicity was synthesised and screened against human MDA-MB-231 breast cancer cells. It was found that larger and more lipophilic head groups increased cytotoxicity, although the magnitude of the changes were modest. The mitochondrial effects of representative ILs were assessed. The AmILs induced mitochondrial dysfunction in MDA-MB-231 cells at cytotoxic concentrations, suggesting that they target mitochondria. The new SAR information from this study may assist in the design of AmILs with controlled cytotoxicity.

Confined amphipathic ionic-liquid regulated anodic aluminum oxide membranes with adjustable ion selectivity for improved osmotic energy conversion

To attain carbon neutrality and carbon peaking, there is an urgent need to convert the vast amount of blue energy present between seawater and river water into usable electricity. Reverse electrodialysis based on ion-exchange membranes is a promising way to efficiently achieve osmotic energy conversion. Anodic aluminum oxide (AAO) membranes are frequently used for osmotic energy harvesting because of their uniform nanopore channels, high flux, and excellent stability. However, the existing surface modification methods are complex and inefficient. In this study, an amphiphilic ionic liquid was selected to modify a porous anodic alumina membrane via simple capillary insertion. Due to the abundance of pH-dependent amphiphilic OH groups on the surface of AAO pore channels, the ionic liquids not only provide abundant surface charge but can also intelligently adjust its surface charge to different environments. In addition, it fills the AAO nanochannels to provide a continuous ion transport network. The modified hybrid membrane achieves efficient and stable osmotic energy conversion performance. This simple and feasible strategy paves the way for further improvements in commercial membranes.

Transition Mechanism from the Metastable Two-Dimensional Gel to the Stable Three-Dimensional Crystal of Imidazolium-Based Ionic Liquids.

One important quest for making high quality materials with amphiphiles is to understand how a disordered self-assembly changes to a stable crystalline state. Herein, we addressed the basic question by investigating the phase transition mechanism of imidazolium-based ionic liquid (IL) [C16mim]Br, using time-resolved small- and wide-angle X-ray scattering (SAXS-WAXS), differential scanning calorimetry, and Fourier transform infrared spectroscopy techniques. Totally, a hexagonal phase, two lamellar-gel phases, and three lamellar-crystalline phases were observed, showing the special polymorphism of the system. It was demonstrated that at low concentrations the two-dimensional gel phase (Lβ1) transforms into the most stable lamellar-crystal phase (Lc3) through two intermediate crystalline phases Lc1 and Lc2. At high concentrations, the Lβ1 phase changes to a condensed lamellar gel phase (Lβ2) before changing to Lc2 and eventually to Lc3. Comparative studies using [C16mim]Cl and [C16mim]NO3 unveiled that the interactions between the counterions and the headgroups of the IL, as well as the dehydration process, govern the nucleation process of Lc3 and thus the formation of the crystal. The in-depth investigation on the transition mechanism and the phase polymorphism in the present work advances our understanding of the crystallization of amphiphilic ionic liquids in dispersions and would promote future applications.

Self-Assembled Nanostructures in Aprotic Ionic Liquids Facilitate Charge Transport at Elevated Pressure.

Ionic liquids (ILs), revealing a tendency to form self-assembled nanostructures, have emerged as promising materials in various applications, especially in energy storage and conversion. Despite multiple reports discussing the effect of structural factors and external thermodynamic variables on ion organization in a liquid state, little is known about the charge-transport mechanism through the self-assembled nanostructures and how it changes at elevated pressure. To address these issues, we chose three amphiphilic ionic liquids containing the same tetra(alkyl)phosphonium cation and anions differing in size and shape, i.e., thiocyanate [SCN]-, dicyanamide [DCA]-, and tricyanomethanide [TCM]-. From ambient pressure dielectric and mechanical experiments, we found that charge transport of all three examined ILs is viscosity-controlled at high temperatures. On the other hand, ion diffusion is much faster than structural dynamics in a nanostructured supercooled liquid (at T < 210 ± 3 K), which constitutes the first example of conductivity independent from viscosity in neat aprotic ILs. High-pressure measurements and MD simulations reveal that the created nanostructures depend on the anion size and can be modified by compression. For small anions, increasing pressure shapes immobile alkyl chains into lamellar-type phases, leading to increased anisotropic diffusivity of anions through channels. Bulky anions drive the formation of interconnected phases with continuous 3D curvature, which render ion transport independent of pressure. This work offers insight into the design of high-density electrolytes with percolating conductive phases providing efficient ion flow.

Synthesis and Performance of Two New Amphiphilic Ionic Liquids for Demulsification of Water-in-Crude Oil Emulsions.

This work aims to synthesize and apply two novel amphiphilic ionic liquids (AILs) for the demulsification of water-in-crude oil (W/O) emulsions. To do that, 4-tetradecylaniline (TA) and 4-hexylamine (HA) were etherified using tetrethylene glycol (TEG) in the presence of bis(2- chloroethoxyethyl)ether (BE) as a cross-linker, yielding corresponding ethoxylated amines TTB and HTB. The obtained ethoxylated amines TTB and HTB were quaternized with acetic acid (AA), obtaining corresponding AILs TTB-AA and HTB-AA. The chemical structures, surface tension (ST), interfacial tension (IFT), and micelle size were investigated with various techniques. The performance of TTB-AA and HTB-AA to demulsify W/O emulsions was investigated using different influencing factors, including the demulsifier concentration, water content, salinity, and pH. Additionally, the obtained results were compared with a commercial demulsifier. The results indicated that the demulsification performance (DP) increased as the demulsifier concentration increased and the water content decreased; however, increased salinity slightly improved the DP. The data also showed that the highest DPs were achieved at a pH of 7, which suggested a change in the chemical structure of these AILs at a lower and higher pH due to their ionic structure. Furthermore, TTB-AA demonstrated higher DP than HTB-AA, which could be explained by its higher ability to reduce IFT due to a longer alkyl chain than that of HTB-AA. Furthermore, TTB-AA and HTB-AA showed significant DP compared to the commercial demulsifier especially with W/O emulsions at low water content.

Solid polymer electrolytes of ionic liquids via a bicontinuous ion transport channel for lithium metal batteries

Polymer electrolytes with bicontinuous nanostructures for lithium metal batteries were prepared by UV-polymerization of hydrophobic domains in microemulsions of ionic liquids, amphiphilic ionic liquids, lithium salts and monomers.

Aromatic long chain cations of amphiphilic ionic liquids permeabilise the inner mitochondrial membrane and induce mitochondrial dysfunction at cytotoxic concentrations

Aromatic long chain cations of amphiphilic ionic liquids (AmILs) accumulate in and permeabilise the IMM at their cytotoxic concentrations. The AmILs depolarise IMM, inhibit oxidative phosphorylation and ATP synthesis, and induce ROS formation.

Selective hydroxyalkoxylation of epoxidized methyl oleate by an amphiphilic ionic liquid catalyst

AbstractOleic acid is an attractive biobased platform chemical. Precursors for biobased materials can be accessed by epoxidation and subsequent hydroxyalkoxylation of oleic acid. The hydroxyalkoxylation step is conventionally performed with sulfuric acid or a metal catalyst. Due to their high polarity, many ionic liquid catalysts are ineffective for hydroxyalkoxylation of fatty acid derivatives with non‐polar alcohols. In this work, we utilized an amphiphilic ionic liquid catalyst to perform hydroxyalkoxylations of epoxidized methyl oleate. An ionic liquid catalyst based on dimethyl lauryl amine was synthesized and evaluated for this reaction due to its long alkyl group. The amphiphilic nature of the ionic liquid allowed for better miscibility and reactivity compared to other ionic liquids. Several alcohols were used with high yields (≥80%) and selectivity (≥92%), including nonpolar alcohols with longer alkyl chains such as octanol and dodecanol. The high selectivity of these conditions could be advantageous for applications in lubricants, biofuels, or polyol preparation. This work demonstrates a greener alternative to conventional hydroxyalkoxylation catalysts.

Amphiphilic Ionic Liquids Capable to Formulate Organized Systems in an Aqueous Solution, Designed by a Combination of Traditional Surfactants and Commercial Drugs.

The present review describes the state of the art in the conversion of pharmaceutically active ingredients (API) in amphiphilic Ionic Liquids (ILs) as alternative drug delivery systems. In particular, we focus our attention on the compounds generated by ionic exchange and without original counterions which generate different systems in comparison with the simple mixtures. In water, these new amphiphiles show similar or even better properties as surfactants in comparison with their precursors. Cations such as 1-alkyl-3-methyl-imidazolium and anions such as dioctyl sulfosuccinate or sodium dodecyl sulfate appear as the amphiphilic components most studied. In conclusion, this work shows interesting information on several promissory compounds and they appear as an interesting challenge to extend the application of ILs in the medical field.

Effect of amphiphilic ionic liquids on the colorimetric properties of polyketides colorants

Consumers are currently pressuring the food industries to replace synthetic colorants with their natural counterparts. However, natural colorants still represent less than a third of food coloring additives, as they are more difficult to produce and present application issues due to their lower stability. To find surfactants compatible with natural colorants, this study evaluated the effect of amphiphilic ionic liquids (ILs) aqueous solutions on the colorimetric properties of polyketides colorants (yellow-orange and red color) produced by Talaromyces amestolkiae. Only the IL n-alkyl-3-methylimidazolium bromide ([Cnmim]Br with n = 10) at 2.5 mM preserved the colorimetric and fluorescence characteristics of the fungal colorants, while the other surfactants [e.g., [Cnmim]Br with n = 12, 14, and 16, tributyl-tetradecylphosphonium chloride ([P4,4,4,14]Cl), and cetyltrimethylammonium bromide (CTAB)] altered them. Fluorescence was more sensitive to the effect of ILs than their color and absorbance. Furthermore, the red colorant was more affected by the ILs than the yellow-orange chromophores. Hence, this work shows that formulations with [C10mim]Br (up to 2.5 mM) can preserve the properties of T. amestolkiae polyketides colorants, while the other ILs can be used as additives to modulate their color and fluorescence for biosensing applications.

New Amphiphilic Ionic Liquids for the Demulsification of Water-in-Heavy Crude Oil Emulsion.

This work aimed to use abietic acid (AA), as a widely available natural product, as a precursor for the synthesis of two new amphiphilic ionic liquids (AILs) and apply them as effective demulsifiers for water-in-crude oil (W/O) emulsions. AA was esterified using tetraethylene glycol (TEG) in the presence of p-toluene sulfonic acid (PTSA) as a catalyst obtaining the corresponding ester (AATG). AATG was reacted with 1-vinylimidazole (VIM) throughout the Diels–Alder reaction, forming the corresponding adduct (ATI). Following this, ATI was quaternized using alkyl iodides, ethyl iodide (EI), and hexyl iodide (HI) to obtain the corresponding AILs, ATEI-IL, and ATHI-IL, respectively. The chemical structure, surface activity, thermal stability, and relative solubility number (RSN) were investigated using different techniques. The efficiency of ATEI-IL and ATHI-IL to demulsify W/O emulsions in different crude oil: brine volumetric ratios were evaluated. ATEI-IL and ATHI-IL achieved promising results as demulsifiers. Their demulsification efficiency increased as the brine ratios decreased where their efficiency reached 100% at the crude oil: brine ratio (90:10), even at low concentrations.

Micellization and aggregation approach in aqueous amphiphilic ionic liquid and anionic polymer system

In this study, we investigate the aggregation of an ionic liquid (IL), 1-allyl-3-methylimidazolium bromide ([AMIM][Br]) in aqueous solution containing variable amounts of poly(diallyldimethylammonium) chloride (PDADMAc), using conductivity, density, and viscosity techniques in combination with the molecular dynamics simulation approach. The critical micelle concentration (cmc) after micellization for IL in solutions was derived from the conductivity measurements. The effect of PDADMAc on the physicochemical properties of IL in aqueous solution was investigated using comprehensive biophysical techniques such as UV-visible absorption spectroscopy, viscosity (η) and density (ρ) measurements. With the addition of PDADMAc concentration (0, 0.25, 0.05, and 0.1 g.l-1), cmc values increased due to the interaction between IL and PDADMAc. Our UV spectroscopy results showed that the interaction between PDADMAc and [AMIM][Br] was due to the significant differences in the interactions between the amide group of the polymer, the ionic liquid ions, and the water molecules. The apparent molar volumes (V) were calculated from the experimental densities for the (AMIM)(Br)-PDADMAc systems studied. Viscosity data decreased with increasing IL concentration and increased with [PDADMAc]. A computer simulation was used to investigate the aggregate structure between (AMIM)(Br]) and PDADMAc.

Regulation of anionic structure and CO2 on the vesicle formation of imidazolium-based ionic liquids in water

The understanding of vesicle formation mechanism of ionic liquids (ILs) in aqueous solution is of great significance for the innovation and application of IL vesicles. In this work, a series of single-tailed amphiphilic ionic liquids (ILs) consisted of 1-tetradecyl-3-methylimidazolium [C14mim]+ and five kinds of anions have been designed to examine the regulation of anionic structures on the vesicle formation of ILs in water without any additives by surface tension, conductivity, cryogenic transmission electron microscopy, dynamic light scattering, small-angle X-ray scattering, and NMR spectroscopy. It is found that synergistic effect of hydrophobic and π-π interaction plays a vital role in the vesicle formation of 1-tetradecyl-3-methylimidazolium 1, 2, 3-benztriazole ([C14mim][1, 2, 3-Ben]). Interestingly, reversible structural transition between vesicle and micelle of this IL is observed by alternating CO2 and N2 bubbling due to the reversible formation of carbamate arising from the reaction between CO2 and the anion of the IL.

Review on Amphiphilic Ionic Liquids as New Surfactants: From Fundamentals to Applications.

The demand for lowering interfacial tension (IFT) in different processes has persuaded researchers to use stable and resistant surfactants with low environmental impact. For this purpose, surface-active ionic liquids (SAILs) have attracted much attention owing to their good amphiphilic nature and prominent properties like recyclability and high performance under harsh conditions. This review initially explains how the IFT and critical micelle concentration of different systems vary in the presence of different SAILs with a variety of alkyl chain lengths, head groups, and counter anions. Towards this aim, some physicochemical properties of SAILs as well as the corresponding theoretical aspects of adsorption are considered. Then, recent advances in utilizing SAILs for reducing IFT of different chemical systems are surveyed. Relevantly, the role of important operating parameters of temperature, pH, presence of electrolytes, and the chemical nature of involved phases are adequately discussed. Further, an overview of different SAILs applications in stabilization, separation, and in petroleum industries is scrutinized. To allow better judgment, precise comparisons between different types of SAILs and conventional surfactants are provided. Finally, challenges and possible directions of future research on SAILs are highlighted.