Study on the Polarity of bmimPF6/Tween80/toluene Microemulsion Characterized by UV-Visible Spectroscopy

With the aid of nonionic surfactant Tween80, the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆) forms nonaqueous microemulsions with toluene. The phase diagram of the ternary system was prepared at 25°C. It was demonstrated that there were a single-phase region and a two-phase region in the ternary phase diagram. The single-phase region could be further divided into toluene-in-bmimPF₆, bicontinuous and bmimPF₆-in-toluene microemulsion regions by electrical conductivity. And by the use of methyl orange as an absorption probe, the polarity of the bmimPF₆-in-toluene microemulsion was probed by UV-vis spectroscopy. A relatively constant polarity of the microemulsion droplets is obtained in the bmimPF₆ microemulsion.     

Surfactant-free Ionic Liquid Microemulsions of N,N-dimethylformamide, 1-butyl-3-methylimidazolium hexafluorophosphate,and toluene

The phase diagram of a ternary system consisting of the hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆), N, N-dimethylformamide (DMF), and toluene was prepared at 25°C. A single-phase microemulsion and a multiphase region were demonstrated. The systems were nonaqueous IL microemulsions in the absence of traditional surfactants. The single-phase region could be divided into toluene-in-bmimPF₆, bicontinuous, and bmimPF₆-in-toluene subregions by electrical conductivity, similar to the case of surfactant-based IL microemulsions. And by the use of methyl orange as an absorption probe, the polarity of the bmimPF₆-in-toluene microemulsion was probed by UV–vis spectroscopy. The polarity of bmimPF₆ domains increased with increasing bmimPF₆ constant, and a relatively constant polarity was obtained when bmimPF₆ was increased to a certain extent.     

TX-100/water/1-butyl-3-methylimidazolium hexafluorophosphate microemulsions

Both ionic liquids and water are typical green solvents. In this work, the phase behavior of the ternary system consisting of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), TX-100, and water was determined at 25.0 degrees C. The water-in-bmimPF6, bicontinuous, and bmimPF6-in-water microregions of the microemulsions were identified by cyclic voltammetry method using potassium ferrocyanide K4Fe(CN)6 as the electroactive probe. Dynamic light scattering (DLS) and the UV-vis method were used to characterize the microemulsions. It was demonstrated that the hydrodynamic diameter (Dh) of the bmimPF6-in-water microemulsions is nearly independent of the water content but increases with increasing bmimPF6 content due to the swelling of the micelles by the ionic liquid. The UV-vis further confirmed the existence of water domains in the water-in-bmimPF6 microemulsions, and the salt potassium ferricyanide K3Fe(CN)6 could be dissolved in the water domains.     

Effect of polyethylene glycol (PEG-400) on the 1-butyl-3-methylimidazolium tetrafluoroborate-in-cyclohexane ionic liquid microemulsion

The effect of a common polymer, polyethylene glycol with molecular weight of 400 (PEG-400) on the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄)/Triton X-100/cyclohexane ionic liquid (IL) reverse microemulsion has been investigated. The addition of PEG-400 leaded to the linear increase of the microemulsion droplet size, in accordance with the observation of dispersed phase, showing that PEG-400 was only solubilized into the polar interior of the IL microemulsions. FTIR spectroscopic analysis indicated that the addition of PEG-400 decreased the electrostatic interaction between the oxygen atoms of OE units and the positive electrical charged imidazolium cation of bmimBF₄. At the same time, the oxygen atoms of PEG-400 can also interact with the imidazolium cation. These results suggested that small amounts of PEG-400 entered the palisade layers of the IL microemulsion. The conductivity of the IL reverse microemulsions was decreased owing to the dilution of conducting polar cores by the addition of insulative PEG-400, indicating that PEG-400 was only solubilized into the reverse IL microemulsion interior. The conclusion was further supported by viscosity measurement.     

Use of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate in countercurrent chromatography

Room temperature ionic liquids (RTIL) are molten salts that are liquids at room temperature. Their liquid state makes them possible candidates as solvents in countercurrent chromatography (CCC), which uses solvents as both the mobile and stationary phases. The study focuses on 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF₆), an easy to synthesize and purify RTIL whose melting point is –8°C. It is shown that BMIM PF₆ behaves like a solvent of significant polarity (comparable with that of ethanol). The ternary phase diagram water–acetonitrile–BMIM PF₆ is given, because it was necessary to add acetonitrile to reduce the ionic liquid viscosity. The 40:20:40% w/w water–acetonitrile–BMIM PF₆ biphasic liquid system was found to be appropriate as a biphasic liquid system for CCC. Different aromatic solutes, including bases, acids, and neutral compounds, were injected into the CCC column to estimate their distribution constants between the ionic liquid-rich phase and the aqueous phase. The resulting K_il/w constants were compared with the corresponding literature octanol–water partition coefficients, K_o/w. The important drawbacks in the use of RTIL in CCC are clearly pointed out: high viscosity producing pressure build-up, UV absorbance limiting the use of the convenient UV detector, and non-volatility precluding the use of the evaporative light-scattering detector for continuous detection.     

EGCG在Tween80胶束体系中的性质(英文)

通过离子萃取技术,从黄山绿茶中提取高纯度儿茶素没食子酸酯(EGCG).在Tween 80/EGCG/H2O体系中,随着EGCG浓度增加,Tween 80临界胶束浓度和胶束动力学半径增大;随着Tween 80浓度增加,EGCG和Tween 80扩散系数减小,而EGCG的紫外-可见吸收光强度和荧光强度增加.对EGCG在Tween 80胶束中的定位也进行了讨论.     

Thermochemical properties of 1-butyl-3-methylimidazolium nitrate

Heat capacity for 1-butyl-3-methylimidazolium nitrate [C₄mim][NO₃] in the temperature range (5–370) K has been measured by adiabatic calorimetry. Temperatures and enthalpies of its phase transitions have been determined. Thermodynamic functions have been calculated for the crystalline and the liquid states. Phase transition temperatures for set of nitrate salts have been compared. Enthalpy of combustion and enthalpy of formation for crystalline [C₄mim][NO₃] have been determined using a static-bomb isoperibol combustion calorimeter. A correlation scheme for the estimation of C_p of ionic liquids has been developed.     

Structural studies of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/ p-xylene ionic liquid microemulsions.

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) forms nonaqueous microemulsions with p-xylene, with the aid of the nonionic surfactant TX-100. The phase behavior of the ternary system is investigated, and three microregions of the microemulsions-ionic liquid-in-oil (IL/O), bicontinuous, and oil-in-ionic liquid (O/IL)-are identified by conductivity measurements, according to percolation theory. On the basis of a phase diagram, a series of IL/O microemulsions are chosen and characterized by dynamic light scattering (DLS). The size of aggregates increases on increasing the amount of added polar component (bmimBF(4)), which is a similar phenomenon to that observed for typical water-in-oil (W/O) microemulsions, suggesting the formation of IL/O microemulsions. The microstructural characteristics of the microemulsions are investigated by FTIR and 1H NMR spectroscopy. The results indicate that the interaction between the electronegative oxygen atoms of the oxyethylene (OE) units in TX-100 and the electropositive imidazolium ring may be the driving force for the solubilization of bmimBF4 into the core of the TX-100 aggregates. In addition, the micropolarity of the microemulsions is investigated by using methyl orange (MO) as a UV/Vis spectroscopic probe. A relatively constant polarity of the microemulsion droplets is obtained in the IL microemulsion. Finally, a plausible structure for the IL/O microemulsion is presented.     

The kinetics of thermal decomposition of 1-butyl-3-methylimidazolium hexafluorophosphate

It is demonstrated that 1-butyl-3-methylimidazolium hexafluorophosphate decomposes in a vacuum in the temperature interval of T=(410 to 505) K according to zero-order kinetics with the activation energy EA=68.0+/-2.8 kJ.mol-1.     

The effect of water on the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate/TX-100/benzene ionic liquid microemulsions

The ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) forms nonaqueous microemulsions with benzene with the aid of nonionic surfactant TX-100. The phase diagram of the ternary system was prepared, and the microstructures of the microemulsion were recognized. On the basis of the phase diagram, a series of ionic liquid-in-oil (IL/O) microemulsions were chosen and characterized by dynamic light scattering (DLS), which shows a similar swelling behavior to typical water-in-oil (W/O) microemulsions. The existence of IL pools in the IL/O microemulsion was confirmed by UV/Vis spectroscopic analysis with CoCl2 and methylene blue (MB) as the absorption probes. A constant polarity of the IL pool is observed, even if small amounts of water are added to the microemulsion, thus suggesting that the water molecules are solubilized in the polar outer shell of the microemulsion, as confirmed by FTIR spectra. 1H NMR spectroscopic analysis shows that these water molecules interact with the electronegative oxygen atoms of the oxyethylene (OE) units of TX-100 through hydrogen-bonding interactions, and the electronegative oxygen atoms of the water molecules attract the electropositive imidazolium rings of [bmim][BF4]. Hence, the water molecules are like a glue that stick the IL and OE units more tightly together and thus make the microemulsion system more stable. Considering the unique solubilization behavior of added water molecules, the IL/O microemulsion system may be used as a medium to prepare porous or hollow nanomaterials by hydrolysis reactions.     

The role of 1-octyl-3-methylimidazolium hexafluorophosphate in anticorrosion coating formula development

A hydrophobic ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate, C₈mimPF₆) with a function of inhibiting corrosion was encapsulated at different concentrations in the copolymer of poly (methyl methacrylate) and poly (butyl acrylate) through miniemulsion polymerization. These latexes were coated on steel samples whose corrosion properties were evaluated by electrochemical techniques. It was found that increasing the C₈mimPF₆ concentration from 0 wt% to 30 wt%, the corrosion inhibition efficiency was remarkably improved from 41% to 89% based on the charge transfer resistance and from 64% to 87% based on the corrosion current density, respectively. The ionic liquid did not attend the reaction during latex preparation but behaved as corrosion inhibitors on the steel surface. Such an anticorrosion effect could be ascribed to the physical adsorption of the C₈mim⁺ cation on the reaction sites and the hydrophobicity enhancement resulting from the hydrophobic PF₆^? anion.     

1-正丁基-3-甲基咪唑溴化物离子液体TGA-FTIR研究

利用TGA-FTIR技术,研究了空气及氮气气氛下1-正丁基-3-甲基咪唑溴化物的热性能.结果表明,在不同的气氛下,在离子液体的沸点附近,存在一定的蒸汽压,随着温度的升高,1-正丁基-3-甲基咪唑溴化物主要以蒸气的形式汽化.在离子液体汽化过程中,未观察到离子液体发生明显的分解现象.在受热过程中,离子液体可能发生碳化作用,在空气气氛中,离子液体可能发生氧化作用,并且,离子液体的碳化速率与氧化速率基本接近.随着温度的升高,离子液体的氧化及碳化产物被进一步深度氧化.     

Selective extraction/isolation of hemoglobin with ionic liquid 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate (BtmsimPF6)

Ionic liquid was for the first time employed for selective isolation of heme-protein species. Direct extraction of hemoglobin into ionic liquid without using any concomitant reagent or extractant was carried out. Hemoglobin at the level of 100 ng μL⁻¹ could readily be quantitatively extracted into ionic liquid (IL) 1-butyl-3-trimethylsilylimidazolium hexafluorophosphate (BtmsimPF₆) in the absence of any co-existing extractants/additives at pH 7, at the same time; however, the other protein species do not interfere and remain in the aqueous phase. A back extraction efficiency of ca. 80% for 20 ng μL⁻¹ hemoglobin in ionic liquid phase was achieved with sodium dodecyl sulfate (SDS) solution as stripping reagent. ⁵⁷Fe Mossbauer spectra and circular dichroism (CD) spectra indicated that the penta-coordinated ferrous atom in hemoglobin provide a vacant or free coordinating position, which could be occupied by the cationic Btmsim⁺ moiety. The interaction/coordination reaction between the iron atom in the heme group of hemoglobin and the cationic ionic liquid moiety furnishes the driving force for facilitating fast transfer of hemoglobin into BtmsimPF₆. The present system was applied for selective isolation of heme-protein, i.e., hemoglobin from human whole blood without any pretreatment, giving rise to satisfactory results.     

离子液体表面活性剂1-丁基-3-甲基咪唑烷基硫酸酯的合成及其在水溶液中的聚集行为

采用离子交换法,由1-丁基-3甲基咪唑氯盐（C4mimCl）和烷基硫酸钠合成了一系列无卤素的阴离子表面活性离子液体—1-丁基-3-甲基咪唑烷基硫酸酯[C4mim][CnH2n 1SO4](n=8,12,16),利用表面张力仪、稳态荧光光谱等手段考察了表面活性离子液体在水溶液表面及体相中的聚集行为,结果表明,与传统无机反离子相比,有机咪唑阳离子[C4mim] 作为反离子的离子液体型表面活性剂具有较高的表面活性,[C4mim] 产生的氢键引起的抑制分子规则排列的作用小于其促进分子有序排列的疏水作用。长烷基链的阴离子是界面膜及胶束的主要组成成分,阴离子疏水烷基碳链的增长虽然可促进胶束的形成,但却在一定程度上抑制[C4mim] 离子参与界面或胶束的形成;阴离子所带烷基链越长,越不利于阳离子[C4mim]＋参与界面膜或胶束的形成,界面膜或胶束中表面活性剂排布越松散,即界面张力越大,体系中胶束聚集数较小。     

低分子烃类对吐温80-盐-水液-固析相分离的影响

报导了环己烷、庚烷等的加溶对非离子表面活性剂（吐温－80）液－固析相分离的影响,使小分子显色剂对甲酰基偶氮变色酸（CApF)、偶氮胂1（ArsenazoI)和配合物在低温下就易从盐水溶液相富集到表面活性剂固相,萃取率达95％。并对不己烷、庚烃的加溶机理及温度的作用做了探讨。     

Temperature dependence of the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate in aqueous solution

Many applications of ionic liquids (ILs) are closely related with their microstructure in mixtures. For example, morphology and pore size of the MCM-41 prepared in aqueous ILs are greatly dependent on the aggregation behavior of the ILs in water. Therefore, the study on the microstructure of ILs in aqueous solutions is of great importance. In this work, ¹H NMR, dynamic light scattering and attenuated total reflection infrared spectroscopy have been used to investigate the temperature effect on the structures of aqueous 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) solutions. It was shown that the size of the IL aggregates becomes larger with decreasing temperature. When the system temperature is below the upper critical solution temperature (UCST) of the binary mixture at about 4 °C, the aggregate size of the IL is larger than 1000 nm. Additionally, the two-dimensional IR results reveal that at low IL concentrations, H₂O can interact with [BF₄]⁻ prior to the CH groups of the imidazolium ring, whereas cation and anion of the IL tend to form aggregate at high IL concentrations. With the decrease of temperature, the interactions between cation and anion of the IL become stronger, but those between the IL and water become weaker, thereby resulting in the growth of the aggregate of cation with anion of the IL. This result may give a reasonable explanation for the origin of the UCST behavior of aqueous [C₄mim][BF₄] solution.     

非离子表面活性剂TWeen80相图的研究

本文研究了醇类（正丁醇、正戊醇、正辛醇和正癸醇）、油类（正十八烷、正十六烷、正十四烷、正十烷、正癸烷和正辛烷）、正十八烷含量以及NaCl浓度对Tween80／醇／油／水体系相图的影响。结果表明，NaCl浓度对Tween80／正辛醇／正十八烷／水体系相图的影响不明显；醇类随着炭原子数目的增加，O／W微乳液区面积增大，W／O微乳液区面积减小，微乳液区总面积增大；不同的油类形成的微乳液区面积由大到小的顺序是：正十六烷≈正十四烷＞正十二烷＞正癸烷＞正十八烷＞正辛烷；随着正十八烷含量的增加，微乳区面积减小。用2277热活性检测系统测定了石油菌B－2分别在非微乳液和助表面活性剂分别是正戊醇、正辛醇，油是正十八烷所形成的微乳液中生长的功率－时间曲线。结果表明微乳液培养基更适用于B－2利用高碳烷烃进行生长；正辛醇作助表面活性剂形成的微乳液培养基比正戊醇作助表面活性剂形成的微乳液培养更为有利；O／W型微乳液比W／O型微乳液对B－2的生长更为有利。     

Parametrization of 1-butyl-3-methylimidazolium hexafluorophosphate/nitrate ionic liquid for the GROMOS force field

A united-atom model of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]) and 1-butyl-3-methylimidazolium nitrate ([BMIM][NO(3)]) is developed in the framework of the GROMOS96 43A1(1) force field. These two ionic liquids are parametrized, and their equilibrium properties in the 298-363 K temperature range are subjected to validation against known experimental properties, namely, density, self-diffusion, shear viscosity, and isothermal compressibility. The ionic radial/spatial distributions, pi interaction, gauche/trans populations of the butyl tail, and enthalpies of vaporization are also reported. The properties obtained from the molecular dynamics simulations agree with experimental data and have the same temperature dependence. The strengths and weakness of our model are discussed.     

Measurement and correlation of solubility of carbon dioxide in 1-alkyl-3-methylimidazolium hexafluorophosphate ionic liquids

The solubility of carbon dioxide in the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate and 1-nonyl-3-methylimidazolium hexafluorophosphate was measured at temperatures of 293.15 and 298.15 K and pressure up to 4 MPa using a stoichiometric phase equilibrium apparatus. The measured data for 1-butyl-3-methylimidazolium hexafluorophosphate were in good agreement with existing literature data and new solubility data were reported for 1-nonyl-3-methylimidazolium hexafluorophosphate. The measured data were correlated using the group contribution non-random lattice fluid equation of state (GC-NLF EoS) proposed by Lee and co-workers. The group parameters for CG-NLF EoS were slightly modified at limited range to accommodate recent experimental data and better prediction at high pressure and long alkyl chains.