Crystal Phase Ionic Liquids for Energy Applications: Heat Capacity Prediction via a Hybrid Group Contribution Approach

In the selection and design of ionic liquids (ILs) for various applications, including heat transfer fluids, thermal energy storage materials, fuel cells, and solvents for chemical processes, heat capacity is a key thermodynamic property. While several attempts have been made to develop predictive models for the estimation of the heat capacity of ILs in their liquid phase, none so far have been reported for the ILs' solid crystal phase. This is particularly important for applications where ILs will be used for thermal energy storage in the solid phase. For the first time, a model has been developed and used for the prediction of crystal phase heat capacity based on extending and modifying a previously developed hybrid group contribution model (GCM) for liquid phase heat capacity. A comprehensive database of over 5000 data points with 71 unique crystal phase ILs, comprising 42 different cations and 23 different anions, was used for parameterization and testing. This hybrid model takes into account the effect of the anion core, cation core, and subgroups within cations and anions, in addition to the derived indirect parameters that reflect the effects of branching and distribution around the core of the IL. According to the results, the developed GCM can reliably predict the crystal phase heat capacity with a mean absolute percentage error of 6.78%. This study aims to fill this current gap in the literature and to enable the design of ILs for thermal energy storage and other solid phase applications.

Surfing the Third Wave of Ionic Liquids: A Brief Review on the Role of Surface-Active Ionic Liquids in Drug Development and Delivery

The relevance of ionic liquids (ILs) is now well established in many fields, as their unique properties make them appealing as 1) greener alternatives to organic solvents (first-generation ILs), 2) tunable task-specific materials (second-generation ILs), and 3) multifunctional players in life and pharmaceutical sciences (third-generation ILs). This third wave of ILs encompasses a wide range of compounds, from bioactive molecules with single or even dual therapeutic action, to potential ingredient molecules for drug formulation and transport systems. In this context, the focus of this review is the emergent role of surface-active ionic liquids (SAILs) in drug development and delivery.

Scrutinizing Self-Assembly, Surface Activity and Aggregation Behavior of Mixtures of Imidazolium Based Ionic Liquids and Surfactants: A Comprehensive Review

The desire of improving various processes like enhanced oil recovery (EOR), water treatment technologies, biomass extraction, organic synthesis, carbon capture etc. in which conventional surfactants have been traditionally utilized; prompted various researchers to explore the self-assembly and aggregation behavior of different kinds of surface-active molecules. Ionic liquids (ILs) with long alkyl chain present in their structure constitute the advantageous properties of surfactant and ILs, hence termed as surface-active ionic liquids (SAILs). The addition of ILs and SAILs significantly influence the surface-activity and aggregation behavior of industrially useful conventional surfactants. After a brief review of ILs, SAILs and surfactants, the prime focus is made on analyzing the self-assembly of SAILs and the mixed micellization behavior of conventional surfactants with different ILs.

Micellization Behavior of Conventional Cationic Surfactants within Glycerol-Based Deep Eutectic Solvent

The aggregation behavior of two cationic surfactants, i.e., cetyldimethylethanolammonium bromide (CDMEAB) and cetyltributylphosphonium bromide (CTBPB), within an aqueous deep eutectic solvent (DES) is studied. The synthesized DES is composed of 1:2 mole ratio of choline chloride and glycerol and is further characterized by Fourier transform infrared (FTIR) and 1H NMR spectroscopy techniques. The critical micellar concentration (CMC), micellar size, and intermolecular interaction in surfactants within Gly-based DES solutions are investigated by various techniques including surface tension, conductivity, fluorescence, dynamic light scattering (DLS), FTIR, 1H NMR, and two-dimensional (2D) nuclear Overhauser effect spectroscopy (NOESY). The various interfacial properties and thermodynamic parameters are determined in the presence of 5 wt % glyceline (Gly)-based DES in an aqueous solution. The CMC, aggregation number (N agg), and Stern-Volmer constant (K sv) have also been determined by a steady-state fluorescence method. DLS is used to obtain information regarding the size of the aggregates formed by the cationic surfactants in DES solutions. FTIR spectroscopy is used to study the surfactant-DES interactions that tune the micellar structure of the surfactants within the Gly-based DES solution. The functional groups involved in the interactions (H-bonding and electrostatic) are the head groups (HO-CH2-CH2-N+ ion for CDMEAB and quaternary phosphonium (P+) ion for CTBPB) of the surfactants with the -OH-containing Gly DES. The hydrophobic moieties are involved in the hydrophobic interactions. The 1H NMR data show that differences in chemical shifts can provide significant information about the interactions taking place within the system. 1H NMR and NOESY techniques are further employed to strengthen our claim on the feasible structural arrangements within the aqueous surfactant-DES self-assembled structures. It is observed that both the cationic surfactants, i.e., CDMEAB and CTBPB, form self-assembled nanostructures in the Gly-based DES solutions. The present results are expected to be useful for colloidal solutions of DES and their mixtures with water.

High-Performance Green Light-Emitting Diodes Based on MAPbBr3 with π-Conjugated Ligand

The morphology, crystal size, and trap density of perovskite films significantly affect the luminescent properties of perovskite light-emitting diodes (PeLEDs). Recently, numerous studies have been conducted on ligands that surround the surface of perovskite crystals and passivate the trap sites to improve the performance of PeLEDs. In this study, a 4-aminobenzonitrile (ABN) ligand improved the performance of methylammonium lead bromide (MAPbBr₃)-based PeLEDs by reducing the MAPbBr₃ crystal size to the nanoscale and reducing the trap density. Moreover, the properties of PeLEDs with ABN were further improved using a surface-modified hole-transport layer (HTL) with a hydrophilic polymer. Finally, a bright green PeLED was fabricated, which exhibited the maximum luminance of 3350 cd/m² with an external quantum efficiency of 8.85%. Therefore, it is believed that the use of proper ligands for the perovskite layer and the optimization of the charge-transport layer have great potential for the development of high-performance PeLEDs.

Novel Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity as Both Solvents and Catalysts for Friedel–Crafts Alkylation

Unique tunable aryl-imidazolium magnetic ionic liquids with dual functions as a solvent–catalyst and dual Brønsted–Lewis acidity (B-L MILs) are applied for Friedel–Crafts alkylation without additional solvents. The catalytic properties of these B-L MILs in the Friedel–Crafts alkylation of p-xylene with benzyl chloride are investigated. The various reaction parameters, including the catalyst dosage, reaction time, reaction temperature, molar ratio of reactants, and reusability, are discussed. The results show that the B-L MIL 5c has more excellent product selectivity (>99%) and reactant conversion (>99%) under the following optimum conditions (reaction temperature = 80 °C, reaction time = 0.5 h, molar ratio of p-xylene to benzyl chloride = 6:1, and catalyst 5c dosage = 1.0 mole %) than traditional catalysts reported in the previous literature. Specifically, due to the mesomeric effect between the FeCl4 anion and hydrogen atom at cationic moiety, the catalyst B-L MILs with the molar fraction of FeCl3 equal to 0.5 can be easily recovered and provide satisfactory catalytic activity after being re-used six times.

Synthesis and Properties of Magnetic Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity

A series of unique tunable aryl-imidazolium magnetic ionic liquids (MILs) with dual acidity that contain both Brønsted and Lewis acidic sites (abbreviated as B-L MILs) were synthesized and characterized using nuclear magnetic resonance and mass spectrometry. Physical properties, such as thermal properties, magnetic susceptibility, and Brønsted and Lewis acidity, were measured. These properties were found to depend on the cation structure. These B-L MILs had good solubility in many organic solvents, good thermal stability, and low melting points, and exhibited magnet-like behavior. For these B-L MILs, the Brønsted acidity was measured using ultraviolet-visible (UV-Vis), and the Lewis acidity was measured using Fourier transform infrared spectroscopy (FTIR). The results showed that B-L MILs with an electron-withdrawing group in the aryl-imidazolium moiety had higher Brønsted acidity, whereas those with an electron-donating group had higher Lewis acidity. This type of ionic liquid, with both Brønsted and Lewis acidic sites, is expected to be a useful solvent and catalyst for organic reactions.

A detailed structural study of cytotoxicity effect of ionic liquids on the leukemia rat cell line IPC-81 by three dimensional quantitative structure toxicity relationship

In the present study, a very thorough and in-depth three-dimensional quantitative structure-toxicity relationship (3D-QSTR) analysis has been implemented to make a correlation between the structural information of the ionic liquids (ILs) and their cytotoxicity towards Leukemia rat cell line IPC-81, as one of the ILs' toxicological consequences. To do this, alignment free GRid-INdependent Descriptors (GRINDs), which were derived from molecular interaction fields (MIFs), were correlated to the cytotoxicity values by partial least squares (PLS) and support vector regression (SVR). Genetic algorithm (GA), as a powerful linear tool, was used to select the best and interpretative subset of variables for the predictive model building. The selected variables with the capability to screen the effective structural features, showed direct and inverse contribution to the cytotoxicity. In silico modeling can reduce the amount of cellular testing necessary by predicting the toxicological functions of the chemical structures. Acceptable predictions of both internal and external validation sets made it possible to develop the predictive models for a large set of 269 diverse ILs containing 9 cationic cores and 44 types of anions. The constructed 3D-QSTR models use simple and interpretable descriptors to provide an in-depth and mechanistic interpretation of structural characteristics. This helps provide a clear understanding of the cytotoxicity effects of the understudy ILs. The effects of the nature of the cations, anions, and substituents on the cytotoxicities were evaluated and discussed.

Ionic liquid mediated micelle to vesicle transition of a cationic gemini surfactant: a spectroscopic investigation

In this contribution, we have examined a composition dependent self aggregated structural modification of a catanionic mixture of the surface active ionic liquid (IL) 1-butyl-3-methylimidazolium octyl sulphate and a cationic gemini surfactant (14-5-14) in aqueous medium. We have observed that the hydrodynamic diameter of the aggregates increases with increasing IL concentration and microscopic evidence (HRTEM, FESEM, and LCSM) shows the formation of vesicle like aggregates (Dh ≈ 200 nm) at XIL = 0.5. The steady state fluorescence anisotropy of the membrane binding probe DPH shows a micelle to vesicle transition at this composition. The viscosity of the solution shows a peak at XIL = 0.3, indicating the formation of a worm like micelle as an intermediate of the micelle to vesicle transition. The rotational dynamics shows a stiffer surfactant packing in the vesicles compared to the micelles, whereas, the solvation dynamics measurements indicate a higher abundance of bound type water in the vascular medium compared to that for the micelle. The formed vesicles also show stability towards temperature and biomolecules, which can be used for respective applications.

Interplay of Noncovalent Interactions in Ionic Liquid/Sodium Bis(2-ethylhexyl) Sulfosuccinate Mixtures: From Lamellar to Bicontinuous Cubic Liquid Crystalline Phase

Phase transitions in mixtures of imidazolium based ionic liquid ([C₁₂mim]Br) and anionic double tail surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT), were studied using a multitechnique approach. The system was primarily chosen for its expected ability to form a variety of lamellar and nonlamellar liquid crystalline phases which can transform into each other via different mechanisms. Depending on the bulk composition and total surfactant concentration, mixed micelles, coacervates, and lamellar and inverse bicontinuous cubic liquid crystalline phase were observed. Along with electrostatic attractions and geometric packing constraints, additional noncovalent interactions (hydrogen bonding, π-π stacking) enhanced attractive interactions and stabilized low curvature aggregates. At stoichiometric conditions, coexistence of coacervates and vesicles was found at lower, while bicontinuous cubic phase and vesicles were present at higher total surfactant concentrations. The phase transitions from a dispersed lamellar to inverse cubic bicontinuous phase occur as a consequence of charge shielding and closer packing of oppositely charged headgroups followed by a change in bilayer curvature. Transition is continuous with both phases coexisting over a relatively broad range of concentrations and very likely involves a sponge-like phase as a structural intermediate. To the best of our knowledge, this type of phase transition has not been observed before in surface active ionic liquid/surfactant mixtures.

Ionic liquids as modulators of physicochemical properties and nanostructures of sodium dodecyl sulfate in aqueous solutions and potential application in pesticide microemulsions

The change of morphology of ILs/SDS aggregates with increased concentration of ILs.

Aggregation of 1-alkyl-3-methylimidazolium octylsulphate ionic liquids and their interaction with Triton X-100 micelles

Halogen-free surface active and biamphiphilic ionic liquids 1-alkyl-3-methylimidazolium octylsulphates (Cnmim C₈SO₄, n = 4, 6, 8, 10) were synthesized and their aqueous solution behaviour was studied using NMR and scattering techniques.

Complexation of triblock reverse copolymer 10R5 with surface active ionic liquids in aqueous medium: a physico-chemical study

A comprehensive study on the interactions of surface active ionic liquids (SAILs) [C_nmim][Cl], where n = 8, 10, and 12, with a triblock reverse copolymer, 10R5, [(PPO)₈–(PEO)₂₂–(PPO)₈] has been performed using various physico-chemical techniques.

Synthesis and characterization of a helicene-based imidazolium salt and its application in organic molecular electronics

Herein we demonstrate the synthesis of a helicene-based imidazolium salt. The salt was prepared by starting from racemic 2-methyl[6]helicene, which undergoes radical bromination to yield 2-(bromomethyl)[6]helicene. Subsequent treatment with 1-butylimidazole leads to the corresponding salt 1-butyl-3-(2-methyl[6]helicenyl)-imidazolium bromide. The prepared salt was subsequently characterized by using NMR spectroscopy and X-ray analysis, various optical spectrometric techniques, and computational chemistry tools. Finally, the imidazolium salt was immobilized onto a SiO2 substrate as a crystalline or amorphous deposit. The deposited layers were used for the development of organic molecular semiconductor devices and the construction of a fully reversible humidity sensor.

The effects of counterion composition on the rheological and conductive properties of mono- and diphosphonium ionic liquids

A series of monocationic and dicationic phosphonium ionic liquids was prepared and their thermal, rheological, and conductive properties were characterized. These phosphonium ionic liquids were paired with seven monoanionic counterions (chloride, hexafluorophosphate, hexafluoroantimonate, octanoate, perfluorooctanoate, dodecyl sulfate, dioctyl sulfosuccinate, and bis(trifluoromethane)sulfonimide) in order to examine the effects of the counterion size and chemical structure on bulk properties of the phosphonium ionic liquids. The length of the three alkyl chains surrounding the phosphorus atom was also varied from butyl, hexyl to octyl on the cation. All of the samples exhibited initial decomposition temperatures above 150 °C. The octanoate and its fluorinated analog possessed the lowest decomposition temperature and the dicationic hexyl sample bis(trifluoromethane)sulfonimide possessed the highest (>370 °C). The dicationic butyl and hexyl chloride samples displayed similar G', G″ and viscosity curves, whereas the dicationic octyl chloride sample exhibited significantly lower values. The frequency sweeps of the monocationic phosphonium ionic liquids were all similar and showed minimal side chain dependence. The monocationic phosphonium ionic liquids have higher conductivity than their dicationic analogs at all measured temperatures.

Imidazolium-based ionic liquids grafted on solid surfaces

Supported ionic liquids (SILs), which refer to ionic liquids (ILs) immobilized on supports, are among the most important derivatives of ILs.