Short Alkyl Chain Research Articles

Self-Assembly of a Series of Carbazole-Based Vinyl-benzoxazole Derivatives in Gel Phases.

A series of carbazole-based vinyl-benzoxazole derivatives have been synthesized in order to verify whether X-ray diffraction (XRD) simulation can give more information about intermolecular stacking in the gel phase. It was found that their gelation capabilities were strongly dependent on the length of the alkyl chain. The compounds with shorter alkyl chains have lower critical gelation concentrations (CGCs) in nonpolar alkane and alcohols with longer carbon chains. On the other hand, compounds with long alkyl chains presented small CGCs in polar methanol. Powder XRD structure solution gave more information about intermolecular stacking than the traditional way of analyzing diffraction peaks to derive approximate molecular stacking patterns. The results verified that gelators had a similar head-to-tail π-stacking between aromatic groups in gel phases although different slipping angles existed. Moreover, ordered stacking between the alkyl chains was also present.

Adverse cardiovascular effects of long-term exposure to diethyl phthalate in the rat aorta

Phthalates are classified as priority environmental pollutants, since they are ubiquitous in the environment, have endocrine disrupting properties and can contribute to impaired health. Used primarily in personal care products and excipients for pharmaceuticals, diethyl phthalate (DEP) is a short-chain alkyl phthalate that has been linked to decreased blood pressure, glucose tolerance, and increased gestational weight gain in humans, while in animals it has been associated with atherosclerosis and metabolic syndrome. Although all these findings are related to risk factors or cardiovascular diseases, DEP's vascular impacts still need to be clarified. Thus, performing ex vivo and in vitro experiments, we aimed to understand the vascular DEP effects in rat. To evaluate the vascular contractility of rat aorta exposed to different doses of DEP (0.001–1000 μM), an organs bath was used; and resorting to a cell line of the rat aorta vascular smooth muscle, electrophysiology experiments were performed to analyse the effects of a rapid (within minutes with no genomic effects) and a long-term (24 h with genomic effects) exposure of DEP on the L-type Ca2+ current (ICa,L), and the expression of several genes related with the vascular function. For the first time, vascular electrophysiological properties of an EDC were analysed after a long-term genomic exposure. The results show a hormetic response of DEP, inducing a Ca2+ current inhibition of the rat aorta, which may be responsible for impaired cardiovascular electrical health. Thus, these findings contribute to a greater scientific knowledge about DEP's effects in the cardiovascular system, specifically its implications in the development of electrical disturbances like arrhythmias and its possible mechanisms.

Evaluation of water + imidazolium ionic liquids as working pairs in absorption refrigeration cycles

Ionic Liquids (ILs) have been proposed as alternative absorption media for water in absorption refrigeration cycles to replace the currently used lithium bromide, which suffers from problems like crystallization and corrosiveness. This work investigates the use of imidazolium based ionic liquids as water absorbents in absorption refrigeration cycles. A predictive procedure is followed for calculating the parameters that mostly affect the performance of the cycle, that is the Vapor-Liquid Equilibrium (VLE) of the working pair and its heat capacity: UNIFAC is employed for the VLE calculations while a new predictive method has been developed for the heat capacity of the ILs. The effect of the alkyl chain length of the cation and the type of the anion that compose the IL is investigated, and it is shown that ILs consisting of imidazolium cation with short alkyl chain and the anions [Cl] and [DMP] exhibit the best performance in terms of Coefficient of Performance (COP) and circulation ratio (f). Comparison with the conventional LiBr absorbent indicates that the best ILs exhibit higher COP values but higher f ratios as well. Also, double cycle configurations are studied revealing the major effect of the supplied heat temperature on COP, even for the higher temperatures, compared to the single effect one. Finally, it is shown that there is a clear correlation between the COP of the refrigeration cycle and the product of the circulation ratio and the specific heat capacity of the strong solution, which is proposed in this work as a new reliable index for screening different ILs as absorbents, without the necessity of solving the mass and energy balances of the cycle.

Impact of 2D Ligands on Lattice Strain and Energy Losses in Narrow‐Bandgap Lead–Tin Perovskite Solar Cells

AbstractMixed lead and tin (Pb/Sn) hybrid perovskites exhibit a great potential in fabricating all‐perovskite tandem devices due to their easily tunable bandgaps. However, the energy deficit and instability in Pb/Sn perovskite solar cells (PSCs) constrain their practical applications, which renders defect passivation engineering indispensable to develop highly efficient and long‐term stable PSCs. Herein, the mechanisms of strain tailoring and defect passivation in Pb/Sn PSCs by 2D ligands are investigated. The 2D ligands include electroneutral cations with long alkyl chain (LAC), iodates with relatively short alkyl chain (SAC) and their mixtures. This study reveals that LAC ligands facilitate the relaxation of tensile strain in perovskite films while SAC ligands cause strain buildup. By mixing LAC/SAC ligands, tensile strain in perovskite films can be balanced which improves solar cell performance. PSCs with admixed β‐guanidinopropionic acid (GUA)/phenethylammonium iodide (PEAI) exhibit enhanced open circuit voltage and fill factor, which is attributed to reduced nonradiative recombination losses in the bulk and at the interfaces. Furthermore, the operational stability of PSCs is slightly improved by the mixed 2D ligands. This work reveals the mechanisms of 2D ligands in strain tailoring and defect passivation toward efficient and stable narrow‐bandgap PSCs.

Interfacial Interaction in Colloidal Heteronanostructures of Tb3+-Complex and Eu3+-Doped Nanosheets: Implications for Bioprobes

It is essential for luminescent materials to be compatible with complex bioenvironments when used for probing biological events. Förster resonance energy transfer (FRET) is a common process in gaining enhanced luminescence signals, in which the interaction between the donor and acceptor plays a decisive role in the optical properties of heterostructured bioprobes. Yet systematic investigations on the gradient amphiphilic and electrostatic interaction effect on luminescence in a complex environment are scarce. Heteronanostructures of Tb(C12H8N2)2(NO3)3 nanocrystals and Eu3+-doped oxide nanosheets in various solutions with varied double electric layers and amphiphilic capacities are chosen for the investigation. It is found that a complex redox process takes place and an interfacial Tb–O bond is formed during preparation of the heteronanostructures. According to the decay dynamics of Tb3+ and Eu3+ emission of the heteronanostructures in various amphiphilic alcohol solvents, the interfacial Tb3+ → Eu3+ energy transfer efficiency apparently displays an extraordinary dependence on alkyl chain length after excluding the refractive index effect, while the zeta potential data suggest that the interfacial electrostatic force on the heteronanostructures should be dominant via the electric double layer in alcohol solvents with short alkyl chain. As the length of alkyl chain increases, the amphiphilic force on the heteronanostructures with amphiphilic Tb(phen)2(NO3)3 and hydrophilic Eu3+-doped nanosheets tends to be overwhelming. These competitive forces strengthen the interaction between Tb3+ and Eu3+ and result in enhancement of the interfacial Tb3+ → Eu3+ energy transfer efficiency. The research helps design potential new bioprobes concerning the interfacial interaction in amphiphilic and salty biosystems.

Coordination-Induced Multivalent Self-Assembling Catalysts for Spectral Sensing Zn2+ with High Selectivity and Sensitivity.

The introduction of signal amplification to molecular spectral sensing systems is an intriguing topic in supramolecular analytical chemistry. In this study, click chemistry was used to generate a triazole moiety to bridge with a long hydrophobic alkyl chain (Cn) and another short alkyl chain (Cm) bearing a 1,4,7-triazacyclonane (TACN) group for efficiently generating a self-assembling multivalent catalyst, Cn-triazole-Cm-TACN·Zn2+ (n and m represent the carbon numbers of both alkyl chains, respectively; n = 16, 18, and 20; m = 2 and 6), to catalyze the hydrolysis of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNPP) when Zn2+ was added. The triazole moiety introduced adjacent to the TACN group plays an important role in improving the selectivity of Zn2+ because the triazole moiety can participate in the coordination interaction between the Zn2+ and neighboring TACN group. The supplementary triazole complexing increases the space requirement for coordinated metal ions. This catalytic sensing system also shows high sensitivity, with a favorable limit of detection down to 350 nM, even if only UV-vis absorption spectra rather than more sensitive fluorescence techniques were used for signaling, and can be used to determine the concentration of Zn2+ in tap water, which demonstrates the practical application feasibility.

Demulsification of Crude Oil Emulsions Using Versatile and Eco-Friendly Demulsifiers Based on Cellulose Decorated with Imidazolium-Bearing Triazole Moiety.

Water in the crude oil forms emulsions that must be broken before refining processes. Here, the novel and versatile derivatives of imidazolium ionic liquids (ILs) containing triazole moiety [SIm-TazCn][Br] were synthesized via click chemistry and then grafted onto the cellulose (CEL) to prepare eco-friendly demulsifiers for breaking water-in-oil (W/O) emulsions. The prepared compounds with two kinds of alkyl chains named CEL[SIm-TazC6][Br] and CEL[SIm-TazC10][Br] were characterized and employed for demulsifying W/O (30:70 and 50:50 vol %) emulsions. Also, the effect of the type and concentration of each demulsifier on the phase separation and dehydration efficiency (DE) were investigated through the bottle test. According to the bottle test results, the CEL[SIm-TazC6][Br] derivative at 4000 ppm showed a good DE of 79% after 5 min, which increased to 82% after 24 h. The interfacial tension (IFT) of derivatives at different concentrations was measured. The minimum IFT value of 16.3 mN/m was obtained for CEL[SIm-TazC6][Br] with a shorter alkyl chain at 4000 ppm after 24 h. The green and efficient CEL-based surfactants significantly demulsified the W/O emulsions because of the collaboration between imidazolium and triazole moieties.

Alkyl-substituted bipyridyl platinum (II) complexes bearing alkynyl-naphthalimide ligands: Synthesis, photophysical properties, and tunable aggregation-induced emission activity

Different alkyl chains were introduced into alkynyl-naphthalimide ligands and bipyridine ligands to synthesize five platinum complexes, their structures were characterized and the photophysical properties were systematically investigated. It was found that the introduction of alkyl chains had no obvious effect on the absorption and emission of these complexes in dilute solution, while influence aggregation-induced emission activity in aggregated state. In the mixed solvent system of tetrahydrofuran and ethylene glycol, the shorter alkyl chains on the bipyridine ligands strengthen the aggregation-induced phosphorescence emission (AIPE) properties of complexes, however, the introduction of different alkyl chains on the alkynyl-naphthalimide ligands makes no difference on their AIPE properties. Combining the single crystal results and Hirshfled surface analysis, the photophysical properties of these complexes in aggregated state were affected by the stacking modes, which is due to the different interactions. This research may broaden the scope for the design of multi-functional materials adopting different aggregation states.

A Comparison of Interpolyelectrolyte Complexes (IPECs) Made from Anionic Block Copolymer Micelles and PDADMAC or q-Chitosan as Polycation.

Block copolymers synthesized via Atom Transfer Radical Polymerization from alkyl acrylate and t-butyl acrylate and the subsequent hydrolysis of the t-butyl acrylate to acrylic acid were systematically varied with respect to their hydrophobic part by the variation in the alkyl chain length and the degree of polymerisation in this block. Depending on the architecture of the hydrophobic part, they had a more or less pronounced tendency to form copolymer micelles in an aqueous solution. They were employed for the preparation of IPECs by mixing the copolymer aggregates with the polycations polydiallyldimethylammonium chloride (PDADMAC) or q-chit. The IPEC structure as a function of the composition was investigated by Static Light and Small Angle Neutron Scattering. For weakly-associated block copolymers (short alkyl chain), complexation with polycation led to the formation of globular complexes, while already existing micelles (long alkyl chain) grew further in mass. In general, aggregates became larger upon the addition of further polycation, but this growth was much more pronounced for PDADMAC compared to q-chit, thereby leading to the formation of clusters of aggregates. Accordingly, the structure of such IPECs with a hydrophobic block depended largely on the type of complexing polyelectrolyte, which allowed for controlling the structural organisation via the molecular architecture of the two oppositely charged polyelectrolytes.

Slurry-Phase Hydrogenation of Different Asphaltenes to Liquid Fuels on Dispersed MoS2 Nanocatalysts.

Asphaltene, the most complex and recalcitrant fraction of heavy oil, was investigated in this study to gain new insights into its structure and reactivity. Two types of asphaltenes, ECT-As and COB-As, were extracted from ethylene cracking tar (ECT) and Canada's oil sands bitumen (COB), respectively, and used as reactants for slurry-phase hydrogenation. Characterization of ECT-As and COB-As was carried out by a combination of techniques, including XRD, elemental analysis, simulated distillation, SEM, TEM, NMR, and FT-IR, to gain insights into their composition and structure. A dispersed MoS2 nanocatalyst was used to study the reactivity of ECT-As and COB-As under hydrogenation conditions. The results showed that under optimal catalytic conditions, the vacuum residue content of hydrogenation products could be reduced to less than 20%, and the products contained over 50% light components (gasoline and diesel oil), indicating that ECT-As and COB-As were effectively upgraded. The characterization results indicated that ECT-As contained a higher aromatic carbon content, shorter alkyl side chains, fewer heteroatoms, and less highly condensed aromatics than COB-As. The light components (gasoline and diesel oil) of ECT-As hydrogenation products mainly consisted of aromatic compounds with 1-4 rings, with the alkyl chains mainly composed of C1-C2, while light components of COB-As hydrogenation products were mainly composed of aromatic compounds with 1-2 rings and C11-C22 paraffins. The characterization of ECT-As and COB-As and their hydrogenation products revealed that ECT-As was an "archipelago type" asphaltene, composed of multiple small aromatic nuclei interconnected through short alkyl chains, while COB-As was an "island type" asphaltene, with long alkyl chains connected to aromatic nuclei. It is suggested that the structure of asphaltene has a significant impact on both its reactivity and product distribution.

A good and bad aggregation: Effect of imidazolium- and cholinium-based ionic liquids on the thermal stability of bovine serum albumin

The present work describes the effect of imidazolium- and cholinium-based ionic liquids (ILs) on the thermal stability, binding and aggregation of bovine serum albumin (BSA). The studied ILs include choline chloride [Ch][Cl], choline dihydrogenphosphate [Ch][DHP], choline acetate [Ch][OAc], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF4] 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO], 1-butyl-3-methylimidazolium acetate [BMIM][OAc], and 1-butyl-3-methylimidazolium methanesulfonate [BMIM][CH3SO3]. The state of BSA in presence of ILs was assessed by circular dichroism (CD), temperature dependent circular dichroism, fluorescence spectroscopy, and dynamic light scattering (DLS). The thermal stability of BSA in presence of ILs increased (above 85 °C) in all studied ILs except [OMIM][BF4]. Differences of binding ILs with BSA depending on alkyl chain length were estimated, the probable binding modes were identified using molecular docking. The influence of ILs on the aggregation of BSA at different temperatures was established. It was found that the ILs with short alkyl chain length (up to butyl) promote aggregation of the native form of BSA increasing its thermal stability.

Degradation of dibutyl phthalate and diethyl phthalate by indigenous isolate Bacillus sp. MY156

Dibutyl phthalate (DBP) and diethyl phthalate (DEP) are among the most extensively utilized plasticizers and widely exist in the environment causing adverse effect on human health. Previous studies on these phthalic acid esters (PAEs) biodegradation mainly involved individual substrates. However, these contaminants are more possible existed in mixtures. This work explored the biodegradation of DBP and DEP and their interactions using the indigenous isolate Bacillus sp. MY156. The results demonstrate DBP could be completely degraded by strain MY156 with high efficiency, while DEP showed relatively lower removal efficiency (72%) in 120 h. The binary substrate removal results revealed the coexistence of DBP and DEP had no significant influence on the degradation of each under the optimal pH and temperature. Nevertheless, slight retardation of the removal efficiency for DEP noticed as co-existed with DBP demonstrated their removal was possibly affected through the substrate competition. The dehydrogenase activity assay illustrated the behaviors of dehydrogenases caused by long-side chains PAEs were higher than PAEs with shorter alkyl chains. The isolate Bacillus sp. MY156 showed a positive utilization potentiality for bioremediation of PAEs-polluted environment.

Using dicationic ionic liquids to upgrade the cytotoxicity and solubility of poorly water-soluble drugs

New dicationic ionic liquids (DcILs) based on carboxylic acid-derived, N-acetyl amino acid-derived or bromide anions, and ammonium cations were synthesized and characterized. DcILs were employed as co-solvents to improve the solubility of ibuprofen and ketoprofen belonging to BCS class II. These DcILs demonstrated to be less cytotoxic towards fibroblasts L929 cells and contributed to an augment in the solubility of both drugs when compared with monocationic ionic liquids (McILs). The cytotoxic profile of some of these ILs was established, and when the linker between two ammonium cations was an ether group or a short alkyl chain an IC50 higher than 200 mM for fibroblasts L929 cells was achieved.The anion structure showed to be a key factor in the solubility of both drugs, being the family of carboxylic acid-derived, the one that presented the most significant effect, followed by N-acetyl amino acid-derived and finally bromide. The two dimensional 1H1H– NOESY NMR spectra showed the interaction between the IL and the two oral drugs, responsible for the improvement of their solubility. The lipophilicity (logP) of ibuprofen and ketoprofen reduced in the presence of these new DcILs.

Charge Injection and Energy Transfer of Surface-Engineered InP/ZnSe/ZnS Quantum Dots.

Surface passivation is a critical aspect of preventing surface oxidation and improving the emission properties of nanocrystal quantum dots (QDs). Recent studies have demonstrated the critical role of surface ligands in determining the performance of QD-based light-emitting diodes (QD-LEDs). Herein, the underlying mechanism by which the capping ligands of InP/ZnSe/ZnS QDs influence the brightness and lifetime of the QD-LEDs is investigated. The electrochemical results demonstrate that highly luminescent InP/ZnSe/ZnS QDs exhibit modulated charge injection depending on the length of the surface ligand chains: short alkyl chains on the ligands are favorable for charge transport to the QDs. In addition, the correlation between the spectroscopic and XRD analyses suggests that the length of the ligand chain tunes the ligand-ligand coupling strength, thereby controlling the inter-QD energy transfer dynamics. The present findings shed new light on the crucial role of surface ligands for InP/ZnSe/ZnS QD-LED applications.

Columnar Liquid Crystalline Glasses by Combining Configurational Flexibility with Moderate Deviation from Planarity: Extended Triaryltriazines.

Triply phenanthryl- and tetrahelicenyl-substituted triazine-hexaalkyl esters with short alkyl chains show glass transitions conveniently above room temperature within the hexagonal columnar liquid crystalline state, resulting in a solid columnar order at room temperature. As the hexagonal columnar mesophase is easily aligned with the director perpendicular to a solid substrate, such glassy columnar liquid matrices are aimed at for the orientation of guest emitters, to obtain anisotropic emission. A condition for face-on alignment on substrates are attainable melting and clearing temperatures, which is achieved with the moderately nonplanar tetrahelicenyl derivatives in spite of their short alkyl periphery. An unusual phase transition between two columnar mesophases of same hexagonal symmetry, but very different long-distance regularity of the column lattice, is found in one phenanthryl homolog.

Investigation the effect of different ionic liquids based-aryl imidazole on the onset precipitation of asphaltene

Precipitation and deposition of asphaltene are considered as catastrophic issues facing the petroleum industry. Asphaltene deposition mainly occurs at variety places such as formation pore spaces, pumps, pipelines, wellbore, wellhead, tubing, surface facilities and safety valves causing operational problems, production deficiencies and enormous economic losses. This work aims to study the effect of series of synthesized aryl ionic liquids (ILs) containing different alkyl chains, named as R8-IL, R10-IL, R12-IL, and R14-IL, on the onset precipitation point of asphaltene in crude oil. R8-IL, R10-IL, R12-IL, and R14-IL were synthesized with high yields (the yield varied between 82 and 88%) and characterized via different tools of analysis (FTIR, 1H NMR, and Elemental Analysis). Their Thermal Gravimetric Analysis (TGA) was investigated and showed a reasonable degree of stability. It was found that R8-IL (short alkyl chain) has the highest stability, while R14-IL (long alkyl chain) is the lowest one. Quantum chemical calculations were conducted to study the reactivity and geometry of their electronic structures. Moreover, surface and interfacial tension of them were studied. It was found that the efficiency of the surface active parameters increased by increasing the length of the alkyl chain. The ILs were evaluated to delay the onset precipitation point of asphaltene using to different methods; the kinematic viscosity and the refractive index. Results from the two methods showed delaying of onset precipitation after the addition of the prepared ILs. The asphaltene aggregates was dispersed due to the π–π* interactions and hydrogen bonds formation with the ILs.

Synthesis and Surface Properties of Piperidinium-Based Herbicidal Ionic Liquids as a Potential Tool for Weed Control

A series of piperidinium-based herbicidal ionic liquids (HILs) were synthesized and investigated. The designed HILs, obtained with high yields, consisted of cation 1-alkyl-1-methylpiperidinium with surface activity and a commercially available herbicidal anion: (3,6-dichloro-2-methoxy)benzoates (dicamba). The above-mentioned compounds were characterized in terms of surface activity and phytotoxicity. Preliminary results were obtained at higher wettability for all HILs when compared to the wettability of commercial Dicash, with HIL having 18 atoms in the carbon chain being the best effectiveness in wetting surfaces (weeds and crop leaves), whereby a drop of HILs with short alkyl chains (C8-C10) could not slide down a leaf. Our findings present that wettability or mobility of HILs drops varied depending on the plant species. Moreover, in this study, by zeta potential and atomic force microscopy measurements, we provide conclusive evidence to demonstrate that alkyl chain elongation plays a significant role in the evolution of surface properties of HILs.

Linking Molecular Structure and Lubrication Mechanisms in Tetraalkylammonium Orthoborate Ionic Liquids

While ionic liquids (ILs) have gained wide interest as potential alternative lubricants able to meet the requirements of next-generation tribological systems owing to their unique physico-chemical properties and promising lubricating behavior, our understanding of the mechanisms by which ILs reduce friction and/or wear is still elusive. Here, we combine macroscale tribological experiments with surface-analytical measurements to shed light on the lubrication mechanisms of a class of halogen-free ILs, namely tetraalkylammonium orthoborate ILs, at steel/steel sliding contacts. The tribological results indicate an improvement of the friction-reducing properties of these ILs as the length of the alkyl chains attached to ammonium cations increases. X-ray photoelectron spectroscopy analyses provide further evidence for the dependence of the lubrication mechanism of tetraalkylammonium orthoborate ILs on the IL structure. In the case of tetraalkylammonium orthoborate ILs with asymmetric ammonium cations containing a long alkyl chain, no sacrificial tribofilms were formed on steel surfaces, thus suggesting that the friction-reducing ability of these ILs originates from their propensity to undergo a pressure-induced morphological change at the sliding interface that leads to the generation of a lubricious, solid-like layered structure. Conversely, the higher friction response observed in tribological tests performed with tetraalkylammonium orthoborate ILs containing more symmetric ammonium cations and short alkyl chains is proposed to be due to the inability of this IL to create a transient interfacial layer owing to the reduced van der Waals interactions between the cationic alkyl chains. The resulting hard/hard contact between the sliding surfaces is proposed to lead to the cleavage of boron-oxygen bonds in the presence of water to form species that then adsorb onto the steel surface, including trivalent borate esters and oxalic acid from the decomposition of orthoborate anions, as well as tertiary amines from the degradation of alkylammonium cations induced by hydroxides released during the orthoborate decomposition reaction. The results of this work not only establish links between the molecular structure of a class of halogen-free ILs, their lubricating performance, and lubrication mechanism, but also provide evidence for the existence of multiple mechanisms underpinning the promising lubricating properties of ILs in general.

The Nanostructure of Alkyl-Sulfonate Ionic Liquids: Two 1-Alkyl-3-methylimidazolium Alkyl-Sulfonate Homologous Series.

The functionalization of polymers with sulfonate groups has many important uses, ranging from biomedical applications to detergency properties used in oil-recovery processes. In this work, several ionic liquids (ILs) combining 1-alkyl-3-methylimidazolium cations [CnC1im]+ (4 ≤ n ≤ 8) with alkyl-sulfonate anions [CmSO3]- (4 ≤ m ≤ 8) have been studied using molecular dynamics simulations, totalizing nine ionic liquids belonging to two homologous series. The radial distribution functions, structure factors, aggregation analyses, and spatial distribution functions reveal that the increase in aliphatic chain length induces no significant change in the structure of the polar network of the ILs. However, for imidazolium cations and sulfonate anions with shorter alkyl chains, the nonpolar organization is conditioned by the forces acting on the polar domains, namely, electrostatic interactions and hydrogen bonding.

Effect of bulky anions on the liquid-liquid phase transition in phosphonium ionic liquids: Ambient and high-pressure dielectric studies

Although the first-order liquid–liquid phase transition (LLT) has been reported to exist in various systems (i.e., phosphorus, silicon, water, triphenyl phosphite, etc.), it is still one of the most challenging problems in the field of physical science. Recently, we found that this phenomenon occurs in the family of trihexyl(tetradecyl)phosphonium [P666,14]+ based ionic liquids (ILs) with different anions (Wojnarowska et al in Nat Commun 13:1342, 2022). To understand the molecular structure–property relationships governing LLT, herein, we examine ion dynamics of two other quaternary phosphonium ILs containing long alkyl chains in cation and anion. We found that IL with the anion containing branched –O–(CH2)5–CH3 side chains does not reveal any signs of LLT, while IL with shorter alkyl chains in the anion brings a hidden LLT, i.e., it overlaps with the liquid-glass transition. Ambient pressure dielectric and viscosity measurements revealed a peculiar behavior of ion dynamics near Tg for IL with hidden LLT. Moreover, high-pressure studies have shown that IL with hidden LLT has relatively strong pressure sensitivity compared to the one without first-order phase transition. At the same time, the former exposes the inflection point indicating the concave-convex character of logτσ(P) dependences.