Recycling Chiral Imidazolidin‐4‐one Catalyst for Asymmetric Diels–Alder Reactions: Screening of Various Ionic Liquids

Various imidazolium ionic liquids such as [Bmim]PF₆, [Bmim]SbF₆, [Bmim]OTf and [Bmim]BF₄ were screened for recycling an organic catalyst [(5S)‐5‐benzyl‐2,2,3‐trimethylimidazolidin‐4‐one ( 1 )] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF₆ or [Bmim]SbF₆. However, reactions in [Bmim]OTf or [Bmim]BF₄ gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

Effects of oxidant and dopants on the properties of cellulose/PPy conductive composite hydrogels

Cellulose/Polypyrrole (PPy) composite hydrogels were prepared by in situ chemically oxidative polymerization of pyrrole in the cellulose matrix. Ferric chloride (FeCl₃) was used as an oxidant and four sulfonic compounds were used as dopants in order to investigate the effects on the properties of cellulose/PPy conductive composite hydrogels. The extent of polymerization of PPy was determined by the amount of the oxidant and the composite hydrogels with oxidant at 0.3M?0.5M exhibited the higher conductivities for the intrachain and interchain conductivities of conductive polymers; the fracture stress of the composite hydrogels could be up to 26.25 MPa with a strain of 86.8% when the oxidant was at 0.5M. Doping is an efficient way to improve the conductivity of the composite hydrogels and four kinds of dopant were compared in this work. Long alkane chain and side group in dopants can increase the steric hindrance of PPy polymerization which resulted in the lower conductivity of the composite hydrogels compared to dopants with smaller steric hindrance. The conductivity of the composite hydrogel firstly increased and then decreased with the concentration of dopants from 0.1M to 1.0M in this work. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43759.     

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     

Influence of the dopant on the polypyrrole moisture content: Effects on conductivity and thermal stability

Having in mind to produce electrically conductive carbon–epoxy composite materials, we have filled an insulating epoxy resin with an electronic conducting polymer, polypyrrole (PPy). To select the PPy that best suits this process, various PPys were chemically synthesized. The syntheses were performed in water via a dispersion polymerization route using, initially, either FeCl₃ (PPy–Cl⁻) or (NH₄)₂S₂O₈ (PPy–HSO₄⁻) as oxidizing agents. Then, using (NH₄)₂S₂O₈ as the oxidant, two other PPy doped with aromatic species were obtained due to the dissolution of paratoluenesulfonic acid (PPy–TS⁻) or naphtalenesulfonic acid (PPy–NS⁻) in the reaction media. The characterization of the PPy samples by conductivity measurements, together with elemental and thermal analysis, showed that PPy–TS⁻ exhibits the highest conductivity and thermal stability, with the conductivity remaining steady over 14 days. In addition, a stabilizing effect of the aromatic anions was observed. The experiments have shown that moisture in the PPy cannot be entirely removed and that, with increasing moisture content, the conductivity also increases, indicating an ionic conductivity superimposed on the electronic conductivity usually observed in PPy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1567–1577, 1998     

Selective Separation of Toluene/n‐Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4]

Room‐temperature ionic liquids serve as alternative solvents for volatile organic compounds in liquid‐liquid extraction and liquid membrane separation. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was applied for extraction and supported ionic liquid membranes (SILMs) to separate toluene and n‐heptane. A high separation factor of toluene was achieved due to the strong interaction between ionic liquid cations and toluene. The mass transfer performance of the SILM process was enhanced by higher operating temperature. With the increase of initial toluene concentration in the feed phase, the mass transfer flux and removal efficiency of the SILM process were improved, while the separation factor decreased. The mass transfer flux was growing with the increase of flow rate at both sides. The SILM process was stable over a long time period due to the high viscosity and low volatility of [Bmim][BF₄].     

A Sponge‐Like 3D‐PPy Monolithic Material for Reversible Adsorption of Radioactive Iodine

3D polypyrrole (3D‐PPy) monolith is prepared by a simple chemical oxidation of pyrrole monomer using FeCl₃ as an oxidant. The as‐prepared PPy monolith exhibits an abundant porosity and with a mesopore size of about 9.1 nm in diameter. Taking advantage of its mesoprous feature as well as the unique chemical composition, the 3D‐PPy is employed as the porous medium for adsorption and removal of radioactive iodine from environment. A high iodine adsorption capacity of 1.6 g g⁻¹ for 3D‐PPy is obtained which is competing with that of those reported porous organic polymers. Besides, the adsorption kinetics and adsorption thermodynamic experiments show that the adsorption is dominated by the pseudosecond‐order kinetics and Langmuir models. Considering its simple and low cost‐effective preparing method, unique monolithic porous as well as π–π conjugated chemical structure, the resulted 3D‐PPy may be found useful applications for removal of radioactive iodine to address environmental issues.     

Preparation of the flexible polypyrrole/polypropylene composite fibrous film for electrochemical capacitor

Polypyrrole (PPy)/polypropylene fibrous membrane (PPF) composite materials with different PPy contents are prepared through in situ chemical oxidation polymerization in the pyrrole atmosphere at room temperature by dissolving the FeCl₃·6H₂O in methanol and acetonitrile as oxidant. The morphology of the composite is examined by scanning electron microscope (SEM), the conductivities of the composites are measured by convenient four‐probe method, and the properties of the capacitor cells assembled by the obtained PPy/PPF are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) measurements. The results show that the morphology, conductivity, and the capacitor property of the composite are influenced strongly by the solvent of the oxidant. The capacitor assembled by the PPy/PPF prepared by using acetonitrile as the solvent for FeCl₃^.6H₂O can adapt for quick charge/discharge, and exhibit the highest capacitance of about 72.5 F g^?1 when the PPy content is about 8.0%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Synthesis of highly conductive PPy/graphene nanosheets/NiO composite using ultrasonic technique

Highly conductive polypyrrole/graphene nanosheets/NiO (PPy/GNS/NiO) composites are fabricated via ultrasound technique using p‐toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The effects of the GNS and NiO loading on the electrical conductivity are investigated. The maximum conductivity of PPy/GNS/NiO composites about 24.39 S/cm found with 3 wt% GNS and 48.7 wt% NiO at room temperature. The results showed that the high‐aspect‐ratio structure of GNS played an important role in forming a conducting network in PPy matrix. The microstructures of PPy/GNS/NiO are evidenced by the scanning electron microscope and transmission electron microscope examinations. The cyclic voltammetry curves can be seen that the PPy/GNS/NiO composites also have good electrochemical performance, and it can be used as a supercapacitor electrode material. POLYM. COMPOS., 34:997–1002, 2013. © 2013 Society of Plastics Engineers     

Effect of Ionic Liquid 1-Butyl-3-Methyl-Imidazolium Dihydrogen Phosphate Pretreatment on Pyrolysis of Lignin

In order to improve the yield of liquid fraction and phenolics content during lignin pyrolysis, an effective method of lignin pyrolysis through the pretreatment of lignin by an acidic ionic liquid 1-butyl-3- methyl-imidazolium dihydrogen phosphate ([Bmim]H₂PO₄) at low temperature is investigated in this study. It is found that [Bmim]H₂PO₄ pretreatment increases the total yield of liquid products of lignin pyrolysis compared to that of original lignin. The [Bmim]H₂PO₄ pretreatment temperature significantly impacts the behaviors of the lignin pyrolysis. In the temperature range of 50 to 150°C, the yield of the overall liquid product obtained by pyrolysis of the sample pretreated at 50°C is the highest. After pretreatment, the [Bmim]H₂PO₄ can be efficiently recovered, but the structure and stability of the [Bmim]H₂PO₄ have been changed. The FTIR analysis shows that the ionic liquid [Bmim]H₂PO₄ pretreatment can break hydrogen bonds, ether linkages and ester bonds in lignin.     

One‐step synthesis of highly conductive PPy/graphite nanosheets/Gd3+ composites

Highly conductive polypyrrole/graphite nanosheets/Gd³⁺ (PPy/nanoG/Gd³⁺) composites are fabricated via in situ polymerization using p‐toluenesulfonic acid as a dopant and FeCl₃ as an oxidant. The effects of the graphite nanosheets and Gd³⁺ loading on the electrical conductivity are investigated. The maximum conductivity of PPy/nanoG/Gd³⁺ composites about 17.86 S/cm found with 3 wt% graphite nanosheets and 6 wt% Gd³⁺ at room temperature. The results showed that the high‐aspect‐ratio structure of graphite nanosheets played an important role in forming a conducting network in PPy matrix. Thermal gravimetric analysis demonstrates an improved thermal stability of PPy in the PPy/nanoG/Gd³⁺ composites. The microstructures of PPy/nanoG/Gd³⁺ are evidenced by the SEM and TEM examinations. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

Highly Efficient Oxidative Desulfurization of Fuels by Lewis Acidic Ionic Liquids Based on Iron Chloride

Acidic ionic liquids (ILs) have been employed as extractant and catalyst in the oxidative desulfurization (ODS) process of fuels in recent years. Several Lewis acidic ionic liquids [C₆³MPy]Cl/nFeCl₃ (molar fraction n = 0.5, 1, 2, 3) and [C₆MIM]Cl/FeCl₃ were prepared and used to remove the aromatic sulfur compounds dibenzothiophene and benzothiophene from fuels. In the ODS process, the used ILs acted as both extractant and catalyst with 30 wt % hydrogen peroxide aqueous solution as oxidant. The effects of Lewis acidity of ILs, IL's cation structure, molar ratio of O/S, reaction temperature, and different sulfur compounds on the sulfur removal of model oil were investigated. The results indicated that the sulfur removal for dibenzothiophene was affected by Lewis acidity of ILs and nearly reached 100 % by [C₆³MPy]Cl/FeCl₃ at conditions of 298 K, IL/oil mass ratio of 1/3, O/S molar ratio of 4/1, in 20 min. The sulfur removal of real gasoline reached 99.7 % after seven ODS runs in the [C₆³MPy]Cl/FeCl₃‐H₂O₂ system.     

Conducting polypyrrole‐coated banana fiber composites: Preparation and characterization

In this study, conducting banana fibers (BF) were obtained through in situ oxidative polymerization of pyrrole (Py) on the BF surface using ferric chloride hexahydratate (FeCl₃·6H₂O) as an oxidant. Suitable reaction conditions are outlined for the polymerization of Py: oxidant/monomer molar ratio, Py concentration and polymerization time of 2/1, 0.05 mol.L⁻¹ and 30 min, respectively. Under these conditions, high‐quality conducting fibers containing polyPy and BF (PPy‐BF) were obtained with an electrical resistivity as low as 0.54 Ω.cm. The PPy‐BF was blended with different concentrations of polyurethane (PU) by mixing the two components in a vacuum chamber and then applying compression molding. The electrical resistivity of composites with 25 wt% of PPy‐BF was around 1.8 × 10⁵ Ωcm, which is approximately 10⁸ times lower than that found for pure PU. Moreover, PU/PPy‐BF composites exhibited higher mechanical properties than pure PU and PU/PPy, indicating that these conducting fibers can also be used as reinforcement for polymer matrices. The properties of the PPy‐BF obtained by the method described herein open interesting possibilities for novel applications of electrically conducting fibers, from smart sensors to new conducting fillers that can be incorporated into several polymer matrixes to develop conducting polymer composites with good mechanical properties.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Effect of small amount of water on the dynamics properties and microstructures of ionic liquids

A series of systems of 1‐butyl‐3‐methylimidazolium acetate ([Bmim][Ac]), 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]), and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][Tf₂N]) with a small amount of water were simulated. Viscosities of systems were obtained by nonequilibrium molecule dynamics simulation and the results show that the viscosities change in different ways: for [Bmim][BF₄] and [Bmim][Tf₂N], viscosities decrease rapidly in the first stage, and then decrease slowly with the increase of water content. But for [Bmim][Ac], the viscosities increase first and then decrease. The unique phenomenon of [Bmim][Ac] can be attributed to the formation of chain‐like structure of anion???water???anion???. Hydrogen bond (HB) interaction between ion pairs is weakened, but the number of HB between water and anions increases with increase of water content. Besides, the microstructures of water in ionic liquids‐water systems were compared and found that the distribution of water is more concentrated in [Bmim][Tf₂N]‐H₂O system, while it is isotropy in [Bmim][Ac]‐H₂O system. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2248–2256, 2017     

Partitioning Behavior of Penicillin G in Aqueous Two Phase System Formed by Ionic Liquids and Phosphate

Abstract

An aqueous two‐phase system (ATPS) was presented with hydrophilic ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) and NaH₂PO₄ aqueous solution in this paper. The partitioning behavior of penicillin G in the ATPS was investigated. Concentrations of NaH₂PO₄, penicillin G, and [Bmim]Cl were evaluated to determine their effects on the partition coefficient and extraction yield of penicillin G. It was found that both of partition coefficient and extraction yield strongly depended on the concentration of [Bmim]Cl, penicillin and NaH₂PO₄. A high extraction yield of 93% was achieved with the following parameters: NaH₂PO₄ · 2H₂O 40% (wt%), penicillin 45000～50000 u/ml, [Bmim]Cl 20～21% (wt%). The [Bmim]Cl/NaH₂PO₄ system was also applied in a real filtration of penicillin G fermentation broth and the extraction yield was averaged at 91.5%. It is worthy noting that the working pH value of ATPS was at the range of 5～6, no emulsification and protein denaturation could be observed.     

Multiwalled carbon nanotubes/polypyrrole/graphene/nonwoven fabric composites used as electrodes of electrochemical capacitor

The reduced graphene oxide/nonwoven fabric (rGO/NWF) composites have been fabricated through heating the NWF coated with the mixture of GO and HONH₂·HCl at 130°C, during which the GO is chemically reduced to rGO. Then the composites of polypyrrole (PPy)/rGO/NWF have been prepared through chemically polymerizing pyrrole vapor by using the FeCl₃·6H₂O adsorbed on rGO/NWF substrate as oxidant. Finally, multiwalled carbon nanotubes (MWCNTs) are used as conductive enhancer to modify PPy/rGO/NWF through dip‐dry process to obtain MWCNTs/PPy/rGO/NWF. The prepared composites have been characterized and their capacitive properties have been evaluated in 1.0M KCl electrolyte by using two‐electrode symmetric capacitor test. The results reveal that MWCNTs/PPy/rGO/NWF possesses a maximum specific capacitance (C_sc) of about 319 F g^?1 while PPy/rGO/NWF has a C_sc of about 277.8 F g^?1 at the scan rate of 1 mV s^?1 and that optimum MWCNTs/PPy/rGO/NWF retains 94.5% of initial C_sc after 1000 cycles at scan rate of 80 mV s^?1 which is higher than PPy/rGO/NWF (83.4%). Further analysis reveals that the addition of MWCNTs can increase the charger accumulation at the outer and inner of the composites, which is favorable to improve the stability and the rapid charge‐discharge capacity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41023.     

Controllable growth of TiO2-B nanosheet arrays on carbon nanotubes as a high-rate anode material for lithium-ion batteries

To meet the increasing demands of electrode materials with high capacity and fast charge–discharge capability for next-generation lithium-ion batteries (LIBs), well-designed nanostructures of carbon-supported metal oxides have been extensively investigated. Here we design and fabricate a novel hybrid nanoarchitecture of carbon nanotubes (CNTs) coated with TiO₂-B nanosheets (CNTs@TiO₂-B NSs) by using an imidazolium-based ionic liquid of [Bmim][BF₄] as a guiding agent. The ionic liquid of [Bmim][BF₄] interacts with CNTs via cation-π interactions and further guides the in situ growth of TiO₂-B nanosheet arrays onto CNTs. The resultant hybrid nanoarchitecture possesses a large specific surface area, porous nature, and abundant electron/lithium pathways. These features combined with the fast pseudocapacitive behavior and the reduced ion-diffusion length of TiO₂-B nanosheet arrays, contribute to a high reversible capacity and superior rate capability for LIB applications.     

Performance and pressure drop of CO2 absorption into task-specific and halide-free ionic liquids in a microchannel

The gas–liquid two-phase flow pattern, absorption rate and pressure drop of CO₂ absorbed into the aqueous solution of the task-specific ionic liquids (1-aminopropyl-3-methylimidazole tetrafluoroborate [Apmim][BF₄] and 1-hydroxyethyl-3-methylimidazole tetrafluoroborate [OHemim][BF₄]) and halide-free ionic liquid 1-butyl-3-methylimidazolium methylsulfate [Bmim][CH₃SO₄] were investigated in a microreactor. The absorption mechanism of the three ionic liquids was analyzed employing the ¹³C NMR spectroscopy. The [Apmim][BF₄] was found to have the best ability of CO₂ capture compared with the other two ionic liquids, as chemical absorption occurred between [Apmim][BF₄] and CO₂, while only physical absorption took place between [OHemim][BF₄]/[Bmim][CH₃SO₄] and CO₂. The sequence of CO₂ absorption rate in three ionic liquids aqueous solutions is: [Apmim][BF₄] > [Bmim][CH₃SO₄] > [OHemim][BF₄]. Furthermore, the effects of gas–liquid flow rate and ionic liquids concentration on CO₂ absorption rate and pressure drop were studied, the pressure drop models based on various flow patterns were proposed.     

Preparation and characterization of polyaniline–polypyrrole composite from polyaniline dispersions

Polyaniline–polypyrrole (PANI‐PPy) composite was prepared by in situ polymerization of pyrrole in PANI dispersion using FeCl₃·6H₂O as oxidant and sodium dodecyl benzene sulfonate (SDBS) as surfactant. Different synthesis conditions of PANI dispersion including the relative concentration of aniline and SDBS and the amount of acid (HCl) on the morphology and conductivity of the resulting composites were investigated. Fourier transformation infrared (FTIR) spectra, X‐ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), X‐ray diffraction (XRD) patterns, and contact angles of the composites showed there existed certain interaction between PANI (or PANI‐SDBS) and PPy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3523–3529, 2007     

A novel [Bmim]PW/HMS catalyst with high catalytic performance for the oxidative desulfurization process

To effectively reduce the sulfur content in model fuel, [Bmim]PW/HMS catalyst was synthesized through impregnating the hexagonal mesoporous silica (HMS) support by phosphotungstic acid (HPW) and ionic liquid [Bmim] HSO₄. Physical structure characterizations of the catalysts showed that HMS retained mesoporous structure, and [Bmim] PW was well dispersed on the support of HMS. The catalytic activity of the [Bmim]PW/HMS was evaluated in the oxidative desulfurization process, and the optimal reaction conditions including loading of the catalysts, reaction temperature, catalyst amount, O/S (H₂O₂/sulfur) molar ratio and agitation speed were investigated. Under the optimal reaction conditions, the conversion of benzothiophene (BT), dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT) could reach 79%, 98%, 88%, respectively.     

Synthesis and antibacterial activity of alkylated chitosan under basic ionic liquid conditions

A novel method to synthesize alkylated chitosan with [Bmim]OH basic ionic liquid as alkaline reagent is reported for the first time. Chitosan was alkalized by [Bmim]OH basic ionic liquid before it was reacted with various alkyl halides, and a series of alkylated chitosans with different carbon chain substituents were prepared. The structure of alkylated product was characterized by IR, ¹H‐NMR, and XRD. The reusability of the ionic liquid was also investigated, and the experimental results indicated that there was no noticeable change for the degree of substitution (DS) of alkylated chitosan after the ionic liquid was reused for three times. The antibacterial activities of the target products were investigated according their minimum inhibitory concentration (MIC) against K. pneumoniae, P. aeruginosa, E. aerogenes, E. coil, S. epidermidis, and S. aureus, and the results indicated that E‐CTS, B‐CTS, and D‐CTS could exhibit excellent antibacterial activities against P. aeruginosa, and their MIC were 128, 128, and 256 μg mL^?1, respectively. Meanwhile, the antibacterial activities of alkylted chitosans were decreased with the growth of the DS or the growth of the carbon chain. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40052.