Nonionic Liquids Research Articles

Application of non-ionic liquids-based modified dielectrics during electric discharge machining (EDM) of Ti6Al4V alloy to enhance machining efficiency and process optimization

The non-conventional manufacturing technologies are notorious when it comes to productivity and processing time in production-related industries. However, the aerospace and other high-end sectors enjoy another quality matrix of these processes and compromise on the processing time. For instance, the machinability of hard-to-cut materials such as Ti6Al4V aerospace alloy for micro-impressions is challenging and commonly carried out through non-conventional processes. Among these processes, the electric discharge machining (EDM) is famous for machining Ti6Al4V. In the current study, the EDM process is enhanced through modified dielectrics such as kerosene with non-ionic liquids (span 20, 60, and 80) and cryogenically treated tool electrodes (aluminum and graphite), and is compared to the conventional kerosene-based process. A three-phase experimental campaign is deployed to explore parametric effects including modified dielectric conditions (non-ionic liquid type and concentration), tool material, and machine parameter pulse ON:OFF time. A total of 60 experiments (54 modified dielectrics and 6 as baseline) were performed to explore process physics. The statistical analyses show that the unmodified process (kerosene dielectric-based) results in the least favorable results 0.58 mm3/min against cryo-graphite and 1.2 mm3/min against cryo-aluminum electrodes. However, the modified dielectrics outperform and improve process dynamics by altering dielectric conditions through hydrophilic-lipophilic balance. Surface morphological analysis shows significantly shallow craters on the machined surface showing evidence of effective flushing through a modified dielectric (S-20) as compared to a kerosene-based dielectric. A thorough microscopical, statistical, and scanning electron-based analysis is carried out to explain the process and correlate significant improvements.

Reducing micro-machining errors during electric discharge machining of titanium alloy using nonionic liquids

ABSTRACT The study employs nonionic liquids with cryogenically treated tool electrodes to investigate micro-machining errors. An extensive Full Factorial-based experimental campaign is executed involving unmodified process: 12 experiments (kerosene dielectric as baseline for improvement) and modified process: 108 experiments. In modified process, three distinct nonionic liquid types, their concentration, cryogenically treated electrodes, and pulse ON:OFF time are used. All the nonionic liquid-mixed dielectrics have shown noticeable improvement in terms of achieving low machining errors as compared to the conventional dielectric system. In unmodified process, the aluminum and graphite have produced micro machining errors 151.9 µm and 75 µm, respectively. The Desirability Function has recommended (experimentally validated 17.75 µm micro-machining error) the use of cryogenically treated graphite electrode with pulse ON:OFF time of 50:50 µSec and nonionic liquid S-60 with 25 g/L concentration to achieve minimum micro-machining errors with the highest desirability index of 98.60%.

In Silico Prediction of Eye Irritation Using Hansen Solubility Parameters and Predicted pKa Values.

An in silico method has been developed that permits the binary differentiation between pure liquids causing serious eye damage or eye irritation, and pure liquids with no need for such classification, according to the UN GHS system. The method is based on the finding that the Hansen Solubility Parameters (HSP) of a liquid are collectively important predictors for eye irritation. Thus, by applying a two-tier approach in which in silico predicted pKa values (firstly) and a trained model based solely on in silico-predicted HSP data (secondly) were used, we have developed, and validated, a fully in silico approach for predicting the outcome of a Draize test (in terms of UN GHS Cat. 1/Cat. 2A/Cat. 2B or UN GHS No Cat.) with high validation set performance (sensitivity = 0.846, specificity = 0.818, balanced accuracy = 0.832) using SMILES only. The method is applicable to pure non-ionic liquids with molecular weight below 500 g/mol, fewer than six hydrogen bond donors (e.g. nitrogen-hydrogen or oxygen-hydrogen bonds) and fewer than eleven hydrogen bond acceptors (e.g. nitrogen or oxygen atoms). Due to its fully in silico characteristics, this method can be applied to pure liquids that are still at the desktop design stage and not yet in production.

Diarylethene-Based Ionic Liquids: Synthesis and Photo-Driven Solution Properties.

In this work, the design and synthesis of a series of photochromic gemini diarylethene-based ionic liquids (GDILs) with different cationic motifs is reported. Several synthetic pathways were optimized for the formation of cationic GDILs with chloride as the counterion. The different cationic motifs were achieved through the N-alkylation of the photochromic organic core unit with different tertiary amines, including different aromatic amines such as imidazole derivatives and pyridinium, and other non-aromatic amines. These novel salts present surprising water solubility with unexplored photochromic features that broaden their known applications. The covalent attachment of the different side groups dictates their water solubility and differences upon photocyclization. The physicochemical properties of GDILs in aqueous and in imidazolium-based ionic liquid (IL) solutions were investigated. Upon irradiation with ultraviolet (UV) light, we have observed changes in the physico-chemical properties of distinct solutions containing these GDILs, at very low concentrations. More specifically, in aqueous solution, the overall conductivity increased with the time of UV photoirradiation. In contrast, in IL solution, these photoinducible changes are dependent on the type of ionic liquid used. These compounds can improve non-ionic and ionic liquids' solutions since we can change their properties, such as conductivity, viscosity or ionicity, only by UV photoirradiation. The electronic and conformational changes associated with these innovative stimuli GDILs may open new opportunities for their use as photoswitchable materials.

Revealing the Structural Evolution of Green Rust Synthesized in Ionic Liquids by In Situ Molecular Imaging

AbstractIonic liquids are green solvents that have wide applications in material synthesis, catalysis, and separation. A model switchable ionic liquid (SWIL) consisting of 1,8‐diazabicycloundec‐7‐ene (DBU) and 1‐hexanol with carbon dioxide (CO2) as the trigger gas is chosen to synthesize nanocrystalline green rust. Under anoxic conditions, by adding iron (II) acetate (Fe(C2H3O2)2) and methanol to the degassed SWIL, a nanoparticulate green rust with carbonate (nano‐GR) is synthesized. More importantly, the molecular structural change of the ionic liquid resulting in green rust crystallines is first characterized using in situ liquid using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) coupled with the system for analysis at the liquid vacuum interface (SALVI), a vacuum compatible microfluidic reactor in this work. Dimers and ionic clusters consisting ferric and ferrous ions are identified in liquid ToF‐SIMS spectra. Spectral principal component analysis is used to confirm that these ion pairs including dimers and cluster ions are different from nonionic liquids. The results show that liquid ToF‐SIMS can be a useful tool to study complex liquids at the molecular level providing insights into predicative synthesis of nanomaterials using environmentally friendly green solvents and giving unique visualization of the evolving material interface due to nucleation.

First-principles modeling of chemistry in mixed solvents: Where to go from here?

Mixed solvents (i.e., binary or higher order mixtures of ionic or nonionic liquids) play crucial roles in chemical syntheses, separations, and electrochemical devices because they can be tuned for specific reactions and applications. Apart from fully explicit solvation treatments that can be difficult to parameterize or computationally expensive, there is currently no well-established first-principles regimen for reliably modeling atomic-scale chemistry in mixed solvent environments. We offer our perspective on how this process could be achieved in the near future as mixed solvent systems become more explored using theoretical and computational chemistry. We first outline what makes mixed solvent systems far more complex compared to single-component solvents. An overview of current and promising techniques for modeling mixed solvent environments is provided. We focus on so-called hybrid solvation treatments such as the conductor-like screening model for real solvents and the reference interaction site model, which are far less computationally demanding than explicit simulations. We also propose that cluster-continuum approaches rooted in physically rigorous quasi-chemical theory provide a robust, yet practical, route for studying chemical processes in mixed solvents.

Connection between dielectric constant and total number of hydrogen-bond groups per cation–anion pair in ionic liquids

This paper reports a quantitative connection between the dielectric constant and calculated total number of hydrogen-bond groups per cation–anion pair for 44 ionic liquids, including 15 ionic liquids with high dielectric constants exceeding 20. The total number of hydrogen-bond groups per cation–anion pair was equal to the addition of the hydrogen-bond group number per cation and per anion. The methylene group could reduce the group number capable of forming hydrogen bonds, and one methylene group caused a decrease of 1 hydrogen-bond number. Regardless of whether a liquid was ionic or non-ionic liquid, approximately linear relationship were observed between dielectric constant and total hydrogen-bond number per molecule. For ionic liquids, an increase of 1 in the total number of hydrogen-bond groups per cation–anion pair resulted in an increase of approximately 8.5 in the dielectric constant. For non-ionic liquids, the value was approximately 21.9. The average molar density of nine hydrogen-bonded ionic liquids with high dielectric constants was 9.3 × 103 mol/m3, while the average molar density of eight non-ionic liquids with hydrogen-bonds was 21.1 × 103 mol/m3. The 21.1 molar density coefficient of the non-ionic liquids was almost equal to the 21.9 coefficient in the dielectric constant equation, and the 9.3 molar density coefficient of the ionic liquids was very close to the 8.5 coefficient in its dielectric constant equation. This result indicated that the effect mechanisms of the intermolecular hydrogen-bond structure on dielectric constant were similar for the two types of liquids.

Non-Ionic Deep Eutectic Liquids: Acetamide-Urea Derived Room Temperature Solvents.

A family of non-ionic deep eutectic liquids has been developed based upon mixtures of solid N-alkyl derivatives of urea and acetamide that in some cases have melting points below room temperature. The eutectic behaviour and physical characteristics of a series of eleven eutectic mixtures are presented, along with a molecular dynamics study-supported hypothesis for the origin of the non-ideal mixing of these substances. Their use as solvents in applications ranging from natural product extraction to organic and polymer synthesis are demonstrated.

Optothermophoretic Manipulation of Colloidal Particles in Nonionic Liquids.

The response of colloidal particles to a light-controlled external temperature field can be harnessed for opto-thermophoretic manipulation of the particles. The thermoelectric effect is regarded as the driving force for thermophoretic trapping of particles at the light-irradiated hot region, which is thus limited to ionic liquids. Herein, we achieve opto-thermophoretic manipulation of colloidal particles in various non-ionic liquids, including water, ethanol, isopropyl alcohol and 1-butanol, and establish the physical mechanism of the manipulation at the molecular level. We reveal that the non-ionic driving force originates from a layered structure of solvent molecules at the particle-solvent interface, which is supported by molecular dynamics simulations. Furthermore, the effects of hydrophilicity, solvent type, and ionic strength on the layered interfacial structures and thus the trapping stability of particles are investigated, providing molecular-level insight into thermophoresis and guidance on interfacial engineering for optothermal manipulation.

Effect of carbon nanofibers on mechanical and electrical behaviors of acrylonitrile‐butadiene rubber composites

Recently, carbon nanofibers have become an innovative reinforcing filler that has drawn increased attention from researchers. In this work, the reinforcement of acrylonitrile butadiene rubber (NBR) with carbon nanofibers (CNFs) was studied to determine the potential of carbon nanofibers as reinforcing filler in rubber technology. Furthermore, the performance of NBR compounds filled with carbon nanofibers was compared with the composites containing carbon black characterized by spherical particle type. Filler dispersion in elastomer matrix plays an essential role in polymer reinforcement, so we also analyzed the influence of dispersing agents on the performance of NBR composites. We applied several types of dispersing agents: anionic, cationic, nonionic, and ionic liquids. The fillers were characterized by dibutylphtalate absorption analysis, aggregate size, and rheological properties of filler suspensions. The vulcanization kinetics of rubber compounds, crosslink density, mechanical properties, hysteresis, and conductive properties of vulcanizates were also investigated. Moreover, scanning electron microscopy images were used to determine the filler dispersion in the elastomer matrix. The incorporation of the carbon nanofibers has a superior influence on the tensile strength of NBR compared with the samples containing carbon black. It was observed that addition of studied dispersing agents affected the performance of NBR/CNF and NBR/carbon black materials. Especially, the application of nonylphenyl poly(ethylene glycol) ether and 1‐butyl‐3‐methylimidazolium tetrafluoroborate contributed to enhanced mechanical properties and electrical conductivity of NBR/CNF composites.

Research on the strengths of electrostatic and van der Waals interactions in ionic liquids

The special properties of ionic liquids are due to the simultaneous presence of Coulombic and van der Waals forces. Evaluation of their interaction strengths is a basic work for explaining the macroscopic physical properties of ionic liquids, understanding the molecular dynamics and microstructure of ionic liquids, and assessing the binding force induced by ions in biological systems. In this paper, a modified Coulomb's law was constructed to calculate the average electrostatic force in ionic liquids through treating an ionic liquid molecule as two charges separated by some organic groups and taking these organic groups as an organic molecule. The modified Coulomb's law was verified with the surface tension data of 117 non-ionic liquids and 153 ionic liquids. According to the modified Coulomb's law, the average strengths of the electrostatic and van der Waals interactions between a pair of cation-anion in the 153 ionic liquids were almost equal, which were about 20pN.

Ionic liquids and their bases: Striking differences in the dynamic heterogeneity near the glass transition.

Ionic liquids (ILs) constitute an active field of research due to their important applications. A challenge for these investigations is to explore properties of ILs near the glass transition temperature Tg, which still require our better understanding. To shed a new light on the issues, we measured ILs and their base counterparts using the temperature modulated calorimetry. We performed a comparative analysis of the dynamic heterogeneity at Tg for bases and their salts with a simple monoatomic anion (Cl–). Each pair of ionic and non-ionic liquids is characterized by nearly the same chemical structure but their intermolecular interactions are completely different. We found that the size of the dynamic heterogeneity of ILs near Tg is considerably smaller than that established for their dipolar counterparts. Further results obtained for several other ILs near Tg additionally strengthen the conclusion about the relatively small size of the dynamic heterogeneity of molecular systems dominated by electrostatic interactions. Our finding opens up new perspectives on designing different material properties depending on intermolecular interaction types.

Design and Control of Ionic Liquid‐Catalyzed Reactive Distillation for n‐Butyl Acetate Production

AbstractA simulation study of n‐butyl acetate production with the [Hpy][HSO4] ionic liquid catalyst was performed. Due to the lack of phase equilibrium data, the binary interaction parameters of the NRTL model for ionic liquid and reactive species were calculated by the COSMO‐RS technique. A reactive distillation process with recycled ionic liquid stream was proposed, and the column configuration was optimized by minimization of the total annual capital. The novel process is considerably efficient and economic compared to the traditional reactive distillation process of nonionic liquids. With the steady‐state parameters, a plant‐wide control structure was further developed to evaluate the robustness of the control system by exerting the disturbances of feed flow rate and feed composition. Dynamic simulation results suggest that the control scheme with a composition controller is timely and effective.

Flow-induced voltage generation in non-ionic liquids over monolayer graphene

To clarify the origin of the flow-induced voltage generation in graphene, we prepared a new experimental device whose electrodes were aligned perpendicular to the flow with a non-ionic liquid. We found that significant voltage in our device was generated with increasing flow velocity, thereby confirming that voltage was due to an intrinsic interaction between graphene and the flowing liquid. To understand the mechanism of the observed flow-induced voltage generation, we systematically varied several important experimental parameters: flow velocity, electrode alignment, liquid polarity, and liquid viscosity. Based on these measurements, we suggest that polarity of the fluid is a significant factor in determining the extent of the voltage generated, and the major mechanism can be attributed to instantaneous potential differences induced in the graphene due to an interaction with polar liquids and to the momentum transferred from the flowing liquid to the graphene.

The Effect of Carbon Fillers on Elastomer Composite Properties

The aim of this work was to obtain elastomer composite filled with carbon fillers with different structure. Three types of carbon black were used as reinforcing fillers: FEF N550, Colour Black FW200, Printex XE2B. In order to improve dispersion of fillers, different dispersing agents were used: anionic, cationic, nonionic and ionic liquids. As an elastomer matrix the acrylonitrile-butadiene rubber (NBR) was used. The fillers were characterized by dibutylphtalate (DBP) absorption analysis, aggregates size, rheological properties of filler suspensions and Zeta potential analysis. The compounding was carried out in a laboratory rolling mill. Samples were prepared through the vulcanization process at 160°C. The vulcanization kinetics of rubber compounds, crosslink density, mechanical properties, hysteresis losses, conductive and thermal properties of vulcanizates were also measured. In order to characterize filler dispersion in elastomer matrix the SEM images were obtained.

Solubilization and stabilization of fullerene C60 in presence of poly(vinyl pyrrolidone) molecules in water

Solubilizing C60 molecules in an aqueous medium is highly imperative in processing them in different forms of ionic or nonionic liquids, nanofluids, films and other derivatives. In this investigation, we report a facile chemical route using polymer molecules of poly(vinyl pyrrolidone) (PVP) which mediate C60 molecules dissolving in water in a stable solution at room temperature. Poly(vinyl pyrrolidone) molecules, soluble in water as well as many organic liquids such as n-butanol, ethanol, or DMF, can be useful for transferring C60 molecules from a non-aqueous to an aqueous system. A broad optical absorption arises over 270–520 nm when C60 molecules are dissolved in water, 0.001–0.065 g/L in presence of 20–120 g/L PVP molecules. It consists of a strong π → π* absorption band (relatively sharp) lying at 294 nm in C(sp2) electrons from PVP-surface modified C60 molecules followed by a broad charge transfer band which extends up to 520 nm. Upon a suitable surface modification, the C60 molecules conquer enhanced optical absorption in both kinds of the bands. Dynamic light scattering reveals an average hydrodynamic length 181.5 nm and a polydispersity index 0.506 after a typical loading 0.065 g/L C60. A zeta potential −8.3 mV with a surface conductivity 0.064 mS/cm at 6.5 pH describes a negatively charged surface structure, showing an n-electron transfer from C=O (PVP) to a nanosurface in surface modified C60 molecules in a weak donor–acceptor complex. Water soluble C60 in presence of a biocompatible compound like PVP is useful for biological, medicinal, and other applications.

“Amphiphilic” Ionic Liquid in a Mixture of Nonionic Liquids: Theoretical Study

We use a Flory-Huggins type approach to describe a two-phase system consisting of nonionic components A and B that are incompatible with each other and of an ionic liquid (IL). The anions and the cations of the IL are considered as independent components and are assumed to have different affinities for A and B. We show that an up to several hundreds molecules thick double electrostatic layer is formed by the IL at the phase boundary, and the surface tension of the boundary happens to be smaller in the case of the three-component system than in the case of a two-component system consisting of the components A and B only; i.e., the IL plays the role of a surfactant. We investigate by means of a numerical calculation the full range of possible IL concentrations in the bulk of the two phases and also consider analytically the case of the low IL concentrations. The results obtained by means of the two methods are in perfect agreement.

Influence of Polarization on Structural, Thermodynamic, and Dynamic Properties of Ionic Liquids Obtained from Molecular Dynamics Simulations

Utilizing the transferable, quantum-chemistry-based, Atomistic Polarizable Potential for Liquids, Electrolytes, & Polymers (APPLE&P) force field, we have systematically investigated the influence of polarization effects on the accuracy of properties predicted from molecular dynamics simulations of various room temperature ionic liquids (ILs). Simulations of ILs in which the atom-based polarizability was set to zero for all atoms (nonpolarizable APPLE&P potential) resulted in changes in thermodynamic and dynamic properties from those predicted by the polarizable APPLE&P potential that are qualitatively different from changes observed for nonionic liquids. Investigation of structural and dynamical correlations using both the polarizable and nonpolarizable versions of APPLE&P allowed us to obtain a mechanistic understanding of the influence of polarization on dynamics in the ILs investigated. Additionally, the Force Matching (FM) approach was employed to systematically obtain nonpolarizable two-body force fields for several ILs that reproduce as accurately as possible intermolecular forces predicted by the polarizable model. Unlike water, for which the FM approach was found to yield an accurate representation of the liquid phase structure predicted by a polarizable model, the FM approach does not result in a two-body potential that accurately reproduces either structure or dynamics predicted by the polarizable IL model.

Elastomers Containing Fillers with Magnetic Properties

Composites of rubbers such as ethylene – propylene and acrylonitrile – butadiene with micro size Fe¬3O4, Fe2O3, and nano size Fe3O4 as the fillers were tested. Iron oxides were found to be active fillers which improved mechanical properties of elastomers. Additionally, they also changed their magnetic properties. Furthermore, the surface of micro size Fe3O4 was modified to upgrade mechanical properties of the vulcanizates. Itaconic acid, methacryloxypropyltrimethoxysilane and monododecyl maleate were used as modifying agents. To improve dispersion of applied fillers in polymers matrix, non-ionic (NF-PEG), anionic (calcium stearate ), cationic (DTAB, DTAC, DDAB, CTAD) and ionic liquids (HMIMBF4, BMIMPF6, OMIMPF6) were used. It was observed that both non-modified and modified micro iron oxides and nano iron oxides improved the properties of the vulcanizates the most effectively.

Reversible, Room-Temperature, Chiral Ionic Liquids. Amidinium Carbamates Derived from Amidines and Amino-Acid Esters with Carbon Dioxide

The properties of a new class of chiral, room-temperature, ionic liquids (RTILs) are described. They are made from easily synthesized, readily available materials and can be transformed reversibly to their nonionic liquid states. The nonionic liquids consist of neat equimolar mixtures of a N‘-alkyl-N,N-dimethylacetamidine (L) and an alkyl ester of a naturally occurring amino acid (n). When exposed to 1 atm of CO2 gas, the L/n solutions become cationic−anionic pairs, amidinium carbamates. Of the 50 L/n combinations examined, all except those involving the methyl ester of tyrosine (which was immiscible with the amidines) form RTIL states under CO2 atmospheres, and several remain liquids to at least −18 °C. Heating the ionic liquids in air at ca. 50 °C or bubbling N2 gas through them at ambient temperatures for protracted periods displaces the CO2 and re-establishes the nonionic L/n states. As an example of the changes effected by cycling between the two liquid states, a spectroscopic probe, 1-(p-dimethylami...