Ionic Liquid Mixtures Research Articles

Second law of thermodynamics, heat transfer, and pumping power analyses of water and ionic liquid mixture based MXene nanofluids in a shell and helical coil heat exchanger

Heat exchangers are extensively employed across diverse sectors for efficient thermal (heat)transfer between two fluids, specifically from a hot fluid to a cold fluid. Nanofluids are promising heat transfer fluids that exhibit exceptional thermal performance in heat exchangers. The present study examines the thermodynamic second law efficiency analysis of a shell and helical coil heat exchanger utilizing MXene/80:20% water+[MMIM][DMP] (mass percentage) based ionanofluids. An analytical investigation was conducted on the heat transfer coefficient, entropy generation rate, and exergy efficiency of a shell and helical coil heat exchanger, considering particle weight loadings from 0.2% to 1.0%, Reynolds numbers from 500 to 4300, and flow rates from 0.5 to 3.5 L/min. In the base fluid, at 1.0 wt.% and at a Reynolds number of 3598, the increase in heat transfer, Nusselt number, friction factor, pressure drop, effectiveness, and frictional entropy generation are 45.59%, 28.27%, 15.19%, 12.56%, 17.20%, and 16.21%, respectively. Concurrently, thermal entropy generation, and total exergy destruction were reduced by 46.23% and 20.08%, respectively. The second law (exergy) efficiency and thermal performance factor are improved by 34.04% and 1.384-times, respectively, at 1.0 wt.% and at a Reynolds number of 3598, compared to the base fluid. The data from the current study is corroborated by existing literature. New correlations were developed from the computed data points to estimate the Nusselt number and friction factor.

Effects of Ionic Liquids on the Nucleofugality of Dimethyl Sulfide.

The nucleofugality of dimethyl sulfide was measured in solvent mixtures containing ionic liquids. The first-order rate constants of the solvolysis of sulfonium salts were determined in mixtures containing different proportions of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide in ethanol, representing the first report on the solvolysis of a charged species in an ionic liquid. Temperature-dependent kinetic studies allowed determination of activation parameters and rationalization of observed solvent effects in different ionic liquid mixtures. From the solvolysis data, the nucleofugality of dimethyl sulfide in different proportions of this ionic liquid in ethanol was determined. Further, the nucleofugality of dimethyl sulfide was determined in mixtures containing high proportions of each of seven other ionic liquids in ethanol. These data allowed quantification of the effects of varying both the amount of ionic liquid present and on changing the components of the ionic liquid on the nucleofugality of dimethyl sulfide. The ionic liquid mixtures were shown to affect the nucleofugality of this nucleofuge in a different manner to the previously studied monatomic charged nucleofuges, owing to different microscopic interactions in solution. This work highlighted the necessity of considering electrofuges with an appropriate range of electrofugality values along with the importance of the nucleofuge-specific sensitivity parameter.

A novel trialkyl phosphate – Ionic liquid mixture for an efficient separation of Lithium ion from its acidic feed solution

Separation of Lithium ion (Li+) using conventional non-crown type ligands through solvent extraction process is a challenging task and can only be feasible by tuning the organic phase with an additional polar environment. In this context, we have projected an extracting system containing a traditional trialkyl phosphate (T(alk)P): Tri-iso-amyl phosphate (TiAP) containing a minimal amount of ionic liquid (IL): [C4mpip][NTf2] (1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide) for the efficient extraction and separation of Li+ from its hydrochloric acid feed. The extraction performances pertaining various experimental parameters were realized to explore the solvent potentiality of TiAP/[C4mpip][NTf2] towards Li+ coordination. Involvement of two ligand molecules in extraction in presence of 10 % (v/v) IL diluent offers fast extraction kinetics and turns the extraction mechanism into a cation exchange pathway, which was further examined by using different classes of ILs in conjunction with TiAP for Li+ uptake. The selectivity of Li+ over other alkali (or alkaline earth) metal ions was investigated to highlight the affinity of the proposed IL system towards Li+. Extraction scenario in TiAP phase was compared with that in TBP phase containing same IL to bring out the efficacy of the proposed IL system. The stripping performance of Li+ from the loaded organic phase was studied using an acid solution to establish the sustainability of the proposed extraction process.

Efficient synthesis of cellulose acetate through one-step homogeneous acetylation of cotton cellulose in binary ionic liquids

Cellulose acetate (CA) is an important cellulose derivative with a wide range of applications. To adopt a more efficient and environmentally friendly method to synthesize cellulose acetate, a binary ionic liquid mixture of 1-butyl-3-methylimidazole chloride salt (BmimCl) and 1-butyl-3-methyldihydroimidazole phosphate (BmimH2PO4) was used. Compared to the conventional methods, this approach didn't require pre-activation of cellulose and the process of homogeneous acetylation proceeded without a catalyst. By simply adjusting the reaction conditions, cellulose acetate with a degree of substitution (DS) in the range of 0.83–3.0 was produced by one-step homogeneous acetylation without hydrolysis. Furthermore, the cellulose acetate film produced by solvent casting exhibited smooth surface characteristics, 95 % transparency, and 57.9 MPa tensile strength. Therefore, this study highlights the importance of using binary ionic liquid mixtures for facile synthesis of cellulose acetate. Due to their excellent transparency and mechanical properties, newly synthesized cellulose acetate films could replace commercial films.

Binary imidazolium based aqueous ionic liquid droplet on a rough surface: a molecular dynamics study

Ionic liquids (ILs) have garnered immense attention due to their tunable physicochemical properties. In this study, we delve into the wetting behaviour and interfacial properties of aqueous binary IL mixtures containing [EMIM] [BF4] and [HMIM] [BF4] on both smooth and rough graphite surfaces. Employing classical molecular dynamics simulations, we systematically explored the effects of IL concentration and surface morphology on wetting phenomena. To ensure the equilibrium of the systems, we began by calculating the interaction energies between the components. Subsequently, contact angles were computed, shedding light on the wetting characteristics of the aqueous binary IL mixtures. We meticulously examined the density profiles of the IL systems from the substrate to unravel the dominance of one IL over the other, exploiting the hydrophilic nature of [EMIM] [BF4] and the hydrophobic nature of [HMIM] [BF4]. A comprehensive analysis of hydrogen bond distribution allowed us to discern the intricate nature of these aqueous binary IL droplets. We probed the changes in intermolecular forces within the aqueous IL solution by investigating surface tensions. The tunability of these ILs emerges as a significant aspect of our study, paving the way for their tailored application in engineering and scientific domains. Schematic diagram showing the density distribution of hydrophilic and hydrophobic ILs ([EMIM] [BF4] and [HMIM] [BF4]) in water and also the hydrogen bond (HB) distribution of anion ([BF4]−) water inside the droplet on a pillared surface with a surface fraction ( f ) of 0.4 and pillar height of H = 4 .

Molecular Insights of 5-Hydroxymethylfurfural in a Mixture of Ionic Liquids and Alkylated Phenolic Solvents.

This paper presents all-atom molecular dynamics to understand the separation behavior of 5-hydroxymethylfurfural (5-HMF) from 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]+[BF4]- using alkylated phenols as extractants. We have utilized four solvents such as 4-methyl phenol (4-MP), 4-ethyl phenol (4-EP), 4-propyl phenol (4-PP), and 4-butyl phenol (4-BP). We perform structural, dynamic, and rigorous thermodynamic analyses of 5-HMF in the mixture of ILs and solvents. The [BMIM]+[BF4]- show a strong interaction with phenols. The self-diffusion coefficient of 5-HMF shows a 3-fold increase with a decrease in the methyl group on the phenol. The solvation-free energy (ΔGsolvation) of 5-HMF shows favorably in phenols. On the other hand, the transfer free energy (ΔGtransfer) of 5-HMF presents favorable from ILs to phenols. The partition coefficient (log P) values show favorability for separation of 5-HMF using phenols. Overall, the molecular level analysis provides the role of the alkyl group effect on the phenols for extracting 5-HMF from the ILs.

Synthesis and characterization of TiO2/ZnO/SiO2 nanocomposite using pyrrolidinium-based ionic liquids via sol–gel-hydrothermal method for photocatalytic removal of Pb (II) ions

This study aims to synthesize TiO2 with precise particle morphology, a large surface area, a stable anatase phase at high temperatures, and enhanced catalytic activity in the visible light spectrum. TiO2 was combined with ZnO and SiO2 to form a TiO2/ZnO/SiO2 composite (TZS). A TiO2/ZnO/SiO2 composite (TZS) was synthesized via sol–gel-hydrothermal method at 180 °C for 24 h employing a water-pyrrolidinium-based ionic liquid mixture. XRD analysis confirmed anatase, zincite, and amorphous silica phases post-calcination at 450 °C. Compared to water alone, TZS synthesized with the water-ILs media exhibited higher surface area and narrower band gap energy. TG-DTA analysis confirmed anatase phase stability up to 1000 °C. SEM and TEM images showed TZS particles synthesized using water as spherical, while the water-ILs mixture produced nanocoral, nanorod, and nanocubic morphologies. In photocatalysis, TZS synthesized with water-ILs removed Pb(II) ions by 99.98 %, surpassing water-synthesized TZS at 95.49 % indicating superior photocatalytic of TZS synthesized with water-ILs.

Size polydisperse model ionic liquid under confinement: A molecular dynamics study

The performance of an electric double-layer capacitor is strongly influenced by the choice of electrolyte, and the use of ionic liquid (IL) mixtures as an electrolyte has shown great promise. In this study, a model IL made of a mixture of anions and size-polydisperse cations in equal numbers and confined between two electrodes is investigated by means of molecular dynamics simulations. In particular, using the extent of size-polydispersity (characterized by polydispersity index, δ) as a control parameter, we systematically explore its effect on the local structure, charge profile, ion size distribution in the vicinity of electrode surfaces, and differential capacitance. It is observed that the charge density profiles near cathode, i.e., region comprising both Stern and diffused layers, are significantly affected under the variation of δ in addition to the electrode charge density. Ion population, ordering of different-size cations, and its effective size in the vicinity of electrodes under neutral and applied potential conditions are also quantified. An interesting observation is that the effective cation size in the Stern layer decreases with increasing value of δ in the case of moderate to strong electrode surface charge density. This behaviour can be qualitatively understood from the interplay of enthalpic and entropic forces in the system. Finally, a non-monotomic dependence of capacitance on δ is observed with maximum value of capacitance at a rather small value of δ(≈3%) for the model system.

Insight into behaviors of internal interactions and thermodynamic properties of binary mixtures composed of ether-functionalized ionic liquids and 1,4-butyrolactone or propylene carbonate

A deeper comprehension of the mechanism behind various internal interactions and their influence on system properties encourages the utilization of ionic liquid mixture systems. In this work, the excess molar volume, viscosity deviation, change of electrical conductivity, and ionicity of both binary mixtures for N-methyl-N-methoxyethylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([MOEMPYrr][TFSI]) ether-functionalized ionic liquids (ILs) with 1,4-butyrolactone (GBL) or propylene carbonate (PC) were systematically studied. The specific interactions between ILs and solvent molecules were investigated by using the COSMO-RS model in terms of DFT calculation. The results indicate that [MOEMPYrr]+ tends to act as a hydrogen bond donor and [TFSI]- tends to act as a hydrogen bond acceptor, and GBL (or PC) has a strong hydrogen bond acceptance ability. Furthermore, based on the radial distribution functions (RDFs) from molecular dynamics (MD) simulations, the H1 atom in [MOEMPYrr]+, the O2 atom in [TFSI]-, the O3 atom in GBL, and the O4 atom in PC are selected as reference sites to study the interaction between cations and anions (or solvent molecules). It is found that the interaction between anions and cations in the [MOEMPYrr][TFSI] + PC system is stronger than that in the [MOEMPYrr][TFSI] + GBL system, and the interaction between cations and GBL is stronger than that between cations and PC. This result further explains why the excess molar volumes (VE) of [MOMPYrr][TFSI] + GBL binary mixtures are greater than that of [MOMPYrr][TFSI] + PC binary mixtures from a microscopic perspective.

Design and Characterization of Epoxy Resin Systems Based on Mixtures of Imidazolium-Based Ionic Liquids with Docusate and Dicyanamide Anions

This study focuses on the synthesis, characterization, and application of four ionic liquids (ILs), three of which are being reported for the first time, with unique thermal properties and diverse anion-cation combinations, specifically in the context of epoxy resin polymerization. 1-3-Didodecylimidazolium dicyanamide (dDDIM DCA), 1-3-Didodecylimidazolium docusate (dDDIM DOSS), 1-ethyl-3-methylimidazolium dicyanamide (EMIM DCA), and 1-ethyl-3-methylimidazolium docusate (EMIM DOSS) were used to prepare six different mixtures with the same cation and with varying concentrations of DCA components, which is the main factor of an efficient polymerization, while the other component is intended to modify the properties of the cured resin. Mixtures based on EMIM cation demonstrated increased enthalpy and lower onset polymerization temperatures, indicating more efficient curing processes. The hardness of cured epoxy resins can be adjusted by altering the curing temperature and IL composition, with EMIM DCA and EMIM DOSS mixtures displaying high Shore A hardness, suitable for durable surface applications. In contrast, mixtures with higher dDDIM DCA proportions offered a balance between rigidity and flexibility, ideal for applications requiring both mechanical strength and elasticity.

Physicochemical and catalytic behavior of binary mixtures of n-alkyl imidazolium bromide ionic liquids with poly (ethylene glycol)-400: Application of flory statistical theory

In this work, Flory statistical theory is employed to predict the important physicochemical properties namely density, isothermal compressibility, internal pressure, coefficient of volume expansion, energy of vaporization, heat of vaporization, cohesive energy density, solubility parameter and polarity index for three binary mixtures of PEG-400 + [CnMim][Br], where n=4, 6, and 8 at different temperatures (T= 298.15 K, 308.15 K, and 318.15 K). Furthermore, the applicability of Flory statistical theory to predict certain physicochemical properties has been verified. Excess properties viz., excess enthalpy, excess Gibbs free energy, and excess entropy are also determined for these binary mixtures. The variation of energy of vaporization, heat of vaporization, solubility parameter and excess parameters are used to analyze the catalytic behavior and prevalent molecular interactions of these mixtures.

Comparison between Phosphonium Docusate Ionic Liquids and Their Equimolar Mixtures with Alkanes: Temperature-Dependent Viscosity, Glass Transition, and Fragility.

In this study, we determined the temperature-dependent viscosities, glass transition temperatures, and fragilities of tetraalkylphosphonium docusate ionic liquids (ILs) and their equimolar mixtures with alkanes to elucidate the effects of the alkyl groups on the phosphonium cation. The target ILs were the docusate salts with tributylheptylphosphonium ([P4447][doc]), tributyltetradecylphosphonium ([P444,14][doc]), butyltrihexylphosphonium ([P4666][doc]), trihexylheptylphosphonium ([P6667][doc]), and trihexyltetradecylphosphonium cations ([P666,14][doc]). The comparable IL/alkane mixtures were equimolar mixtures of IL and alkane with the same carbon numbers of the target ILs: [P4447][doc]/hexane to [P6667][doc]; [P4447][doc]/heptane to [P444,14][doc]; [P444,14][doc]/hexane to [P666,14][doc]; [P4666][doc]/decane to [P666,14][doc]; and [P6667][doc]/heptane to [P666,14][doc]. The viscosities and glass transition temperatures of the neat ILs were higher than those of their respective IL/alkane mixtures. Based on the analysis of temperature-dependent viscosities, including a viscosity value of 1013 mPa·s at the glass transition temperature using the Vogel-Fulcher-Tammann equation, the neat ILs were stronger liquids than the corresponding IL/alkane mixtures. By comparing several combinations of the neat ILs and IL/alkane mixtures, we found that the larger the alkane, the more fragile the mixture.

Reversible phase transition poly(benzyl methacrylate)/ionic liquid electrolytes for effective overheating protection in lithium batteries

Battery safety is influenced by various factors, with thermal runaway being one of the most significant concerns. While most studies have concentrated on developing one-time, self-activating mechanism for thermal protection, such as temperature-responsive electrodes, and thermal-shutdown separators, these methods only provide irreversible protection. Recently, reversible temperature-sensitive electrolytes have emerged as promising alternatives, offering both thermo-reversibility and self-protective properties. However, further research is crucial to fully understand these thermal-shutdown electrolytes. In this study, we propose lower critical solution temperature (LCST) phase behavior poly(benzyl methacrylate)/imidazolium-based ionic liquid mixtures to prepare temperature-sensitive electrolytes that provide reversible thermal shutdown protection of batteries. This electrolyte features an appropriate protection temperature (∼105°C) and responds quickly within a 1 min at 105°C, causing cells to hardly discharge as the voltage suddenly drops to 3.38 V, and providing efficient thermal shutdown protection within 30 min. Upon cooling back to room temperature, the battery regains its original performance. Additionally, the electrolyte exhibits excellent cycling stability with the capacity retention of the battery is 91.6% after 500 cycles. This work provides a viable solution for preventing batteries from thermal runaway triggered by overheating.

Potential-dependent superlubricity of stainless steel and Au(1 1 1) using a water-in-surface-active ionic liquid mixture

HypothesisThe friction and interfacial nanostructure of a water-in-surface-active ionic liquid mixture, 1.6 M 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate ([BMIm][AOT]), can be tuned by applying potential on Au(111) and stainless steel. ExperimentalAtomic force microscopy (AFM) was used to examine the friction and interfacial nanostructure of 1.6 M [BMIm][AOT] on Au(111) and stainless steel at different potentials. FindingsSuperlubricity (vanishing friction) is observed for both surfaces at OCP+1.0 V up to a surface-dependent critical normal force due to [AOT]− bilayers adsorbing strongly to the positively charged surface thus allowing AFM tip to slide over solution-facing hydrated anion charged groups. High-resolution AFM imaging reveals ripple-like features within near-surface layers, with the smallest amplitudes at OCP+1 V, indicating the highest structural stability and resistance to thermal fluctuations due to highly ordered boundary [AOT]− bilayers templating robust near-surface layers. Exceeding the critical normal force at OCP+1.0 V causes the AFM tip to penetrate the hydrated [AOT]− layer and slide over alkyl chains, increasing friction. At OCP and OCP-1.0 V, higher friction correlates with more pronounced ripples, attributed to the rougher templating [BMIm]+ boundary layer. Kinetic experiments show that switching from OCP-1.0 V to OCP+1.0 V achieves superlubricity within 15 s, enabling real-time friction control.

Competitive Effects of Anions on Protein Solvation by Aqueous Ionic Liquids.

The present study utilizes molecular dynamics simulations to examine how different anions compete for protein solvation in aqueous solutions of ionic liquids (ILs). Ubiquitin is used as model protein and studied in IL mixtures sharing the same cation, 1-ethyl-3-methylimidazolium (EMIM), and two different anions in the same solution, from combinations of dicyanamide (DCA), chloride (Cl), nitrate (NO3), and tetrafluoroborate (BF4). Our findings reveal that specific interactions between anions and the protein are paramount in IL solvation, but that combinations of anions are not additive. For example, DCA exhibits a remarkable ability to form hydrogen bonds with the protein, resulting in a significantly stronger preferential binding to the protein than other anions. However, the combination of DCA with NO3, which also forms hydrogen bonds with the protein, results in a smaller preferential solvation of the protein than the combination of DCA with chloride ions, which are weaker binders. Thus, combining anions with varying affinities for the protein surface modulates the overall ion accumulation through nonadditive mechanisms, highlighting the importance of the understanding of competition for specific interaction sites, cooperative binding, bulk-solution affinity, and overall charge compensations, on the overall solvation capacity of the solution. Such knowledge may allow for the design of novel IL-based processes in biotechnology and material science, where fine-tuning protein solvation is crucial for optimizing performance and functionality.

Electronically Controlled Broadband Terahertz Amplitude Modulator Based on Ionic Liquid/PEDOT:PSS:DMSO Composite Structure

Electronically controlled modulation devices operating in the terahertz (THz) band offer a crucial foundation for the integration and minimization of THz systems. In this work, we offer a broadband THz amplitude modulator that can be electrically controlled. The modulator is based on a composite structure made of ionic liquid and polymer mixture poly (3-ethoxythiophenyl): poly (4-phenylsulfonate) (PEDOT: PSS: DMSO). By applying merely +4 V excitation and -4 V turn-off voltage, a 40% amplitude modulation depth may be produced in the frequency region of 0.1-1.5 THz due to the joint action of electrons in the polymer and ions in the ionic liquid. The measurement of the resistance change of the polymer surface provides an explanation and confirmation of the mechanism of polymer action in this occurrence. This work provides a material selection for a simple preparation, inexpensive, and effective modulation of THz amplitude for an ionic liquid gate electronic controlled THz modulator. It is also expected that this work can be helpful for the miniaturization and integration development of THz modulators.

Novel application for graphene oxide-based ionanofluids in flat plate solar thermal collectors

This study presents new ionanofluids (INF) composed of 1-ethyl-3-methylimidazolium acetate ionic liquid (IL) and graphene oxide (GO) nanoparticles which have been assessed for the first time in an experimental flat plate solar thermal collector (FPSC). For this purpose, four types of INFs were synthesized, maintaining a constant concentration of GO nanoparticles dispersed in different base fluids: ionic liquid (IL/GO), a mixture of ionic liquid and water in varying concentrations (IL-water (75–25)%/GO and IL-water (50–50)%/GO), and water (Water/GO). These four INFs were characterized and their thermophysical and physicochemical properties were determined. The results indicated a 37.4% improvement in efficiency and up to a 2.5-fold increase in temperature within the collector when the IL was applied exclusively as the base fluid, compared to water. Furthermore, IL/GO demonstrated excellent stability, showing no signs of deterioration or nanoparticle precipitation two years after preparation and testing. These findings suggest that INFs based on IL and GO nanoparticles significantly enhance the efficiency of FPSC, presenting a promising option for solar energy applications and opening a new research avenue for INFs in the production of domestic hot water.

Aqueous Ionic Liquid Mixtures as Minimal Models of Lipid Bilayer Membranes.

We introduce aqueous ionic liquid (IL) mixtures, specifically mixtures of 1-butyl-3-imidazoliumtetrafluoroborate (BMImBF4), with water as a minimal model of lipid bilayer membranes. Imidazolium-based ILs are known to form clustered nanoscale structures in which local inhomogeneities, micellar or lamellar structures, are formed to shield hydrophobic parts of the cation from the polar cosolvent (water). To investigate these nanostructures, dynamic light scattering (DLS) on samples with different mixing ratios of water and BMImBF4 was performed. At mixing ratios of 50% and 45% (v/v), small and homogeneous nanostructures can indeed be detected. To test whether, in particular, these stable nanostructures in aqueous mixtures may mimic the effects of phospholipid bilayer membranes, we further investigated their interaction with myelin basic protein (MBP), a peripheral, intrinsically disordered membrane protein of the myelin sheath. Using dynamic light scattering (DLS), continuous wave (CW) and pulse electron paramagnetic resonance (EPR), and small-angle X-ray scattering (SAXS) on recombinantly produced, "healthy" charge variants rmC1WT and double cysteine variant C1S17CH85C, we find that the size and the shape of the determined nanostructures in an optimum mixture offer model membranes in which the protein exhibits native behavior. SAXS measurements illuminate the size and shape of the nanostructures and indicate IL-rich "beads" clipped together by functional MBP, one of the in vivo roles of the protein in the myelin sheath. All the gathered data combined indicate that the 50% and 45% aqueous IL mixtures can be described as offering minimal models of a lipid mono- or bilayer that allow native processing and potential study of at least peripheral membrane proteins like MBP.

Physicochemical properties of binary mixtures of cation-fluorinated ionic liquids with their non-fluorinated analogues

This work reports an investigation of the physicochemical properties (density, viscosity, refractive index and thermal stability) of four binary mixtures having a common acetate ([OAc]¯), trifluoromethanesulfonate ([OTf]¯) or bis(trifluoromethylsulfonyl)imide ([NTf2]¯) anion with either cation-fluorinated and non-fluorinated methylimidazolium (MIm) or pyridinium (Py) cations respectively, at various temperatures. The mixing behaviour of the binary mixtures was analysed by 1H and 19F Nuclear magnetic resonance (NMR) spectrometry, and the excess properties of the mixtures were calculated from the physicochemical data. The binary mixtures of fluorinated ionic liquids (FILs) with their non-fluorinated or alkyl-substituted analogues (AILs) showed an increase in density and viscosity but a decrease in refractive index with an increase in mole fraction of the pure FILs. The thermal stability of the AILs was higher than the FILs, however, an increase in the mole fraction of the pure FILs in the binary mixtures made a negligible impact on the thermal stability of the binary mixtures. These binary mixtures were found to deviate from ideal behaviour for the different physicochemical properties tending to vary between the extremes of the pure components. The large differences in properties of FILs compared with their non-fluorinated analogues were shown to be associated with the size of the fluorine atoms in the fluoro-alkyl chain, the tendency of the fluoro-alkyl chain to form aggregates with fluorinated anions, and the hydrogen bond acceptor strength of the anions. The excess properties were fitted to the Redlich-Kister polynomial equation, and no significant deviation was obtained. This study shows that the physicochemical properties of the fluorinated ionic liquids can conveniently be adjusted for specific applications by simply varying the amount of the cation-fluorinated component in binary mixtures.

Dicyanamide ionic liquid mixtures for curing and modifying flax-fiber reinforced epoxy resin composites

Epoxy composites reinforced with natural fibers are a research area that has been growing tremendously in recent years, with increasing reports providing a better understanding of the interactions within such structures, resulting in newer and more specialized applications. This article presents a comprehensive study on the design and application of ionic liquids (ILs) in the development of flax fiber-reinforced epoxy composites with tailored mechanical properties. Three distinct ILs, namely 1-hexyl-3-methylimidazolium dicyanamide [HMIM][DCA], 1-hexyl-1,4-diazabicyclo[2.2.2]octan-1-ium dicyanamide [DABCO-C6][DCA], and trimethyloctadecylammonium dicyanamide [N11118][DCA], were strategically engineered to incorporate longer carbon chains, with the primary objective of influencing the mechanical parameters of the resulting composites, specifically aiming for enhanced flexibility and resistance to bending and stretching. Using these designed ILs, two mixtures were developed and crafted to facilitate the effective curing of epoxy resin, which was examined using Differential Scanning Calorimetry (DSC). Investigation of the resin crosslinking process revealed that the mixtures of ILs exhibited a lower total enthalpy of thermal conversion than single-IL systems. Moreover, shifts in the polymerization onset temperatures were observed for the mixtures, with some systems displaying dual temperature peaks during crosslinking, indicative of potential parallel polymerization reactions.