Ionic liquid recovery alternatives in ionic liquid‐based three‐phase partitioning (ILTPP)

Ionic liquid‐based three‐phase partitioning (ILTPP) is a promising technique to recover high‐added value proteins at the liquid–liquid interface. Its economic and environmental performance highly depends on the net ionic liquid consumption. Alternatives to maximize the fraction of ionic liquid that can be recycled are studied. It is demonstrated that the addition of extra salt, previously proposed in literature, has a very limited effect on ionic liquid recovery for relatively high protein concentrations in the feed stream, and that it may even lead to an increase of the ionic liquid losses under certain conditions. However, small additions of salt are shown to be effective and profitable from an economic point of view. Vacuum evaporation is shown to allow for the complete ionic liquid and salt recovery, reinforcing the sustainability and viability of ILTPP processes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3577–3586, 2014     

1,2,3-Triazolium-based poly(acrylate ionic liquid)s

Nitroxide-mediated radical polymerization of a tailor-made acrylate carrying a 1,2,3-triazole group with an undecanoyl spacer affords a well-defined (M_n = 7860 g mol⁻¹ and D = 1.39) neutral polyacrylate precursor. A series of 1,2,3-triazolium-based poly(ionic liquid)s (TPILs) is then obtained by straightforward quaternization of the 1,2,3-triazole groups with methyl iodide and subsequent anion metathesis reactions. Among the prepared materials, TPIL with bis(trifluoromethane)sulfonimide anion exhibits low glass transition temperature (T_g = −40 °C), high thermal stability (T_d10 = 325 °C) and anhydrous ionic conductivity of 4 × 10⁻⁶ S cm⁻¹ at 30 °C, as measured by differential scanning calorimetry, thermogravimetric analysis and broadband dielectric spectroscopy, respectively.     

Functional mesoporous poly(ionic liquid)-based copolymer monoliths: From synthesis to catalysis and microporous carbon production

Ionic liquid-functionalized mesoporous polymeric networks with specific surface area up to 935 m²/g have been successfully synthesized one pot by solvothermal copolymerization of divinylbenzene and monomeric ionic liquids. The as-obtained polymers exhibit a monolithic structure featuring large pore volumes, an abundant mesoporosity and an adjustable content of ionic liquids. The effect of the reaction conditions on the pore structure has been studied in detail. These poly(ionic liquid)-based porous networks (PILPNs) have then been employed as precursors in two distinct applications, namely organocatalysis and production of microporous carbon monoliths. Selected organocatalyzed reactions, including carbonatation of propylene oxide by cycloaddition with carbon dioxide, benzoin condensation, and cyanosilylation of benzaldehyde have been readily triggered by PILPNs acting as crosslinked polymer-supported (pre)catalysts. The two latter reactions required the prior deprotonation of the imidazolium salt units with a strong base to successfully generate polymer-supported N-heterocyclic carbenes, referred to as poly(NHC)s. Facile recycling and reuse of polymer-supported (pre)catalysts was achieved by simple filtration owing to the heterogeneous reaction conditions. Furthermore, PILPNs could be easily converted into microporous carbon monoliths via CO₂ activation.     

Clickable poly(ionic liquid)s for modification of glass and silicon surfaces

Covalent attachment of poly(ionic liquid)s (PILs) by click chemistry on glass or silicon (Si) surfaces was performed. Poly[1-(4-vinylbenzyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide] (polyVBBI⁺Tf₂N⁻), and copolymers of polyVBBI⁺Tf₂N⁻ with fluorescein O-methacrylate were synthesized by conducting an atom transfer radical polymerization (ATRP) from initiators containing azide or thioacetate groups. The azide- and thiol-terminated PILs were then successfully grafted onto alkyne and alkene modified glass/Si wafers by thermal azide–alkyne cycloaddition and photoinitiated thiol-ene click reactions, respectively. The modified surfaces were characterized by contact angle measurements and ellipsometry. The fluorescent PIL functionalized surfaces showed strong fluorescence under UV irradiation. This procedure of tethering PILs to substrates also provides an easy way to change the surface hydrophilicity by replacing the anions in the grafted PILs. The present approach could be readily applied for surface modifications with other types of PILs or their copolymers to achieve different functionalities on various surfaces.     

Carbon nanotube–polyaniline composites

The last decade has seen a growing interest in hybrid electrically conducting nanocomposites. This article aims to provide a detailed overview of the present status of research in carbon nanotube–polyaniline (CNT/PANI) composites, from processing to structural and property evaluations. CNT/PANI are synthesized by electrochemical and chemical processing. When chemical methods are used, the main challenge is to obtain processable CNT/PANI in the emeraldine salt (ES) form composites. Stable dispersions of ES–CNT in organic media are prepared using the post doping method, inverse emulsion polymerization, or ex situ polymerizations. On the contrary, stable water dispersions of CNT/ES are prepared using hydrophilization of a preformed CNT/ES composite, direct synthesis of micelle–CNT hybrid templates, interfacial polymerization, covalent functionalization of CNT with a water soluble polymer, or using electrostatic interactions between two oppositely charged ES and CNT aqueous colloids. Moreover, the strategies for the synthesis of ternary CNT/PANI composites incorporating noble metal nanoparticles, metal oxide, or graphene sheets are also presented and analyzed in depth. Finally, we give a review of potential applications, including chemical sensors, capacitors, fuel cells and electronic devices.     

The adjustable synergistic effects between acid–base coupling bifunctional ionic liquid extractants for rare earth separation

Two of the most widely used industrial extractants for rare earth elements (REEs), that is, di(2‐ethylhexyl)phosphoric acid (HDEHP) and 2‐ethyl(hexyl) phosphonic acid mono‐2‐ethylhexyl ester (HEH[EHP]) were developed into [DEHP]^? type acid–base coupling bifunctionalized ionic liquids (ABC‐BILs) and [EHEHP]^? type ABC‐BILs, respectively. The combinations of ABC‐BIL extractants revealed synergistic effects for REEs. Seven different combinations of ABC‐BILs and five kinds of REEs confirmed the novel synergistic extraction. Some synergy coefficients of the combined ABC‐BILs were bigger than those of mixed HDEHP and HEH[EHP] by two orders of magnitude. The first synergistic extraction produced by ionic liquid extractants in the field of solvent extraction was reported in this article. The novel synergistic extraction from combined ABC‐BILs extractants revealed highly efficient and environmentally friendly potential in both of academic research and industrial application for REEs separation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3859–3868, 2014     

Phase equilibria and structural properties of thiophene/[Bmim][BF4]: A molecular insight from monte carlo simulations

The phase equilibria of thiophene in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) is calculated by Monte Carlo simulation in Gibbs ensemble using a united atom force field. The liquid density of studied ionic liquid and the vapor pressure of thiophene in [Bmim][BF₄] were compared with corresponding experimental data reported in the literature, and a good agreement was obtained. In order to describe the solubility of thiophene in this ionic liquid, we have calculated the radial distribution functions and spatial distribution functions of thiophene/IL mixtures to study the interaction of thiophene with cations and anions of [Bmim][BF₄] in the liquid phase. The local composition concept in fluid was also examined to give further insight into the liquid structure. The results show that thiophene is well organized around the terminal carbon atom of the butyl or methyl chain attached to the imidazolium ring of cations and tends to adopt a symmetrically distribution on the anions. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3916–3924, 2014     

Slip Length Measurements Using µPIV and TIRF-Based Velocimetry

The goal of this paper is to review progress (mostly recent) made in micro and nanovelocimetry, focusing on two techniques: µPIV (microparticle image velocimetry) and nanoPTV (nanoparticle tracking velocimetry). The paper focuses on the measurement of slippage (taken as a benchmark for these techniques), concentrating on work done in our group. We review the developments of µPIV that led, in the last ten years, to the achievement of 100 nm accuracy in the measurement of slip lengths. Later, this approach was complemented by nanoPTV, which recently obtained ±5 nm precision. Here, we also mention recent application of these techniques toward better characterization of microgel and polymer flows. As a whole, the two techniques have conveyed valuable information on flow behavior within and close to the boundaries of microchannels, on the importance of wetting, and on the role of surface heterogeneities. µPIV is commercially available but nanoPTV is not mature. Interesting instrumental developments are expected in the future for the latter technique.     

Preparation of oligochitosan via In situ enzymatic hydrolysis of chitosan by amylase in [Gly]BF4 ionic liquid/water homogeneous system

The preparation of oligochitosan with excellent performance via in situ enzymatic hydrolysis of chitosan by amylase in ionic liquid system is reported. It has been found that [Gly]BF₄ ionic liquid leads to the good solubility and assistant degradation for chitosan, as well as good biocompatibility for amylase. In the homogeneous system that contained 1.0 g chitosan (degree of deacetylation = 88.5%) and 99.0 g 2 wt % [Gly]BF₄ aqueous solution, oligochitosan with 2200 viscosity‐average molecular weight has been obtained after 0.12 g amylase being used for 3 h at 50°C and pH 5.0. This result is superior to that conducted in acetic acid system. Moreover, [Gly]BF₄ can be easily separated from the product and reused with only slight performance loss (oligochitosan product with 2700 viscosity‐average molecular weight has been obtained after [Gly]BF₄ being reused for five times). In addition, the mechanism for enzymatic hydrolysis of chitosan in [Gly]BF₄ ionic liquid has been described. The research on the moisture‐absorption, ‐retention, and antibacterial activity of oligochitosan product shows that the smaller molecular weight would bring the better moisture‐absorption and antibacterial properties. The oligochitosan product with 2200 viscosity‐average molecular weight exhibits preferable antibacterial properties to S. aureus and E. coli. At the same time, the moisture‐absorption and ‐retention capacity of the above product can reach 32% (relative humidity (RH) = 43%), 62% (RH = 81%), and 150% (RH = 43%), 35% (dry silica gel) respectively. The enzymatic preparation of oligochitosan through [Gly]BF₄ ionic liquid/water homogeneous system can be an efficient and environment‐friendly method for academics and industry. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41152.     

纳米Fe3O4颗粒对离子液体润滑减摩及电控增摩性能的影响

目的 提高离子液体在常态环境下的润滑减摩能力及电场条件下的电控增摩响应特性。方法 将合成油酸改性后的Fe3O4纳米颗粒分散添加到离子液体中,制备了不同浓度的离子液体基铁磁流体,通过利用自制载流摩擦磨损试验机,分别模拟测试了常态环境与电场环境下纯离子液体与离子液体基铁磁流体摩擦因数的变化,同时利用白光干涉仪、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射(XRD)对比分析了磨损形貌。结果 在常态环境下,Fe3O4纳米颗粒的“滚珠减摩效应”显著提高了离子液体在常态环境中的润滑效果。随着纳米Fe3O4颗粒质量分数的增加,磨痕逐渐变得光滑平整,剥落和磨粒聚集现象也逐渐消失,尤其是当质量分数为30%时,试样磨痕内部仅有较浅的犁沟和轻微的划痕,此时的摩擦因数也展现出了极低的水平,约为0.04,远低于纯离子液体润滑时的0.085。同时纳米颗粒的“电致沉积效应”增强了离子液体在电场环境中的电控增摩响应能力,当电流强度达到20 A时,对于质量分数为30%的离子液体基铁磁流体,摩擦因数瞬时提高了近1倍,增幅达到了0.039,是相同条件下纯离子液体摩擦因数增长幅度的4倍。结论 将合成改性后的Fe3O4纳米颗粒分散添加到离子液体中,成功制备了离子液体基铁磁流体,并且通过调控纳米颗粒含量,显著提高了离子液体的润滑性能和电控增摩响应能力。