Increasing Alkyl Chain Length Research Articles

Magnetic Microemulsions Stabilized by Alkyltrimethylammonium-Based Magnetic Ionic Liquids Surfactants (MILSs)

While traditional microemulsions are versatile media for nanoscience and nanotechnology, stimulus-responsive microemulsions are more challenging to realize, and only a handful of cases have been reported. We here introduce magnetic microemulsions (MMEs) stabilized by alkyltrimethylammonium-based magnetic ionic liquids surfactants (MILSs), paired with water as the polar phase, aliphatic oils as the nonpolar phase, and aliphatic alcohols as the cosurfactant. n-Hexane coupled with n(MILSs/1-butanol) = 1:4 showed the most excellent ability to form MMEs, and the range of the monophasic region was expanded with increasing alkyl chain length of MILSs cation. Classical oil-in-water (O/W), bicontinuous (BC) sponge structure, and inverse water-in-oil (W/O) subregions were clarified by conductivity method. Dynamic light scattering showed that the diameter of W/O microemulsions droplets were about 2-6 nm. Magnetic susceptibility and rheological measurements revealed that these MMEs are with high magnetic susceptibility and low viscosity, which show interesting potential applications based on a manipulation via external magnetic field. Moreover, these MMEs showed Newtonian-like flow behavior within respective subregions, and their magnetic susceptibility was not affected by the subregion structure but MILSs mass fraction.

Short Chain (≤C4) Esterification Increases Bioavailability of Rosmarinic Acid and Its Potency to Inhibit Vascular Smooth Muscle Cell Proliferation

Rosmarinic acid is a natural phenolic acid and active compound found in many culinary plants, such as rosemary, mint, basil and perilla. Aiming to improve the pharmacokinetic profile of rosmarinic acid and its activity on vascular smooth muscle cell proliferation, we generated a series of rosmarinic acid esters with increasing alkyl chain length ranging from C1 to C12. UHPLC-MS/MS analysis of rat blood samples revealed the highest increase in bioavailability of rosmarinic acid, up to 10.52%, after oral administration of its butyl ester, compared to only 1.57% after rosmarinic acid had been administered in its original form. When added to vascular smooth muscle cells in vitro, all rosmarinic acid esters were taken up, remained esterified and inhibited vascular smooth muscle cell proliferation with IC50 values declining as the length of alkyl chains increased up to C4, with an IC50 of 2.84 µM for rosmarinic acid butyl ester, as evident in a resazurin assay. Vascular smooth muscle cells were arrested in the G0/G1 phase of the cell cycle and the retinoblastoma protein phosphorylation was blocked. Esterification with longer alkyl chains did not improve absorption and resulted in cytotoxicity in in vitro settings. In this study, we proved that esterification with proper length of alkyl chains (C1–C4) is a promising way to improve in vivo bioavailability of rosmarinic acid in rats and in vitro biological activity in rat vascular smooth muscle cells.

Impact of alkyl chain length of temperature-responsive ionic liquids on the aggregation behavior in ionic liquid microemulsions

As is known to all, the alkyl chain is a perfect tool to regulate the microstructure of ionic liquid(IL) microemulsion directly. However, it is still a great challenge to design a new type of temperature-responsive IL with different alkyl chain length to construct the stimulus microemulsion. In this study, a new class of temperature-responsive IL microemulsions was built for the first time, which is composed by [P444,n]Br (n = 8,10,12,14,16,18), [C12mim]Br and H2O. The phase diagram and dynamic light scattering analysis revealed that the size of IL microemulsion droplets can be effective regulated by the alkyl chain length of temperature-responsive IL, so as to gain a series of organized structures. The molecular dynamic(MD) simulations were performed by a series of [P444,n]Br/[C12mim]Br/H2O mixture systems to illustrate this unique aggregation behavior of droplet. Simulation results are presented and discussed via the data of interaction energies, aggregation numbers, radial distribution functions (RDFs) and coordination numbers. The results indicate that the aggregation sizes of [C12mim]+ become smaller with the increase of alkyl chain length of tetrabutylphosphonium cation, which agrees well with experimental results. This is because that the weakened interaction of temperature-responsive IL and water molecules by the long alkyl chain could reduce the electrostatic repulsion of the polarity groups of the surfactants, which may decrease the size of the aggregate. These finding can help in further understanding the structure variation law of temperature-responsive IL microemulsions and thereby improve microemulsion theory.

Impact of aliphatic acyl and aromatic thioamide substituents on the anticancer activity of Ru(II)-p-cymene complexes with acylthiourea ligands-in vitro and in vivo studies.

Six different acylthiourea ligands (L1-L6) and their corresponding Ru(II)-p-cymene complexes (P1-P6) were designed to explore the structure-activity relationship of the complexes upon aliphatic chain and aromatic conjugation on the C- and N-terminals, respectively. The compounds were synthesized and adequately characterized using various analytical and spectroscopic techniques. The structures of P2-P6, solved using single crystal X-ray diffraction (XRD), confirmed the neutral monodentate coordination of the S atoms of the acylthiourea ligands to Ru(II) ions. In silico studies showed an increase of lipophilicity for the ligands with an increase in alkyl chain length or aromatic conjugation at the C- or N-terminal, respectively. Subsequently, mitogen-activated protein kinases (MAPK) were predicted as one of the primary targets for the complexes, which showed good binding affinity towards extracellular signal-regulated kinases (ERK1, ERK2 and ERK5), c-Jun N-terminal kinase (JNK) and p38 of the MAPK pathway. Henceforth, the complexes were tested for their anticancer activity in lung carcinoma (A549) and cisplatin-resistant lung carcinoma (cisA549R) cells and human umbilical vein epithelial normal cells (HUVEC). Interestingly, an increase in chain length or aromatic conjugation led to an increase in the activity of the complexes, with P5 (7.73 and 13.04 μM) and P6 (6.52 and 14.45 μM) showing the highest activity in A549 and cisA549R cells, which is better than the positive control, cisplatin (8.72 and 44.28 μM). Remarkably, we report the highest activity yet observed for complexes of the type [(η6-p-cymene)RuIICl2(S-acylthiourea)] in the tested cell lines. Aqueous solution studies showed that complexes P5 and P6 are rapidly hydrolyzed to produce solely aquated species that remained stable for 24 h. Staining assays and flow cytometric analyses of P5 and P6 in A549 cells revealed that the complexes induced apoptosis and arrested the cell cycle predominantly in the S phase. In vivo studies demonstrated the higher toxicity of cisplatin and a comparatively higher survival rate of mice injected with the most active complex P6. Histological analyses revealed that treatment with P6 at high doses of up to 8 mg kg-1 did not cause any palpable damage to the tested organs.

Assessment of the Relationship between Degradation and Emission Activities of Carbon Capture Amines Based on their Chemical Structures

In this work, 16 alkanolamines were investigated to determine the effect of their chemical structural positioning of different functional groups on the rates of amine degradation and ammonia (NH3) emissions as well as to determine if there were inter-relationships between degradation and emission based on their structures. The oxidative degradation and emission experiments were carried out continuously for 2 weeks at the temperature of 60 C using 99.5% O2 gas set at a flow rate of 200±2 mL/min. The amine degradation rate was determined by evaluating the rate of decrease of the amine concentration with time. The NH3 emissions was investigated by collecting the NH3 released from the amine solution in an impinger system set up in accordance with the relevant EPA method. The effect of the alkyl chain length in between amino and hydroxyl groups was investigated by considering groups of primary and tertiary alkanolamines. The degradation rate was observed to decrease with increasing alkyl chain length which helped to strengthen the N-C bond due to the electron donating properties of the alkyl group. The degradation rate was found to decrease in the order: MEA  3A1P > 5A1P and DMAE > 3DMA1P > 4DMA1B for primary and tertiary alkanolamines, respectively. In contrast however, the opposite trend was observed for NH3 emissions in the two amine groups. In the case of end alkyl chain length of secondary alkyl-alkanolamines, it was observed that a longer chain length led to a decrease in the degradation and NH3 emission rates. Their order was: MAE  EAE > BAE. The longer chain length of end alkyl group contributed to both electronic and steric hindrance effects that increase the stability of N-C bond which reduced the formation free radicals thereby decreasing the degradation and NH3 emission rates. For tertiary alkyl-alkanolamines, the degradation rate noticeably decreased in the order of MDEA > EDEA > BDEA. The reasons are similar to those previously given for the same group in secondary alkyl-alkanolamine. NH3 emission rates obtained by this amine group was extremely low with the actual trend unable to be clearly determined. The presence of hydroxyl group known as an electron withdrawing group enhanced the degradation rate as a result its ability to weaken the N-C bond. This facilitated the occurrence of amine degradation. This trend was obtained for secondary alkanolamines (less steric effect) whose degradation and NH3 emission rates of DEA containing two hydroxyl groups were higher than those for EAE containing one hydroxyl group. Steric hindrance effect derived from the presence of the hydroxyl group was also there specifically for tertiary alkanolamines and sterically hindered primary amines comparisons. Having more hydroxyl group in the amine molecule will enhance the oxidative degradation reaction, but at the same time, will promote the steric hindrance effect. The latter effect is more dominant, and thus, increased hydroxyl group number has the net effect of obstructing the occurrence of oxidative degradation reaction thereby resulting in the decrease of the degradation rate. On the other hand, we did not observe any significant difference in NH3 emission rate from tertiary and sterically hindered primary amines due to slow rate of degradation as a result of the steric effect introduced by their structure. Since the net degradation rate decreased with increasing number of hydroxyl groups, it can be concluded that the steric hindrance effect is more dominant in the rate of amine degradation and NH3 emission than the electronic effect.

Theoretical study of intermolecular interactions in protic ionic liquids: a single ion pair picture

Protic ionic liquids are made via intermolecular transfer between cation and anion. This research employs theoretical calculation to gain understanding of the intermolecular interactions at single-ion-pair level and their consequences to the macroscopic properties of the ionic liquids. The protic ionic liquids used in this study are ethylammonium nitrate (EAN), propylammonium nitrate (PAN), and butylammonium nitrate (BAN). Molecular structures of ions and ion pair of each liquid are optimized using the density functional theory. The ion pair binding energies and infrared spectra of optimized structures are investigated. Infrared spectra of separated cation and anion are compared with cation-anion ion pair to specify the vibrational band shifts due to intermolecular interactions. The infrared-spectra show the hydrogen-bond stretching modes in the far-infrared region at the wavenumber between 108-252 cm−1 and the red shifts of four vibrational bands due to intermolecular interactions between the ions. Three vibrational band shifts are mainly due to Coulomb force, and the other shift is caused by combination of intermolecular interactions. Moreover, the energy calculations show that the binding energy decreases as the alkyl chain length increases.

Effect of Anionic Amphiphiles on the Morphology of Hexagonal Plate-like ZnO Particles.

Zinc oxide (ZnO) particles were synthesized in the presence of anionic surfactants (ASs). The effect of ASs on the morphology of the ZnO particles was investigated by using ASs with various alkyl chain lengths and changing the molar ratio of AS/ZnSO4. Hexagonal plate-like ZnO particles were formed in the presence of ASs. Adsorption of the AS on the c face of the ZnO crystals inhibited (promoted) crystal growth along the c-axis (ab-axis) direction. Increasing the molar ratio of AS/ZnSO4 decreased the particle thickness, owing to the resulting increase in the coverage of the c face with AS. The particle diameter of the hexagonal plate-like ZnO particles (the diagonal length of the hexagonal plate) increased with increasing alkyl chain length of AS as a result of the van der Waals interactions between the alkyl chains. The data indicate that the particle diameter and thickness can be controlled by fine-tuning the van der Waals interactions between the alkyl chains and the coverage of the c face of the ZnO particles with AS.

Effect of Alkyl Chain Length of Acylated α‐Cyclodextrin‐Threaded Polyrotaxanes on Thermoresponsive Phase Transition Behavior

AbstractThe temperature‐dependent phase transition behavior of acetylated polyrotaxanes (PRXs) consisting of acylated α‐cyclodextrins threaded onto a poly(ethylene glycol) chain in an aqueous solution is investigated. Acetyl (Ac), propionyl (Pr), and butyryl (Bu) group‐modified PRXs with different degrees of substitution are synthesized to elucidate the effect of the alkyl chain length of the acyl groups on temperature responsivity. Ac‐PRXs, Pr‐PRXs, and Bu‐PRXs are dissolved in water and exhibit temperature‐dependent transmittance changes accompanied by coacervate formation. However, the temperature responsivity of acylated PRXs is seen in limited degree of substitution range (≈10%). The maximum degree of substitution to show temperature responsivity of acylated PRXs decreases with increasing alkyl chain length of the acyl groups. Transmittance measurements of acylated PRXs in the presence of urea reveal that the alkyl chain length of the acyl groups determines the predominant force involved in the temperature‐induced phase transition. During the temperature‐induced phase transition of Pr‐PRXs and Bu‐PRXs, hydrophobic interactions are predominant; however, hydrogen bond formation may occur in Ac‐PRXs. These fundamental findings related to acylated PRXs will facilitate the application of PRXs as thermoresponsive supramolecular materials.

Proton transfer reaction mass spectrometry investigations of phthalate esters via direct headspace sampling

One of the most common environmentally relevant groups of pollutants are phthalate esters. After decades of industrial use, they have become ubiquitous in the environment and analytical methods to chemically detect them in trace amounts are required. In this study, details of Proton Transfer Reaction-Mass Spectrometry (PTR-MS) investigations for the reactions of phthalic acid and ten phthalate esters with H3O+ as a function of the reduced electric field are presented. A characteristic product ion observed for several of the phthalate esters is protonated phthalic anhydride (m/z 149.02, C8H5O3+). However, not all of the phthalates investigated in this study fragment to produce this product ion following proton transfer. For alkyl diester phthalates, loss of the corresponding alcohol results in the main product ion, but its abundance decreases with increasing alkyl chain length, whilst in comparison for the dialkyl ester phthalates, the protonated phthalic anhydride ion abundance increases with increasing alkyl chain length and with increasing reduced electric field. Collisional induced dissociation in the drift tube of the PTR-MS is shown to be useful as means to manipulate the underlying ion chemistry, leading to unique product ions distinctive to phthalates. The results reported in this work represent a wealth of new data that will be of use for developing a PTR-MS analytical method for the quick, selective and reliable identification of phthalates in the environment.

Understanding the Enhanced Methanol Oxidation Reactivity on Sulfur-Organic Compound Decorated Pt Electrode in Alkaline Media

Due to the rapid increase in environmental and energy issues, it is required to replace fossil fuel-driven conventional internal combustion engines with an energy conversion system using sustainable fuels. Although fuel cell is one of the possible candidates due to its high efficiency, the storage and transportation of hydrogen fuel hinder its widespread use.1 To overcome this problem, hydrogen careers, hydrogen-rich liquid and solid-phase materials, have been proposed as alternative fuels for fuel cell systems. Among the hydrogen carriers, methanol is one of the promising candidates due to its low production cost and high energy density. However, the slow kinetics of the methanol oxidation reaction (MOR), which proceeds via a complex six-electron pathway, limits the overall efficiency of the direct methanol fuel cell (DMFC).2 Much effort has been put into improving the MOR activity, including the development of electrocatalyst by metal alloying and surface modification of the electrocatalyst by thiol derivatives.3 Here, we focused on using sulfur-organic compound copolymer synthesized from S8 and organic molecules as a surface modifier. We then explored the reaction mechanisms on Pt surface in the alkaline environment by tracking the surface-bound intermediates using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS). We selected styrene as an organic component and synthesized sulfur-organic compound copolymer (poly(s-st)). Synthesized poly(s-st) was decorated on the Pt surface by simply immersing the electrode into the poly(s-st)-contained solution. Cyclic voltammogram and X-ray photoelectron spectroscopy confirm the surface modification of the Pt surface by poly(s-st), which was stable after 5 cycles of potential cycling in 0.1 M KOH electrolyte. The oxidation current at 0.78 V vs. RHE, which is related to the MOR, was more significant than the pristine Pt electrode, which confirms the improvement of the MOR activity by poly(s-st) modification. The degree of activity enhancement became more substantial with the increase in alkyl chain length of alcohol fuels (methanol < propanol < 1-butanol), suggesting the reason of the enhanced activity to be the hydrophobic interaction between phenyl group of a surface modifier and alkyl portion of alcohol fuels which could facilitate the fuel supply on Pt electrode. In order to support our hypothesis, we performed SEIRAS measurement, where we observed a peak corresponds to the site-blocking species at ca. 1500 cm-1 for pristine Pt surface, while no corresponding peak was observed for poly(s-st) modified Pt surface. We will discuss the changes in the surface reaction mechanism based on the direct observation of the reaction intermediates by SEIRAS. It will also be demonstrated that the holistic information about the nature of the adsorbed species can provide a strategy to design the surface modifier to tune the energetics of key reaction intermediates, leading to further improvements in electrocatalytic activity for the methanol oxidation reaction.[1] Z-F. Li et al. Electrochim. Acta. 2017, 228, 351–360.[2] C. Lamy et al. J Appl. Electrochem. 2001, 31, 799–809.[3] H. Zimmermann et al. Chem. Eur. J. 2000, 4, 592–599.

Synergistic interactions of ionic liquids and antimicrobials improve drug efficacy.

SummaryCombinations of ionic liquids (ILs) with antimicrobial compounds have been shown to produce synergistic activities in model liposomes. In this study, imidazolium chloride-based ILs with alkyl tail length variations are combined with commercially available, small-molecule antimicrobials to examine the potential for combinatorial and synergistic antimicrobial effects on P. aeruginosa, E. coli, S. aureus, and S. cerevisiae. The effects of these treatments in a human cell culture model indicate the cytotoxic limits of ILs paired with antimicrobials. The analysis of these ILs demonstrates that the length of the alkyl chain on the IL molecule is proportional to both antimicrobial activity and cytotoxicity. Moreover, the ILs which exhibit synergy with small-molecule antibiotics appear to be acting in a membrane permeabilizing manner. Collectively, results from these experiments demonstrate an increase in antimicrobial efficacy with specific IL + antimicrobial combinations on microbial cultures while maintaining low cytotoxicity in a mammalian cell culture model.

Synthesis and Determination of Critical Micelle Concentration of Betainthioates Surfactants

AbstractTwo series of monotailed and bolaphiles surfactants having quaternary ammonium bromide polar head have been synthesized and characterized. The critical micelle concentration (CMC) of the synthesized cationic surfactants was determined by conductimetric method. According to CMC values, the increase in alkyl chain length leads to a decrease in CMC and the bola‐type exhibits a higher CMC than their counterpart's monotailed.

Bioinspired surfaces with strong water adhesion from electrodeposited poly(thieno[3,4-b]thiophene) with various branched alkyl chains

In this original work, we wanted to prepare surfaces with both high hydrophobicity and strong water adhesion, as observed on rose petals or gecko foot. The surfaces are prepared by electropolymerization and using thieno[3,4-b]thiophene monomers with various branched alkyl chains. Here, branched alkyl chains are used to their lower hydrophobic properties compared to linear alkyl chains and fluorinated chains. It is observed a change from structured to smooth when the branched alkyl chain length increases. Using short branched alkyl chains, the surfaces are mainly composed of wrinkles and nanoparticles displaying high hydrophobicity ( $${\theta }_{\mathrm{w}}$$ up to 134.9°) combined with strong water adhesion, as observed on rose petals even if $${\theta }_{\mathrm{w}}$$ is less important. Dynamic contact angle measurements show that their water adhesion is extremely strong and water droplets remain stuck on them. By adding H2O in the solvent (CH2Cl2 + H2O), it is possible to release gas bubbles (H2 and/or O2) in-situ leading to more porous surfaces but here it is observed an increase of surface hydrophilicity. These original polymer surfaces have potential applications in water harvesting systems or oil/water separation membranes, for example.

Synthetic Bilayers on Mica from Self-Assembly of Hydrogen-Bonded Triazines.

This study describes organic thin films prepared under a range of conditions from a model series of bis-N-alkyl chloro-triazines functionalized with short alkyl chains from ethyl to hexyl. The pure films were characterized using atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). When cast on mica, these compounds assemble as crystalline sheets made up of a synthetic bilayer along the crystallographic ab-plane with an internal hydrogen-bonded domain between external alkyl chains. These micron-scale surfaces stack along the c-axis, and increasing the alkyl chain length results in changes to the crystal morphology from needles to nanoscale plates. Thicker films produce nanoscale, pyramidal stacks of bilayers. Compared to atomically flat mica, a rougher, unetched silicon substrate produced irregular domains in the secondary bilayer. Films of mixtures comprising the ethyl derivative with butyl, pentyl, or hexyl derivative were imaged using time-of-flight secondary-ion mass spectrometry (ToF-SIMS) that indicated a trend toward a constant stoichiometry with increasing alkyl chain length. AFM of mixed films on mica showed single bilayers of height <2 nm, with an acceptable correlation to the XRD measurements, supporting a constant stoichiometry. These materials permit easy modification of mica to a micron-scale, atomically flat hydrophobic surface, and the use of mixtures with different alkyl chain lengths suggests a method to improve the quality of functional organic thin films.

Effect of imidazolium's ionic liquids with different anions and alkyl chain length on phytotoxicity and biochemical analysis of maize seedling

The structural moieties of ionic liquids (IL), as well as water miscibility nature, render it toxic in the various biological system. The ecotoxicity of animals and microbes are well established for ionic liquids. Albeit, the phytotoxicity of ILs have not been explored exclusively. Therefore, the effect of three imidazolium-based ILs, namely, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-octyl-3-methylimidazolium chloride ([Omim]Cl), and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) on performance and biochemical constituents of maize seedling were studied. ILs in different concentrations ranging from 50 mg/L to 350 mg/L were applied to maize seeds continuously for 7 days under in vitro condition. The experimental results showed that ILs in high concentrations (250 and 350 mg/L) harm seed germination and seedling growth of maize, following the order: [Bmim]BF4 > [Omim]Cl > [Bmim]Cl. ILs treatment caused a reduction in seed germination, weight of root and shoot, leaf area, relative water content, photosynthetic pigments production. The antioxidant activity of maize seedling was decreased when the concentration of ILs was increased, thus in ILs stressed condition, the free radical could not be effectively scavenged. However, an increase in the phenolic content was observed when ILs concentration increased from 50 mg/L to 350 mg/L. It has been observed that increasing alkyl chain length attached to imidazolium cation of ILs from butyl to octyl harm the performance of maize seedling. Moreover, IL having BF4 anion is more toxic than ILs having Cl anion on maize growth seedling.

Investigation of the Effect of Alkyl Chain Length on Molecular Interactions Between Methyl Benzoate with Alcohols: A Study of Physicochemical Properties

Densities, speeds of sound, and viscosities of binary mixtures of methyl benzoate (MB) with ethanol, 1-propanol, and 1-butanol were measured at temperature ranging from T = 293.2 to 313.2 K and refractive indices were determined at T = 303.2 K. Excess molar volumes, VE, isentropic compressibility deviations ∆κs and viscosity deviations, Δη, were obtained and fitted with the Redlich–Kister equation with satisfactory results. Based on the measured and derived physicochemical properties, the influence of the alkyl chain length of the alcohol on the molecular interactions of the studied mixtures was explored. The results show that both hydrogen bond interaction between carbonyl group of MB and hydroxyl group of alcohol and the packing efficiency, such as accommodation of alcohol in the interstice of MB, play an important role in the microstructure of the mixtures, which leads to the disruption of alcohol with the addition of MB. Moreover, by comparing VE, ∆κs and Δη values of MB (1) + alcohol (2) systems at T = 303.2 K, it is found that the strength of hydrogen bond interaction and the packing efficiency significantly weakens with increasing alkyl chain length of alcohol in going from ethanol to 1-butanol, resulting in the VE values of the studied systems gradually changing from a negative deviation to an S shape, the ∆κs and Δη values have negative deviations, and the ∆nD values have positive deviations. The obtained results will provide thermodynamic guidance for the industrial purification of methyl benzoate.

Effect of triglyceride on the microstructure and gas permeation performance of Pebax-based blend membranes

A series of Pebax 2533/triglyceride (20 wt%) blend membranes were prepared to study the influence of triglyceride structure on Pebax-based membrane for the first time. The microstructure and morphology of blend membranes were characterized by XRD and SEM. The interaction and compatibility between Pebax and triglyceride were characterized by ATR-FTIR and DSC. The mechanical property of Pebax/triglyceride blend membrane was tested by universal testing machine. The thermal stability and the triglyceride content in blend membranes were characterized by TGA. Pebax showed relatively high compatibility with tripropionin (TPP), tributyrin (TBT) and tricapronin (TCP) and Pebax/triglyceride blend membranes showed reasonable mechanical property. The thermal stability of the Pebax/triglyceride blend membranes increased with the increase of triglyceride alkyl chain and Pebax/TCP blend membrane showed the highest thermal stability. For gas permeation of Pebax/triglyceride blend membranes, it relied on the combined action of ester group concentration, plasticization of triglyceride and volume resistance of alkyl chain. CO2 permeability of Pebax/triglyceride blend membranes all increased in comparison with Pebax membrane. However, due to the decline of ester group concentration and the increase of volume resistance with the increase of triglyceride alkyl chain length, the degree of CO2 permeability enhancement of blend membranes decreased, that was Pebax/TPP > Pebax/TBT > Pebax/TCP. More specifically, for Pebax/triglyceride blend membranes, diffusion coefficients were the major factors contributing to the improvement of CO2 permeability. While solubility coefficients were the major factors to determine the trend of CO2 permeability. Thus, Pebax/TPP blend membrane showed the highest CO2 permeability of 566 Barrer with moderate CO2/N2 selectivity of 25 at 35 °C. While Pebax/TCP blend membrane showed constant CO2 permeability around 508 Barrer within 120 h gas permeation testing.

Structural effects on thermodynamic behavior and hydrogen bond interactions of water–ionic liquid systems

The relationships between the structure and the thermodynamic behavior and the hydrogen bond (HB) interactions in H2O + ionic liquid (IL) systems were systematically investigated for the first time. Imidazolium-based ILs comprising 1-alkyl-3-methylimidazolium cations ([RMIM]+) and various anions such as acetate ([AC]-), thiocyanate ([SCN]-), tetrafluoroborate ([BF4]-), and bis(trifluoromethylsulfonyl)imide ([Tf2N]-) were investigated. The vapor–liquid equilibrium (VLE) of H2O + IL systems was experimentally determined and predicted by the UNIFAC-Lei model. The results demonstrated that the vapor pressure is mainly dependent on the type of anion and increases slightly with an increase in the cation alkyl chain length. Quantum chemistry calculation and wavefunction analysis clearly revealed the relationship between the VLE and the HB interactions. This study provides theoretical guidance for designing and screening task-specific ILs for chemical processes such as gas dehydration and dehumidification.

Effect of cation alkyl chain length on photo-luminescence dynamics of ionic liquids containing dicyanoaurate(I) anion

Viscosity and photo-luminescence dynamics of N-alkyl-N-methylpyrrolidinium dicyanoaurate (I) ([Py1n][Au(CN)2]) (n = 4, 6, 8, and 12) and 1-alkyl-3-methylimidazolium dicyanoaurate (I) ([Cnmim][Au(CN)2]) (n = 4, 8, and 12) were studied. The viscosity increased with increasing alkyl chain length for both cations, and the temperature dependence of the viscosity showed a good fit with the Vogel–Fulcher–Tammann equation. Steady-state luminescence of both [Py1n][Au(CN)2] and [Cnmim][Au(CN)2] showed dual luminescent bands at around 370 nm and 460 nm. The band with the shorter wavelength most likely arose owing to fluorescence of the trimer of the anion, and the longer-wavelength band could be assigned to phosphorescence of the linear oligomers of the anion. The relative ratio of the intensity of the fluorescence to that of the phosphorescence of [Py1n][Au(CN)2] was significantly smaller than that of [Cnmim][Au(CN)2]. The luminescent dynamics measured by a streak camera revealed a short lifetime of fluorescence, and the phosphorescence peak shift with time. The phosphorescence peak shift was attributed to two contributions from the amplitudes and the time constants. Based on the dependence on the solvent viscosity and the anion concentration, the slower time constant was assigned to the dynamics of tetramer formation owing to a reaction between the trimer and the monomer. The faster dynamics were assigned to the solvation dynamics, which were accompanied by the structural change of the trimer after intersystem crossing.

Study of the toluene absorption capacity and mechanism of ionic liquids using COSMO-RS prediction and experimental verification

As green solvents, ionic liquids (ILs) are quite suitable for the absorption of volatile organic compounds (VOCs) such as benzene and its homologues. However, solvent selection is the key to the VOC absorption process. In the present study, a rapid solvent screening tool, Conductor-like Screening Model for Real Solvents (COSMO-RS), was used to predict the solubility of toluene in 816 ILs. The effects of four structure characters, namely, the type and alkyl chain length of the cations and anions on the solubility of toluene were discussed. The following conclusions were drawn from the results: (1) ILs with pyrrolidinium-based cations showed better solubility than pyridinium- and imidazolium-based ones. (2) The solubility of toluene in PF6-based ILs increased with the increasing alkyl chain length, while its solubility in Ac-based ILs exhibited the opposite trend. (3) Toluene showed greater solubility in Cl-based ILs than those based on other anions. (4) The solubility of toluene increased with the anion alkyl chain length. Ac-based ILs were chosen as the most promising potential solvents, and further studied to determine the relationship between various interaction energy parameters and toluene solubility. The results showed that the misfit energy played a dominant role during the absorption process. Furthermore, several ILs were selected for experimental verification of the predicted solubility behavior using liquid and gaseous toluene. The results demonstrated that COSMO-RS could be used to semi-quantitatively and qualitatively predict the solubility of toluene, and this model had promising prospects in screening ILs for VOCs absorption. In summary, this study provided a fundamental basis and practical data for the control and treatment of VOCs.