Lipase‐catalyzed acylation of konjac glucomannan in ionic liquids

A comparative study was made of lipase‐catalyzed acylation of konjac glucomannan (KGM) with vinyl acetate as the acyl donor in five ionic liquids (ILs) and also in the presence of the organic solvent tert‐butanol (t‐BuOH). An obvious enhancement in enzyme activity and stability was observed using ILs as the reaction media when compared with t‐BuOH. The maximum degree of substitution (DS) of the modified KGM in ILs and t‐BuOH under the conditions employed is 0.71 and 0.54, respectively. The water activity (a_w) of the reaction system affected the acylation of KGM to some extent. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate (C₄MIm.BF₄) was the best IL medium for the reaction, and an a_w of 0.75 was optimum. It was also found that the nature of both the cation and the anion of ILs had an effect on the reaction. Candida antarctica lipase B immobilized on an acrylic resin (Novozym 435) displayed no acylation activity to KGM in 1‐butyl‐3‐methylimidazolium chloride (C₄MIm.Cl). The optimum reaction temperature for enzymatic acylation in ILs was shown to be 45‐55 °C. Enzymatic acylation of KGM in IL‐t‐BuOH co‐solvent systems was also investigated. When an appropriate amount of t‐BuOH was added to ILs, the DS of the modified KGM was enhanced. Additionally, the enzymatic acylation of KGM in all the media examined was shown to be regioselective, with acylation occurring predominantly at the C‐6‐OH. Copyright © 2006 Society of Chemical Industry     

High‐performance natural rubber latex composites developed by a green approach using ionic liquid‐modified multiwalled carbon nanotubes

The effect of multiwalled carbon nanotubes (MWCNTs) modified by a hydrophilic ionic liquids (ILs), including 1‐ethyl‐3‐methylimidazolium bromide and 1‐hexyl‐3‐methylimidazolium bromide, was studied. The obtained water‐suspensible carbon nanotubes (CNTs) were still homogeneously distributed in water a month after sonication. The microstructural development of filler networks and the uniform dispersion of MWCNTs in the presence of IL were analyzed by TEM. The apparent physical (cation–π/π–π) interaction between the MWCNTs and the IL was characterized by Raman spectroscopy, DSC, and TGA. Furthermore, high‐performance composites of natural rubber latex (NRL) and CNTs modified with IL were obtained by the liquid latex blending method. The CNTs were homogeneously distributed in the matrix and CNT–ILs improved the fatigue resistance and mechanical properties of the NRL/CNT–IL composites. This study demonstrates a simple and eco‐friendly approach to develop multifunctional advanced materials based on IL‐modified MWCNT elastomer composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46588.     

Electrical,mechanical, structural,and thermal behaviors of polymeric gel electrolyte membranes of poly(vinylidene fluoride‐co‐hexafluoropropylene) with the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate plus lithium tetrafluoroborate

Polymeric gel electrolyte membranes based on the polymer poly(vinylidene fluoride‐co‐hexafluoropropylene) [P(VdF–HFP)] with different weight percentages of the ionic liquid (IL) 1‐butyl‐3‐methylimidazolium tetrafluoroborate plus 0.3M lithium tetrafluoroborate (LiBF₄) salt were prepared and characterized by scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, complex impedance spectroscopy, pulse echo techniques, and Vickers hardness (H) testing. After the incorporation of the IL plus the salt solution in the P(VdF–HFP) polymer, the melting temperature, glass‐transition temperature (T_g), degree of crystallinity, thermal stability, elastic modulus (E), and hardness (H) gradually decreased with increasing content of the IL–salt solution as a result of complexation between the P(VdF–HFP) and IL. This was confirmed by FTIR spectroscopy. A part of the IL and LiBF₄ were found to remain uncomplexed as well. The ionic conductivity (σ) of the polymeric gel membranes was found to increase with increasing concentration of the IL–salt solution. The temperature‐dependent σs of these polymeric gel membranes followed an Arrhenius‐type thermally activated behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41456.     

Synergistic effects of two types of ionic liquids on the dispersion of multiwalled carbon nanotubes in ethylene–vinyl acetate elastomer: preparation and characterization of flexible conductive composites

Flexible conductive composites based on an elastomer, ethylene–vinyl acetate copolymer (EVM), and multiwalled carbon nanotubes (MWCNTs) were fabricated by melt‐blending and subsequent crosslinking. Two types of ionic liquids (ILs), tributylmethylammonium bis(trifluoromethanesulfonyl)imide and 1‐ethyl‐3‐methylimidazolium tetrafluoroborate, were used to modify the MWCNTs for the purpose of improving their dispersion in the polymer matrix. It was found that the MWCNTs modified by an individual IL form agglomerates in the EVM matrix, while the MWCNTs modified by the two types of ILs simultaneously disperse in the EVM matrix homogeneously. Moreover, nanocomposites based on the MWCNTs modified with the combination of the two ILs exhibit improved mechanical and electrical properties. The mechanism of such synergistic effects was investigated. It was found that EVM is miscible with tributylmethylammonium bis(trifluoromethanesulfonyl)imide and it is immiscible with 1‐ethyl‐3‐methylimidazolium tetrafluoroborate. On the other hand, MWCNTs show stronger interaction with 1‐ethyl‐3‐methylimidazolium tetrafluoroborate than tributylmethylammonium bis(trifluoromethanesulfonyl)imide. Therefore, the uniform dispersion of MWCNTs in the EVM matrix is attributed to ‘bridging’ effects of the two ILs due to the different interactions of the two ILs with MWCNTs and EVM. The application of MWCNTs modified with two types of ILs in a polymer matrix opens a new fabrication strategy for high‐performance polymer nanocomposites. © 2017 Society of Chemical Industry     

FTIR analysis of lignin regenerated from Pinus radiata and Eucalyptus globulus woods dissolved in imidazolium‐based ionic liquids

BACKGROUND: The dissolution of wood and the regeneration of compounds such as cellulose and lignin is one of the challenges currently facing biorefineries. Lignin can be processed and employed for value‐added products; therefore, environmentally friendly methods for wood solubilization and lignin regeneration are required and ionic liquids (ILs) offer an attractive alternative approach. RESULTS: Dissolution of Pinus radiata and Eucalyptus globulus woods in imidazolium‐based ILs (1‐butyl‐3‐methylimidazolium acetate, 1‐ethyl‐3‐methylimidazolium acetate and 1‐ethyl‐3‐methylimidazolium chloride) was studied as well as the regeneration of lignin from wood liquors. The dissolution of wood in ILs was verified using an optical microscope to select the most appropriate ILs and the best experimental time and temperature conditions. Lignin was regenerated from wood dissolved in 1‐ethyl‐3‐methylimidazolium chloride after 24 h at 150 °C by precipitation with an antisolvent. The regenerated solid was analyzed by Fourier transform infrared spectroscopy and compared with Indulin AT (reference). Furthermore, the influence of the wood dissolution time, the antisolvent employed and the antisolvent/wood solution ratio in the lignin recovery was studied. CONCLUSIONS: The current study shows that 1‐ethyl‐3‐methylimidazolium chloride can be employed effectively to dissolve wood at 150 °C for 24 h and lignin can be regenerated using methanol or ethanol as antisolvents. Copyright © 2012 Society of Chemical Industry     

Gas solubility in long‐chain imidazolium‐based ionic liquids

The gas solubility in 1‐dodecyl‐3‐methylimidazolium [C₁₂MIM] based ionic liquids (ILs) was measured at temperatures (333.2, 353.2, and 373.2) K and pressures up to 60 bar for the first time. The popular UNIFAC‐Lei model was successfully extended to long‐chain imidazolium‐based IL and gas (CO₂, CO, and H₂) systems. The free volume theory was used to explain the gas solubility and selectivity in imidazolium‐based ILs by calculating the fractional free volume and free volume by the COSMO‐RS model. Furthermore, the excess enthalpy of gas‐IL system was concerned to provide new insights into temperature dependency of gas (CO₂, CO, and H₂) solubility in ILs. The experimental data, calculation, and theoretical analysis presented in this work are important in gas separations with ILs or supported ionic liquid membranes. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1792–1798, 2017     

Use of 1‐hexyl‐3‐methylimidazolium bromide ionic liquid in the recovery of lactic acid from wine

BACKGROUND: Lactic acid has many different applications in a variety of industries including the food, cosmetics, packaging, leather and chemical industries. Current methodologies for lactic acid production are lengthy and complicated and more efficient methods are being sought. Some organic wastes contain lactic acid and our work investigates the use of ionic liquids (ILs) in the efficient and selective extraction of lactic acid from organic waste using wine as a model system. The ionic liquid was chosen based on its ability to selectively solvate and separate lactic acid from the remaining bulk waste material. RESULTS: Several ILs including 1‐hexyl‐3‐methylimidazolium chloride (hmimCl), 1‐hexyl‐3‐methylimidazolium bromide (hmimBr), 1‐hexyl‐3‐methylimidazolium iodide (hmimI) and N‐hexylpyridinium iodide (hpyrI) have been synthesized in high yield (68‐95%) using microwave technology. Lactic acid is soluble in each of the ILs synthesized with optimum results achieved with hmimBr where lactic acid is miscible in all proportions. HmimBr has been used to successfully separate and extract lactic acid from wine as confirmed by FTIR spectroscopy. Furthermore, it has been possible to recover the IL for recycle in subsequent extraction cycles where the efficiency for the extraction process increases with each recycle. CONCLUSION: HmimBr has been used for the first time in a novel process for the separation and recovery of lactic acid from wine, as confirmed by FTIR spectroscopy. This work demonstrates a novel process which can be applied to the recovery of lactic acid from organic waste. Copyright © 2012 Society of Chemical Industry     

1‐Butyl‐3‐methylimidazolium Tetrafluoroborate ([Bmim]BF4) Ionic Liquid: A Novel and Recyclable Reaction Medium for the Synthesis of vic‐Diamines

Aziridines undergo ring opening smoothly with various arylamines in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild and neutral conditions to afford the corresponding vicinal‐diamines in excellent yields with high regioselectivity. The recovered activated ionic liquids are recycled for four to five runs with no loss of activity.     

1‐Allyl‐3‐methylimidazolium halometallate ionic liquids as efficient catalysts for the glycolysis of poly(ethylene terephthalate)

Series of 1‐allyl‐3‐methylimidazolium halometallate ionic liquids (ILs) were synthesized and used to degrade poly(ethylene terephthalate) (PET) as catalysts in the solvent of ethylene glycol. One important feature of these new IL catalysts is that most of them, especially [amim][CoCl₃] and [amim][ZnCl₃], exhibit higher catalytic activity under mild reaction condition, compared to the traditional catalysts [e.g., Zn(Ac)₂], the conventional IL catalysts (e.g., [bmim]Cl), Fe‐containing magnetic IL catalysts (e.g., [bmim][FeCl₄]), and metallic acetate IL catalysts (e.g., [Deim][Zn(OAc)₃]). For example, using [amim][ZnCl₃] as catalyst, the conversion of PET and the selectivity of bis(hydroxyethyl) terephthalate (BHET) reach up to 100% and 80.1%, respectively, under atmospheric pressure at 175°C for only 1.25 h. Another important feature is that BHET can be easily separated from the catalyst and has a high purity. Finally, based on the experimental phenomena, in ‐situ infrared spectra, and experimental results, the possible mechanism of degradation with synthesized IL is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and dielectric properties of poly(ε‐caprolactone) compounded with “bucky gels”‐like mixture

Poly(ε‐caprolactone) (PCL) was melt compounded with “Bucky gels”‐like mixture that prepared by grinding multiwalled carbon nanotubes (MWNTs) and ionic liquids (ILs). Raman spectrum showed the significant interaction between ILs and MWNTs. The dielectric behavior of PCL nanocomposites based on unmodified and IL‐modified MWNTs was studied from 40 Hz to 30 MHz. The addition of ILs significantly enhanced the dielectric property of PCL/IL/MWNT ternary nanocomposites, which was much higher than that of the sum of PCL/IL with PCL/MWNT binary nanocomposites. The dielectric properties of PCL/IL/MWNT nanocomposites were mainly influenced by ILs in low frequency and were dominated by MWNTs in high frequency. SEM results revealed that a more uniform and fine dispersion of MWNTs were achieved throughout the PCL matrix because of ILs. The addition of ILs in nanocomposites changed the crystallinity of PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40231.     

Three‐Component One‐Pot Synthesis of α‐Hydroxylamino Phosphonates using Ionic Liquids

α‐Hydroxylamino phosphonates are synthesised in a one‐pot operation by three‐component coupling reactions of aldehydes, hydroxylamines and diethyl phosphite using 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild and neutral conditions. The recovered ionic liquids can be recycled for four to five runs without loss of activity.     

Thermodynamic validation of 1‐alkyl‐3‐methylimidazolium carboxylates as task‐specific ionic liquids for H2S absorption

Solubilities of H₂S in five 1‐alkyl‐3‐methylimidazolium carboxylates ionic liquids (ILs) have been measured at temperatures from 293.15 to 333.15 K and pressures up to 350 kPa. It is shown that these ILs have significantly larger absorption capacities for H₂S than those common ILs reported in the literature. The solubility is found to increase dramatically with the increasing alkalinity of the anions and slightly with the increasing length of the alkyl chains on the cations. It is further demonstrated that the absorption isotherms are typically nonideal. With the assumption of complex formation between H₂S and ILs, a reaction equilibrium thermodynamic model is developed to correlate the experimental solubilities. The model favors a reaction mechanism of AB₂ type that two IL molecules interact with one H₂S molecule. Thermodynamic parameters such as Henry's law constants, reaction equilibrium constants, and heat of complex formation are also calculated to evaluate the absorption process of H₂S in these ILs. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2227–2235, 2013     

Gloss reduction and morphological properties of polycarbonate and poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) blends with SAN‐co‐GMA as a reactive compatibilizer

The gloss properties of the polycarbonate (PC)/poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) (MABS) blend with styrene‐acrylonitrile‐co‐glycidyl methacrylate (SAN‐co‐GMA) as a compatibilizing agent were investigated. For the PC/poly(MABS)/SAN‐co‐GMA (65/15/20, wt %) blend surface, the reduction of gloss level was observed most significantly when the GMA content was 0.1 wt %, compared with the blends with 0.05 wt % GMA or without GMA content. The gloss level of the PC/poly(MABS)/SAN‐co‐GMA (0.1 wt % GMA) blend surface was observed to be 35, which showed 65% lower than the PC/poly(MABS)/SAN‐co‐GMA blend without GMA content. The gloss reduction was most probably caused by the insoluble fractions of the PC/poly(MABS)/SAN‐co‐GMA blend that were formed by the reaction between the carboxylic acid group in poly(MABS) and epoxy group in SAN‐co‐GMA. The results of optical and transmission electron microscope analysis, spectroscopy study, and rheological properties supported the formation of insoluble structure of the PC/poly(MABS)/SAN‐co‐GMA blend when the GMA content was 0.1 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46450.     

Crystallization behavior and isothermal crystallization kinetics of PLLA blended with ionic liquid, 1‐butyl‐3‐methylimidazolium dibutylphosphate

The crystallization behavior and isothermal crystallization kinetics of neat poly(l ‐lactic acid) (PLLA) and PLLA blended with ionic liquid (IL), 1‐butyl‐3‐methylimidazolium dibutylphosphate, were researched by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and wide angle X‐ray diffraction (WXRD). Similar to the non‐isothermal crystallization behavior of neat PLLA, when PLLA melt was cooled from 200 to 20°C at a cooling rate of 10°C min^?1, no crystallization peak was detected yet with the incorporation of IL. However, the glass transition temperature and cold crystallization temperature of PLLA gradually decreased with the increase of IL content. It can be attributed to the significant plasticizing effect of IL, which improved the chain mobility and cold crystallization ability of PLLA. Isothermal crystallization kinetics was also analyzed by DSC and described by Avrami equation. For neat PLLA and IL/PLLA blends, the Avrami exponent n was almost in the range of 2.5–3.0. It is found that t_1/2 reduced largely, and the crystallization rate constant k increased exponentially with the incorporation of IL. These results show that the IL could accelerate the overall crystallization rate of PLLA due to its plasticizing effect. In addition, the dependences of crystallization rate on crystallization temperature and IL content were discussed in detail according to the results obtained by DSC and POM measurements. It was verified by WXRD that the addition of IL could not change the crystal structure of PLLA matrix. All samples isothermally crystallized at 100°C formed the α‐form crystal. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41308.     

Gas–liquid mass‐transfer properties in CO2 absorption system with ionic liquids

The deficiency of mass‐transfer properties in ionic liquids (ILs) has become a bottleneck in developing the novel IL‐based CO₂ capture processes. In this study, the liquid‐side mass‐transfer coefficients (k_L) were measured systematically in a stirred cell reactor by the decreasing pressure method at temperatures ranging from 303 to 323 K and over a wide range of IL concentrations from 0 to 100 wt %. Based on the data of k_L, the kinetics of chemical absorption of CO₂ with mixed solvents containing 30 wt % monoethanolamine (MEA) and 0–70 wt % ILs were investigated. The k_L in IL systems is influenced not only by the viscosity but also the molecular structures of ILs. The enhancement factors and the reaction activation energy were quantified. Considering both the mass‐transfer rates and the stability of IL in CO₂ absorption system, the new IL‐based system MEA + [bmim][NO₃] + H₂O is recommended. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2929–2939, 2014     

Effect of added ionic liquids on the solubility and viscosity of dilute ionomer solutions in tetrahydrofuran

Solubility and viscosity behaviors of three ionomers with comparable ion contents of ca 6 mol%, i.e. poly(methyl methacrylate) sodium salt, sulfonated polystyrene calcium salt and sulfonated polystyrene sodium salt, were studied in a low‐polarity solvent, i.e. tetrahydrofuran (THF), containing an ionic liquid (IL). Upon addition to THF, the IL disrupts ionic aggregates to form a homogeneous solution and increases viscosity, because the IL disrupts intramolecular ionic aggregates at dilute concentration. Among eight ILs of the imidazolium family studied, 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate performs best. The effectiveness of ILs for disrupting ionic aggregates is discussed in terms of the structures of ionomers and ILs. © 2017 Society of Chemical Industry     

Separation and recovery of cellulose and lignin using ionic liquids: a process for recovery from paper‐based waste

BACKGROUND: The production of paper makes use of cellulose and lignin as a raw material, and almost all cellulose and lignin production comes from raw wood materials, contributing to deforestation and resulting in potential environmental harm. It is therefore beneficial to develop technologies for cellulose and lignin recovery for re‐use and sustainability of resources. RESULTS: Three imidazolium based ionic liquids (ILs), 1‐(2‐cyanoethyl)‐3‐methylimidazolium bromide (cyanoMIMBr), 1‐propyl‐3‐methylimidazolium bromide (propylMIMBr) and 1‐butyl‐3‐methylimidazolium chloride (butylMIMCl), were synthesised by microwave technology and fully characterised by mass spectrometry, thermogravimetric differential scanning calorimetry, thin layer chromatography, nuclear magnetic resonance and Fourier transform infrared spectroscopies. Cellulose and lignin were soluble in all three ILs with solubility being greatest in cyanoMIMBr. Regeneration of cellulose and lignin was achieved from saturated solutions of cellulose in IL and lignin in IL for all three ILs. The ILs propylMIMBr and butylMIMBr have been used for the first time in the separation and recovery of cellulose and lignin and regeneration of the IL from a mixture of cellulose and lignin in IL. FTIR analysis confirms successful recovery. CONCLUSIONS: This work demonstrates the ability of ILs to separate and recover cellulose and lignin from a mixed system. Copyright © 2009 Society of Chemical Industry     

Vapor Liquid Equilibria for Ionic Liquid/Ethanol/Water Systems and the Effect of Anion Hydrolysis

The performance of two tetrafluoroborate-based ionic liquids (ILs) as entrainers in the dehydration of water/ethanol azeotropic mixtures was evaluated. Isobaric vapor-liquid equilibrium (VLE) data were measured for the systems ethanol/water/1-butyl-3-methyl imidazolium tetrafluoroborate and ethanol/water /n-butylpyridinium tetrafluoroborate including the azeotropic region. VLE data for the ethanol/water, ethanol/IL, and water/IL binary mixtures were obtained at 100 kPa. The hydrolysis of the tetrafluoroborate anion was studied for both types of ILs by ¹⁹F NMR analysis. The hydrolysis of the tetrafluoroborate anion does not have much effect on the ethanol/water VLE. The ¹⁹F NMR analysis indicated that hydrolysis occurred at high mole fractions of water.     

Efficient and Eco‐Friendly Process for the Synthesis of Bis(1H‐indol‐3‐yl)methanes using Ionic Liquids

Indoles react smoothly with carbonyl compounds in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild reaction conditions to afford the corresponding bis‐indolylmethanes in excellent yields. These ionic liquids can be recovered and recycled in subsequent reactions without any apparent loss of activity.     

Effect of 1‐butyl‐3‐methylimidazolium iodide containing electrospun poly(vinylidene fluoride‐co‐hexafluoropropylene) membrane electrolyte on the photovoltaic performance of dye‐sensitized solar cells

Electrospun poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP) membrane was prepared from a solution of 16 wt % of PVdF‐HFP containing acetone/N,N‐dimethyl acetamide (7:3 wt %). The prepared electrospun PVdF‐HFP membrane (esPM) was then soaked in ionic liquid electrolyte containing 0.5M LiI, 0.05M I₂ , and 0.5M 4‐tert butylpyridine, 0.5M 1‐butyl‐3‐methylimidazolium iodide (BMImI) in acetonitrile to get electrospun PVdF‐HFP membrane electrolyte (esPME). The effect of various concentrations of BMImI containing esPME on ionic conductivity was studied by AC‐impedance measurements and the diffusion co‐efficients was determined by linear sweep voltammetry. The photovoltaic performance of a DSSC fabricated using 0.5M BMImI containing electrospun PVdF‐HFP membrane electrolyte (0.5M BMImI‐esPME) has power conversion efficiency (PCE) of 6.42%. But the stability of the DSSC fabricated using 0.5M BMImI‐esPME was considerably superior to that fabricated using 0.5M BMImI containing liquid electrolyte (0.5M BMImI‐LE). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42032.