Liquid bmimPF6 Research Articles

On the way to greener furanic-aliphatic poly(ester amide)s: Enzymatic polymerization in ionic liquid

The polymerization of 2,5-furandicarboxylic acid (FDCA), one of the key building blocks for the preparation of furan polymers, is often accompanied with side reactions (e.g. decarboxylation). Due to the mild reaction conditions, enzymatic polymerizations became an excellent candidate to address this issue. Here, we present a green and effective method to prepare different furanic-aliphatic poly(ester amide)s (PEAFs) by applying two different approaches. PEAFs with Mw‾ up to 21 kg mol−1 were successfully synthesized by a Novozyme 435-catalyzed polycondensation of dimethyl 2,5-furandicarboxylate (DMFDCA) with aliphatic diols, diamines or amino alcohols, using toluene at 90 °C. Additionally, we were able to enhance the sustainability of the entire process by performing the polymerization in ionic liquids – BMIMPF6 and EMIMBF4. Using the ionic liquids (ILs) BMIMPF6 and EMIMBF4 as solvents, we were able to produce PEAFs with Mw‾ up to 7 kg mol−1. The different polarity of the solvents affects the enzyme activity and product solubility, thus also the final molecular weight of the PEAFs. Despite the lower molecular weight, the tested ILs result products with similar characteristics. All obtained PEAFs are semi-crystalline materials and decompose at a temperature around 390 °C with a Tm of around 77–140 °C and Tg of around 11–46 °C. Although still exemplified on the proof-of-concept production of sustainable materials, these findings pave the way to promote the transition from fossil-to bio-based polymers, as well as more environmentally friendly synthetic routes.

The Application of Ionic Liquid Composite Materials in Denitrification from Flue Gas

In this paper, ionic liquid BMIMPF6 was synthesized and characterized by IR and 1H NMR, and the properties, such as melting point, density, viscosity conductivity and the solubility with common solvents were detected. The NO2 solubility in composite materials composed of ionic liquid and organic base was also discussed, the absorption process was optimized and the absorption mechanism was speculated. The results showed that the purity of ionic liquid is 99% by 1H NMR. The properties of ionic liquid are basically identical with literature reported data. Under the optimum experimental conditions, the composite material composed of the ionic liquid and the organic alkali showed a high NO2 absorption amount of 0.311gNO2/g ionic liquid composite material, and the absorption process is a physical and chemical process. The ionic liquid composite material can be recycled for 4 times, and the absorption effect is basically unchanged.

Free-standing oligo(oxyethylene)-functionalized polythiophene with the 3,4-ethylenedioxythiophene building block: electrosynthesis, electrochromic and thermoelectric properties

A free-standing ordered polymer of P(EDT-E5-EDT) based on oligo(oxyethylene)-functionalized polythiophene with two 3,4-ethylenedioxythiophene units as building blocks was electrosynthesized successfully at a low oxidation potential, and comparatively investigated in three electrolytes of ACN/LiClO4, PC/LiClO4 and ionic liquid BmimPF6. Interestingly, one ordered film obtained from PC/LiClO4 resulted in its electrical conductivity up to 40Sm−1 depending on the mild growth condition. Among the fabricated P(EDT-E5-EDT) system, electronic transport is an important factor to receive a highest Seebeck coefficient of 35.9μVK−1. P(EDT-E5-EDT) films also exhibited favorable electroactivity and remarkable redox stability in especial. Moreover, the resultant films were demonstrated the electrochromic nature by color changing from salmon pink to blue, and broad absorption can be observed in near infrared region with the band gaps of 1.88–1.93eV. Further switching transmittance revealed that polymers had reasonable contrast ratios (17.35–52.36%), high coloration efficiencies (151.6–363.5cm2C−1), excellent switching stability and color persistence. The effective EDOT moieties in the chain plays a great role in the advanced properties, which could be developed to be semiconducting polymers in many electronic application areas.

Electrosynthesis of electroactive and fluorescent polyphenanthrenes via electropolymerization in BmimPF6

Poly(9,10-dihydrophenanthrene) (PDHP) and polyphenanthrene (PPhe) were synthesized electrochemically by direct anodic oxidation of their corresponding monomers in an ionic liquid BmimPF6. The electropolymerization performances of 9,10-dihydrophenanthrene (DHP) and phenanthrene (Phe), together with the properties of both polymers, including electrochemistry, optical properties, thermal degradation, and morphology were comparatively illustrated. FT-IR spectral analysis manifested that the polymerization of DHP occurred primarily at C(2) and C(7) positions, while Phe mainly through the coupling at C(9) and C(10) sites, in good agreement with previous results. Both PDHP (Eg=2.55eV) and PPhe (Eg=2.18eV) were electroactive and exhibited moderate redox stability, as well as good thermal stability. Furthermore, two polymers could emit yellow–green light, while PDHP showed higher fluorescence quantum yield of 0.14.

Ionic liquids increase the catalytic efficiency of a lipase (Lip1) from an antarctic thermophilic bacterium.

Lipases catalyze the hydrolysis and synthesis of triglycerides and their reactions are widely used in industry. The use of ionic liquids has been explored in order to improve their catalytic properties. However, the effect of these compounds on kinetic parameters of lipases has been poorly understood. A study of the kinetic parameters of Lip1, the most thermostable lipase from the supernatant of the strain ID17, a thermophilic bacterium isolated from Deception Island, Antarctica, and a member of the genus Geobacillusis presented. Kinetic parameters of Lip1 were modulated by the use of ionic liquids BmimPF6 and BmimBF4. The maximum reaction rate of Lip1 was improved in the presence of both salts. The highest effect was observed when BmimPF6 was added in the reaction mix, resulting in a higher hydrolytic activity and in a modulation of the catalytic efficiency of the enzyme. However, the catalytic efficiency did not change in the presence of BmimBF4. The increase of the reaction rates of Lip1 promoted by these ionic liquids could be related to possible changes in the Lip1 structure. This effect was measured by quenching of tryptophan fluorescence of the enzyme, when it was incubated with each liquid salt. In conclusion, the hydrolytic activity of Lip1 is modulated by the ionic liquids BmimBF4 and BmimPF6, improving the reaction rate and the catalytic efficiency of this enzyme when BmimPF6 was used. This effect is probably due to changes in the structure of Lip1 induced by the presence of these ionic liquids, stimulating its catalytic activity.

Prediction and measurement of phase equilibria for the extraction of BTX from naphtha reformate using BMIMPF6 ionic liquid

New Liquid–Liquid Equilibrium (LLE) data for three ternary systems namely; hexane+benzene+BMIMPF6, heptane+toluene+BMIMPF6, octane+o-xylene+BMIMPF6, and a fourth system consisting of synthetic naphtha reformate which is composed of hexane/heptane/octane+benzene/toluene/o-xylene+BMIMPF6 were obtained. The LLE were determined at T=298.15K and atmospheric pressure. Effect of the number of substituted methyls attached to aromatic rings was evaluated in terms of selectivity and extractive capacity of the ionic liquid BMIMPF6. The results showed a decrease of the extracted amount of aromatics by the ionic liquid as the increase of the number attached methyl groups in the corresponding aromatic systems. Thus, the extraction capability of aromatics by BMIMPF6 was in the order of benzene>toluene>o-xylene, either present in individual ternary systems or as mixture in one pseudo ternary system. Five thermodynamics models were used to correlate satisfactorily the LLE data for the four studied ternary systems. These are T-K-Wilson, Dortmund UNIFAC, ASOG, NRTL, and UINQUAC. Different strategies and modifications are made to the group contribution models UNIFAC and ASOG. These modifications showed an improved prediction compared to their original expressions. However, among all models considered in this study, the UINQUAC model gave the best predictions.

Nano-crystals of various lanthanide fluorides prepared using the ionic liquid bmimPF6

Lanthanide fluorides are important materials for a wide spectrum of applications. In this work, nano-sized crystalline fluorides of nearly all of the lanthanides were prepared via a one-pot reaction using the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) as both the solvent and as the fluorination agent and the appropriate lanthanide nitride as the source of the trivalent ion. The phase compositions of the samples (hexagonal, orthorhombic or a mixture of these) as well as the sizes of the nanocrystals were characterised by X-ray diffraction (XRD) and confirmed by high resolution transmission electron microscopy (HR-TEM). Fluorescence measurements were performed for all of the samples to gain insight into the optical properties of the samples.

Effect of Water on Interfacial Chemical Properties of Nonionic Surfactants in Hydrophobic Ionic Liquid bmimPF6

We studied the effect of water addition on interfacial properties and aggregate behavior of nonionic surfactants (polyoxyethylene alkyl ether; CnEm) in an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate; bmimPF₆). When a small amount of water was added to mixtures of CnEm and bmimPF₆, two breaking points (cac1, cac2) were observed in the surface tension/CnEm concentration plots, suggesting the formation of two kinds of aggregates. This two-step aggregate formation was also confirmed by the fluorescence probe method using pyrene. The particle size of the aggregates measured by dynamic light scattering (DLS) was around 200 nm at cac1, and decreased to 4 nm above cac2. These results, together with freeze-fracture TEM observations, showed that the aggregate formed at cac1 was water in bmimPF₆ emulsions, which then transformed to micelles solubilizing water in the palisade layer above cac2. This concentration-dependent aggregate formation was supported thermodynamically by studying the dependence of cacs on temperature and alkyl and POE chain lengths of the surfactant.

Supercapacitor based on electropolymerized polythiophene and multi-walled carbon nanotubes composites

Polythiophene (PTh) was electropolymerized onto multi-walled carbon nanotubes (MWCNT) modified glassy carbon (GC) electrode in ionic liquid bmimPF6 solution successfully. The different electrochemical behavior of thiophene in bmimPF6 solution was studied by cyclic voltammetry. The different morphologies of PTh films on MWCNT/GC and GC electrodes were characterized by scanning electron microscopy. Cyclic voltammetry test displays that PTh/MWCNT composites have better capacitive property than pure MWCNT and pure PTh. The galvanostatic charge–discharge and electrochemical impedance microscopy tests show that the PTh/MWCNT composites possess good capacitive characteristics. The specific capacitance of the supercapacitor is 110Fg−1. The long-term stability of the supercapacitor was also tested, and the result indicates that the specific capacitance still keeps 90% of the initial capacitance after 1000 consecutive charge–discharge cycles.

Lamellar Liquid Crystals of Brij 97 Aqueous Solutions Containing Different Additives

Lamellar liquid crystals of Brij 97 aqueous solutions were investigated by means of rheological techniques and SAXS at 25 °C, in the presence of various additives including isopropyl myristate, oleic acid, ionic liquid bmim-PF6 and bmim-BF4. The lamellar phases show high elasticity as indicated by their mechanical and discrete relaxation spectra, which is expected to be an advantage when they are used as drug delivery vehicles. It is noted that in comparison with other systems, the lamellar phase formed in the Brij 97/water/IPM system has the lowest storage and loss moduli, implying that it has a weak network strength and less stable internal structure. The Brij 97/water/oleic acid system is the most shear resistance, whereas the Brij 97/water/bmim-PF6 system exhibits fluid-like viscoelastic properties to some extent. These differences are analyzed through SAXS data for the different location of the additive in the lamellar phase.

Features of spin exchange in nitroxide biradicals in the ionic liquid bmimPF6

The intramolecular electron spin exchange has been studied by electron paramagnetic resonance (EPR) spectroscopy in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) for various nitroxide biradicals as a function of temperature and the nature of the connecting bridge between two >NO· centers. Temperature variations of the isotropic nitrogen hyperfine splitting constant a and exchange integral values |J/a| were measured from EPR spectra and analyzed. Thermodynamic parameters of the conformational rearrangements were obtained. The spin exchange in rigid and flexible biradicals dissolved in the ionic liquid bmimPF6 was compared with that in toluene solutions. Interesting features of the spin exchange in biradicals in ionic liquid were observed and explained as a result of the specific intramolecular conformational transitions. The first example of a rather rigid biradical molecule becoming flexible under the influence of an ionic liquid is reported.

Peculiarity of the liquid/vapour interface of an ionic liquid: study of surface tension and viscoelasticity of liquid BMImPF6 at various temperatures

We have measured the surface tension and the capillary wave spectra at the liquid/vapour interface of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate at various temperatures up to 400 K. From the weak temperature dependence of the surface tension a low value of the surface excess entropy of approximately 3.5 x 10(5) J K(-1) m(-2) results which is consistent with a strongly aligned surface layer of imidazolium cations previously predicted by MD-calculations. The capillary wave spectra recorded at different wave numbers in the range 170 cm(-1) < or = q < or =500 cm(-1) exhibit strong deviations from the behaviour expected for the free surface of simple liquids. With an extended dispersion relation including the contributions of surface dipole moment density gamma and shear surface excess viscosity mu the spectra have been analyzed. It is found that mu is negligibly small, whereas gamma substantially influences the capillary wave spectra. The electrostatic potential across the interface, which corresponds to the measured dipole moment densities, qualitatively agrees with simulation calculations. The distinct temperature dependence of gamma suggests that with increasing temperature an order-disorder transformation occurs in the surface layer.

Solvent extraction and extraction?voltammetric determination of phenols using room temperature ionic liquid

The phenolic compounds phenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 1-naphthol, 2-naphthol, and 4-chlorophenol are extracted nearly quantitatively from aqueous solution into the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) in molecular form at pH < p Ka. Picric acid is extracted efficiently in anionic form. Recovery of pyrocatechol and resorcinol is much lower. The effect of pH, phenol concentration, and volume ratio of aqueous and organic phases were studied. Ionic liquid BMImPF6 is shown to be suitable for extraction-voltammetric determination of phenols without back-extraction or addition of support electrolyte. The electrochemical window of BMImPF6 at various electrodes was determined, and voltammetric oxidation of phenols and reduction of nitrophenols in BMImPF6 was studied.

Ionic Phosphine Ligands with Cobaltocenium Backbone: Novel Ligands for the Highly Selective, Biphasic, Rhodium-Catalyzed Hydroformylation of 1-Octene in Ionic Liquids

The use of electron-poor phosphine-substituted cobaltocenium salts as ligands for the biphasic hydroformylation in ionic liquids has been investigated. Using improved oxidation methods, 1,1‘-bis(diphenylphosphino)cobaltocenium nitrate, 1,1‘-bis(diphenylphosphino)cobaltocenium hexafluorophosphate, and 1,1‘-bis[1-methyl(1-diphenylphosphino)ethyl]cobaltocenium hexafluorophosphate have been synthesized. 1,1‘-Bis(diphenylphosphinocobaltocenium hexafluorophosphate in particular proved to be a very suitable ligand for the biphasic hydroformylation of 1-octene in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF6), enabling high catalyst activity, high selectivity to the n-product, and no detectable catalyst leaching. In contrast to aqueous biphasic systems, the ionic liquid BMIM PF6 provides for the rhodium catalyst a low-coordinating medium with limited but sufficient solubility for 1-octene to allow high reaction rates.