Increasing Ionic Liquid Content Research Articles

Enhanced performance of solid polymer electrolytes combining poly(vinylidene fluoride-co-hexafluoropropylene), metal-organic framework and ionic liquid for advanced solid state lithium-ion batteries

The search for sustainable and high-performance materials for lithium-ion batteries is leading to significant advances in solid polymer electrolyte (SPE) technology. However, the current drawbacks of this approach prove the need for further research and development in the field. Herein, novel ternary solid polymer electrolytes have been developed using varying loads of MOF-808 metal-organic framework and [BMIM][SCN] ionic liquid (IL) incorporated in a poly(vinylidene fluoride-co-hexafluoropropylene) matrix. The solid polymer electrolytes were evaluated at morphological, structural, thermal, mechanical and electrochemical levels, and their performance in cycling battery testing was assessed. The results showed a homogeneous structure throughout all the samples and a good dispersion of the distinct components. The polymer polar phase and degree of crystallinity of the samples are increased with increasing IL content, and the thermal and mechanical properties are appropriate for battery application. The ionic conductivity of the samples reaches maximum values of 4.68 × 10−5 S‧cm−1 at room temperature, lithium transference numbers up to 0.65, and high electrochemical stability, making them well-suited for battery applications. The assembled stability after 50 cycles at C/10 with a discharge capacity value of 150 mAh‧g−1 at room temperature was tested/derived. The obtained results show the potential of this system for high performance room temperature solid polymer electrolytes.

Development of an ion gel membrane containing a CO2-philic ionic liquid in interpenetrating semi-crystalline and crosslinkable polymer networks

We developed a tough and highly CO2-permeable ion gel membrane composed of a CO2-philic ionic liquid (IL), 1-ethyl-3-methylimidazolium tetracyanoborate ([Emim][B(CN)4]), and an interpenetrating polymer network (IPN) composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and crosslinkable poly(ethyl acrylate-co-N-succinimide acrylate) (poly(EA-co-NSA)). The semi-crystalline PVDF-HFP and IL-philic poly(EA-co-NSA) networks endowed the ion gel membrane with high mechanical strength and good IL-holding properties. The high mechanical strength and good IL-holding properties achieved by the polymer networks provided the ion gel membrane with high and selective CO2 permeability under pressurized conditions at a trans-membrane pressure difference of 250 kPa. In addition, the high CO2 absorbability of [Emim][B(CN)4] provided the ion gel membrane with a CO2 permeability of more than 2500 barrer and a CO2/N2 permselectivity of approximately 20 at an elevated temperature of 80 °C. It was also demonstrated that the CO2 permeability of the IPN ion gel membrane increased with increasing IL content. The IPN ion gel membrane with an IL content of 85 wt% had a CO2 permeability of 2243 barrer and a CO2/N2 permselectivity of 43 at 30 °C. The excellent CO2 permeability and CO2/N2 permselectivity were not changed by physical aging for more than one week.

High-Performance Sustainable Electrochromic Devices Based on Carrageenan Solid Polymer Electrolytes with Ionic Liquid.

The development of sustainable functional materials with strong potential to be applied in different areas has been growing and gaining increasing interest to address the environmental impact of current materials and technologies. In this scope, this work reports on sustainable functional materials with electrochromic properties, based on their increasing interest for a variety of applications, including sensing technologies. The materials have been developed based on a natural derived polymer, carrageenan, in which different amounts of the ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) were blended. It is shown that the addition of different amounts of IL to the carrageenan matrix does not affect the properties of the samples in terms of morphology or physicochemical and thermal properties, the most significant difference being the increase of the ionic conductivity with increasing IL content, ranging from 2.3 × 10-11 S·cm-1 for pristine carrageenan to 4.6 × 10-4 S·cm-1 for the samples with 5 and 60 wt % IL content, respectively. A electrochromic device has been developed based on the different IL/carrageenan samples as electrolyte and poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) as electrodes. Spectroelectrochemistry testing demonstrates functional devices at low voltages between 0.3 and -0.9 V. Among the different samples, the one with 15 wt % IL content presents the best conditions for application, presenting an oxidation time of 6 s, a reduction time of 8 s, and a charge density of 1150 and 1050 μC·cm-2 for oxidation and reduction, respectively. The same sample also presents excellent optical density as a function of load density, presenting an optical switch (Δ%Tx) of 99%. Thus, it is demonstrated that it is possible to develop high efficiency and sustainable electrochromic devices based on natural polymers and ionic liquids.

Plasticizing effect of 1‐butyl‐3‐methylimidazolium bromide content on poly(vinyl alcohol)

AbstractPVA/IL composites were successfully prepared with an ionic liquid (IL), 1‐butyl‐3‐methylimidazolium bromide and poly(vinyl alcohol) (PVA). The plasticizing effect of IL on PVA was investigated using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), X‐ray diffraction (XRD), thermogravimetric analysis (TGA) and melt flow index (MI) measurements. FTIR analysis indicated that the anion (Br−) of IL could form hydrogen bonds with the hydroxyl groups of PVA. With an increase of IL, –OH absorption peaks of PVA/IL composites shifted to higher wavenumbers. DSC analysis showed that both melt and crystallization temperatures of the PVA/IL composites decreased as IL content increased. XRD analysis showed that the degree of crystallinity of the PVA/IL composites had a decreasing trend with an increase of IL. TGA showed that IL could effectively improve the thermal stability of PVA. The thermal stability of the PVA/IL composites decreased gradually with increasing IL content, but was higher than that of PVA. Thermal processing window (ΔT) analysis indicated that the addition of IL could significantly broaden ΔT of the PVA/IL composites, and their ΔT values first remained basically unchanged and then increased slightly with an increase of IL. In addition, MI analysis presented that the melt processability of the PVA/IL composites was not improved with the addition of IL and it was gradually improved with increasing IL content. In this work, PVA/IL composites with wide ΔT and high melt flow properties were prepared, which will lay a solid foundation for the preparation of high‐performance PVA fibers by melt spinning. © 2022 Society of Industrial Chemistry.

Effect of ionic liquid on plasticized CS-PVP-NaI based bio-polymer blend electrolytes: Structural, thermal, dielectric and ion transport properties study

The effect of imidazolium based ionic liquid (IL), 1-ethyl-3-methylimidazolium methyl sulfate [EMIM][MeSO4] on structural, thermal, dielectric and ion transport properties of Chitosan (CS)-poly(vinyl) pyrrolidone (PVP)-polyethylene glycol (PEG)-sodium iodide (NaI) based bio-polymer blend electrolyte (BPBE) films were studied using XRD, SEM, optical microscopy (OM), ATR-FTIR, TGA and impedance spectroscopic techniques. The BPBE films based on CS-PVP-PEG-NaI-IL (x = 0, 10, 20, 30, 40, 50, 60) have been prepared using solution cast method. The sample 50IL has been found to have maximum ionic conductivity ∼ 6.10 × 10-4 S/cm at 30 °C. The XRD results reveal that the BPBE films are semi-crystalline in nature and amorphousness is optimum for 50IL. ATR-FTIR analysis reveals the interaction between the functional groups of bio-polymer electrolyte with the cations/anions of IL/salt. TGA analysis shows that the BPBE films were decomposed in multi steps. Optical microscopy results show the reduction in surface roughness with increasing IL content. This result also confirmed by SEM analysis. LSV and CV measurements were carried out for knowing the electrochemical stability window (ESW). Ionic transference number (ITN) measurement shows the 50IL sample has ITN ∼ 0.98.

Study on the mechanism of hydrogen bonding interactions between poly(vinyl alcohol) and ionic liquid

AbstractThe combination of ionic liquids (ILs) with polymers have attracted mushroom attention due to their complementary advantages. Hydrogen bonding interactions is usually responsible for the final properties of the obtained polymer/IL products. In this study, the interactions between an IL 1‐(2‐hydroxyethyl)‐3‐methylimidazolium chloride ([HOEtMIM]Cl) and poly(vinyl alcohol) (PVA) have been investigated in detail by using in situ FTIR spectroscopy. In addition, two‐dimensional (2D) correlation infrared spectroscopy and perturbation correlation moving‐window two‐dimensional (PCMW2D) technique were also employed to study the microdynamics mechanism. Hydrogen bonding interactions of PVA‐IL is highly dependent on the ILs content and the temperature. Hydrogen bonds of PVA itself dominated in the system at a low ILs content of 15 wt%. However, with increasing ILs content, hydrogen bonding interactions of PVA‐ILs gradually played a major role within PVA/IL system. It was also demonstrated that hydrogen bonds between PVA and ILs interacted most strongly in the temperature range of 81–120°C.PVA/IL system is thermodynamically compatible without phase behavior, as evidenced by DMA and optical microscopy test. This research work provides a new strategy for the performance adjustment of PVA/IL materials at the theoretical level, allowing fine‐tuning of their physicochemical properties for new applications in various fields such as energy storage, sensors, and actuators.

Effect of ionic liquid on structural, thermal and electrical transport properties of PVA-PVP based polymer blend electrolyte membrane

The present paper deals with the loading effect of ionic liquid (IL), 1-ethyl-3-methylimidazolium methylsulfate [EMIM][MS] on structural and electrical transport properties of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG)- salt, sodium methyl sulfate (MeSO4Na) based polymer blend electrolyte (PBE) films. The samples were prepared using conventional solution cast method. The x-ray Diffraction (XRD) result shows that PBE films has characteristic peak with broad halo appeared in the range 2θ = 19.95° to 22.72° reveals the amorphous nature (semi-crystalline).The % degree of crystalinity (X c ) of prepared IL based PBE films were found to decreases with increasing IL content. Fourier transform infrared (FTIR) in total attenuated reflectance (ATR) mode analysis reveals the interaction between the functional groups (C=O and O–H) of polymer electrolyte with the cation, EMIM+/anion of IL/salt. Thermogravimetric analysis (TGA) shows that IL based PBE samples decomposes in multistep and Td,onset/peak value decreases with IL loading. Sample containing 30 wt%IL shows optimum dc conductivity value ∼1.5 × 10−4 S cm−1 at 30 °C with minimum activation energy ∼0.21 eV. Logσ versus 1000/T plot for all PBE sample follow the Arrhenius type thermally activated process and activation energy decreased with increasing IL content in PBE films. Frequency dependent conductivity behavior for IL based PBE film follow the Jonscher’s power law with power law exponent, n value<1 (amorphous polymeric system). AC conductivity spectra and loss tangent spectra (tanδ) with respect to IL/temperature content scalled successfully. Dielectric relaxation behavior and conductivity relaxation were analyses with respect to IL content and temperature. Mobility, total number of charge/ion density, ion diffusivity was estimated. Ionic transference number (ITN) measurement (tion ∼0.98, tele ∼0.02) reveals that ions are principal charge carriers in present system. Linear sweep voltametry (LSV) and cyclic voltamerty (CV) measurements show that 30 wt%IL containing sample has electrochemical stability window (ESW) ∼±2.7volt and Faradic oxidation reduction peaks were observed, respectively.

Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part I: Membrane Synthesis and Characterization.

In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was determined by thermogravimetric analysis (TGA). The morphology of membranes was characterized using scanning electron microscope (SEM) and interferometric optical profilometry (WLOP). SEM results evidence that upon the small addition of xGnP into the IL-dominated environment, the interaction between IL and xGnP facilitates the migration of xGnP to the surface, while suppressing the interaction between IL and Pebax®1657. Fourier transform infrared spectroscopy (FTIR) was also used to determine the polymer–IoNF interactions and the distribution of the IL in the polymer matrix. Finally, the thermodynamic properties and phase transitions (polymer–IoNF) of these functionalized membranes were studied using differential scanning calorimetry (DSC). This analysis showed a gradual decrease in the melting point of the polyamide (PA6) blocks with a decrease in the corresponding melting enthalpy and a complete disappearance of the crystallinity of the polyether (PEO) phase with increasing IL content. This evidences the high compatibility and good mixing of the polymer and the IoNF.

Effect of [EMIM][BF4] ionic liquid on the properties of ultrafiltration membranes

We employ a miscible mixture of an imidazolium based ionic liquid (IL) and dimethylformamide (DMF) as a good solvent of polyethersulfone (PES) for fabrication of membranes by nonsolvent induced phase separation (NIPS) method. The addition of IL to the cast solution changes solvent quality, which leads to variation of rheological behavior of polymer solution as well as developed membranes performance. We characterize the prepared membranes in terms of water flux, bovine serum albumin (BSA) rejection, pore size, porosity, and water contact angle. Results show that IL influences the kinetics and thermodynamic of phase separation of PES solution. Viscosity values as well as thermodynamic instability of PES solution increase with IL concentration, which lead to higher porosity and pore size of final membranes. Consequently, 17 wt% IL in formulation leads to an increase of mean pore size from 2.0 to 12.7 nm which improves water flux of final membranes from 0.5 to 77 kg/m2h. The results of fouling measurements show that by increasing IL content, the reversible fouling increases. Additionally, the irreversible fouling ratio reduces from 0.42 to 0.28 for 0 and 17 wt% IL containing formulations, respectively. The newly developed membranes provide 97% rejection of BSA solution and can be used as ultrafiltration membranes for the separation and concentration of macromolecules and proteins.

Inorganic/organic double-network ion gel membrane with a high ionic liquid content for CO2 separation

To examine the potential of ion gels as materials for CO2 separation membranes, inorganic/organic double-network ion gel (DN ion gel) membranes with different ionic liquid (IL) contents were fabricated. The composition of the inorganic and organic networks was optimized to maximize the mechanical strength of the DN ion gel. The DN ion gel with an inorganic/organic network composition of 0.35 mol/mol showed the maximum mechanical strength because the inorganic and organic networks sufficiently acted as sacrificial bonds and hidden lengths, respectively. Using DN ion gel membranes with different IL contents prepared with the optimized precursor solution, the relationship between the CO2 permeability and IL content of the DN ion gel membranes was examined. The DN ion gel membrane with 95.2 wt% IL had a CO2 permeability of 1380 barrer, which was ~67% of the theoretical maximum predicted for the pure IL membrane. The CO2 permeability of the DN ion gel membrane exponentially increased with increasing IL content and approached the theoretical maximum. DN ion gels with high strength can be used to develop maximum-performance IL-based CO2 separation membranes by giving the membrane the maximum IL potential. The effect of the ionic liquid content in tough inorganic/organic double-network (DN) ion gel membrane on the CO2 permeability was investigated. By optimizing the composition of the inorganic and organic networks, the mechanical strength of the DN ion gel was significantly increased, and the DN ion gel membrane with more than 95 wt% of an ionic liquid was successfully prepared. With the increase in the ionic liquid content, the CO2 permeability of the DN ion gel membrane exponentially increased up to ~67% of the theoretical maximum CO2 permeability.

Tailoring the Thermal and Mechanical Properties of PolyActiveTM Poly(Ether-Ester) Multiblock Copolymers Via Blending with CO2-Phylic Ionic Liquid.

The last decade has seen an exponential increase in the number of studies focused on novel applications for ionic liquids (ILs). Blends of polymers with ILs have been proposed for use in fuel cells, batteries, gas separation membranes, packaging, etc., each requiring a set of specific physico-chemical properties. In this work, blends of four grades of the poly(ether-ester) multiblock copolymer PolyActive™ with different concentrations of the CO2-philic 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf2N] were prepared in the form of dense films by a solution casting and solvent evaporation method, in view of their potential use as gas separation membranes for CO2 capture. Depending on the polymer structure, the material properties could be tailored over a wide range by means of the IL content. All samples were dry-feeling, highly elastic self-standing dense films. The microstructure of the blends was studied by scanning electron microscopy with a backscattering detector, able to observe anisotropy in the sample, while a special topographic analysis mode allowed the visualization of surface roughness. Samples with the longest poly(ethylene oxide terephthalate) (PEOT) blocks were significantly more anisotropic than those with shorter blocks, and this heterogeneity increased with increasing IL content. DSC analysis revealed a significant decrease in the melting enthalpy and melting temperature of the crystalline PEOT domains with increasing IL content, forming an amorphous phase with Tg ≈ −50 °C, whereas the polybutylene terephthalate (PBT) phase was hardly affected. This indicates better compatibility of the IL with the polyether phase than the polyester phase. Young’s modulus was highest and most IL-dependent for the sample with the highest PEOT content and PEOT block length, due to its high crystallinity. Similarly, the sample with short PEOT blocks and high PBT content also showed a high modulus and tensile strength, but much lower maximum elongation. This study provides a detailed discussion on the correlation between the morphological, thermal, and mechanical properties of these PolyActive™/[BMIM][Tf2N] blends.

Highly Sensitive Humidity Sensor Based on Ionic Liquid–Polymer Composites

Polymer composites comprising the ionic liquid (IL) [Bmim][FeCl4] and poly(vinylidene fluoride) (PVDF) have been developed for humidity sensing applications. Different IL contents (5, 10, and 20 wt %) were incorporated into the PVDF matrix and the morphological, physical–chemical and electrical properties of the composites evaluated, together with their humidity sensitivity response. Higher IL contents (20 wt %) induce a porous morphology in the composites. Further, IL incorporation leads to the crystallization of PVDF in the electroactive β phase, which content increases with the incorporation of IL into the polymer. The thermal stability of the composites decreases with increasing IL content. The humidity sensing response of the composites was evaluated with relative humidity variations from 35 to 90%. It is shown that all composites exhibit a linear resistance variation with the relative humidity, the sensitivity to humidity variations increasing linearly with the IL content. The developed materials show a strong potentiality for printable humidity sensors.

Inhibiting effects of 1-butyl-3-methyl imidazole tetrafluoroborate on coal spontaneous combustion under different oxygen concentrations

Exothermicity is a key parameter for evaluating coal spontaneous combustion (CSC). A suitable oxygen concentration is essential for CSC. Ionic liquids (ILs), which are a popular type of fire prevention material, inhibit coal oxidation. 1-Butyl-3-methyl imidazole tetrafluoroborate ([BMIM][BF4]) was used at various mass ratios (0, 2, 5, and 10 mass%) to treat coal to inhibit CSC. Through simultaneous thermal analysis tests, coal samples were investigated in atmospheres with oxygen concentrations of 5, 10, 15, and 21 vol%. The results indicated that the mass loss decreased with increasing IL content. However, the mass loss did not decrease indefinitely with increasing IL content. The lowest mass loss was observed at an IL concentration of approximately 7.5 mass%. The inhibition increased with decreasing oxygen concentrations. Moreover, the inhibiting effect first increased slowly until the IL concentration exceeded 10 mass%, after which the inhibiting effect increased rapidly. The relationship between the exothermic rate and the mass loss rate of the coal at Stage 2 of the reaction was comparatively analysed. The reaction rate between oxygen and coal was the key factor influencing the exothermic rate. In the oxidation of coal, both the oxygen concentration and inhibitor content affected the comprehensive combustion index of coal.

Conductivity and capacitance studies of silica glass composites containing [BMIM]Br and LiCl

Ionic liquid (IL) 1-butyl-3methylimidaolium bromide ([BMIM]Br) confined Li+ ion containing silica glass composites have been prepared by hydrolytic sol-gel process. The IL dispersed amorphous systems exhibit improved ionic conductivity. It has been revealed that presence of IL in a low concentration (upto 1 mol %) facilitates Li+ ion motion. Conductivity does not show any appreciable change with increasing IL content in the matrix, particularly when salt content is fixed. However, when the IL content is fixed in the matrix and salt content is gradually increased, the conductivity exhibits a monotonic rise. A maximum ionic conductivity of 4.7 × 10−7 Ω−1 cm−1 with 30 mol % LiCl and only 1 mol% IL has been observed at 523 K. Incorporation of heavy metal ions (Pb2+) in the system further enhances the conductivity marginally. Optimized compositons exhibit high capacitance values of 14.1 Fg−1 at room temperature when sandwiched between high surface area (260 m2 g−1) activated carbon electrodes. These samples exhibit good potential as solid electrolytes in solid state supercapacitor applicatons.

Ion transport mechanism and dielectric relaxation behavior of PVA-imidazolium ionic liquid-based polymer electrolytes

Solid polymer electrolytes based on poly(vinyl alcohol) (PVA) with different wt% ionic liquid (IL), 1-Butyl-2, 3-dimethylimidazolium tetraflouroborate [BDMITFB] were prepared using the solution cast technique. Prepared samples were characterized using the AC impedance spectroscopic technique. AC conductivity spectra of a PVA-IL-based system at different concentrations/temperatures have been discussed. The fitted AC conductivity spectra using Jonscher’s power law (JPL) exhibits the correlated barrier hopping (CBH) type conduction mechanism. The scaled AC conductivity spectra of PVA-IL-based films with temperature/concentrations collapsed into a single master curve indicating the ion conduction mechanism have the same origin. For higher IL loaded samples (20 and 25 wt%) mobility, μ dc conductivity, σdc as well as total number density of charge carriers, N increases with increasing IL content in PVA. Dielectric permittivity (ε′ and ε″) and electric modulus (M′ and M″) study of prepared samples has been done. Temperature-dependent dc conductivity for prepared polymeric films follows the Arrhenius type thermally activated process.

Ionic-Liquid-Based Printable Materials for Thermochromic and Thermoresistive Applications.

Smart materials exhibiting thermochromic and themoresistive properties based on the electroactive polymer poly(vinylidene fluoride) (PVDF) and the ionic liquid (IL) bis(1-butyl-3-methylimidazolium) tetrachloronickelate ([Bmim]2[NiCl4]) have been developed with different contents of [Bmim]2[NiCl4] (10, 20, and 40 wt %) within the polymer matrix. The morphology of the composites is studied, and the thermochromic and thermoresistive properties are evaluated. Independently of the IL content, the PVDF/[Bmim]2[NiCl4] composites present a porous morphology and thermochromic response, revealed by the color change of the composites from transparent to dark blue, attributed to the tetrahedral complex NiCl42- formed after a dehydration process. Further, the electrical conductivity increases with increasing IL content and decreases with increasing temperature. It is also shown that the incorporation of the IL into the PVDF matrix leads to an increase in the electroactive β phase and a decrease in the degree of crystallinity and thermal stability with increasing [Bmim]2[NiCl4] content. The printability and applicability of the developed materials as sensors are also demonstrated.

Sulfonated Polyimide/Ionic Liquid Composite Membranes for CO2 Separation: Transport Properties in Relation to Their Nanostructures

The transport properties of ionic liquid (IL)/sulfonated polyimide (SPI) composite membranes for CO2 separation were explored in relation to their nanostructures. 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C4mim][NTf2]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([P14][NTf2]) were selected as the ILs. These composite membranes enable favorable CO2 separation and superior mechanical properties. SPI is plasticized by the IL, which induces a decrease in the elastic modulus; however, due to the formation of bicontinuous nanostructures of IL-rich and SPI-rich phases, a modulus of >10 MPa is retained even with the incorporation of 75 wt % IL. [C4mim][NTf2] and [C4mim]PF6 exhibit stronger plasticization effects on SPI than [P14][NTf2]. The diffusion coefficients of CO2 and N2, which were measured by the time-lag method, abruptly increase with increasing IL content in the [C4mim][NTf2]/SPI composite memb...

An In situ Study on the Orderly Crystal Growth of Pluronic F127 Block Copolymer Blended with and without Ionic Liquid during Isothermal Crystallization

Isothermal crystallization behavior of Pluronic F127 blended with and without an ionic liquid (IL) was investigated by in situ polarized optical microscopy (POM) and Fourier transform infrared spectroscopy (FTIR). For the pure F127, the POM and FTIR results showed that the spherulite size and crystallinity of F127 increased with the melting temperature increasing to 60, 80, and 135°C. This could be explained by the flexibility of the polymer chain at high melting temperatures. For the F127 blended with IL, the POM results showed that the morphology of F127 evolved from spherulite to dendritic segregation and fibrous crystal with the increasing IL content. FTIR results indicated that hydrogen bonds were formed between F127 and IL, and the intensity of the hydrogen bonds became strengthened gradually with increasing IL content. The effect of hydrogen bonds on the morphology evolution of F127/IL is discussed.

Decoupling of segmental relaxation from ionic conductivity in [DEMM][TFSI] room temperature ionic liquid incorporated poly(vinylidenefluoride-co-hexafluoropropylene) membranes

Herein, thermophysical and electrical properties of different polymer membranes, prepared by incorporating different amounts of room temperature ionic liquid (IL), N,N-diethyl-N-(2-methacryloylethyl)-N-methylammonium bis(trifluoromethylsulfonyl) imide ([DEMM][TFSI]), in poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer, have been studied. The study reveals that [DEMM][TFSI] IL essentially reduces the crystal growth and promotes electroactive β-phase transformation within the polymer matrix by the interaction between the polymer chains and IL cations. The ionic conductivity of polymeric membranes increases with increasing IL content and attains a maximum value of 4.0×10−4S·cm−1 for highest fraction of ionic liquid (50%) at room temperature (303K). Correlation between ion transport and segmental relaxation in polymer membranes has been analyzed using dielectric spectroscopy. The analysis shows that with increasing faction of the ionic liquid the ionic conductivity gradually decouples from the segmental dynamics of the polymer. This is attributed to the higher diffusivity of relatively free anions at lower temperatures, where the segmental dynamics of polymer significantly slow down.

Development of ethanolamine‐based ionic liquid membranes for efficient CO2/CH4 separation

ABSTRACTThis study is focused on the development of ionic liquids (ILs) based polymeric membranes for the separation of carbon dioxide (CO2) from methane (CH4). The advantage of ILs in selective CO2 absorption is that it enhances the CO2 selective separation for the ionic liquid membranes (ILMs). ILMs are developed and characterized with two different ILs using the solution‐casting method. Three different blend compositions of ILs and polysulfone (PSF) are selected for each ILMs 10, 20, and 30 wt %. Effect of the different types of ILs such as triethanolamine formate (TEAF) and triethanolamine acetate (TEAA) are investigated on PSF‐based ILMs. Field emission scanning electron microscopy analysis of the membranes showed reasonable homogeneity between the ILs and PSF. Thermogravimetric analysis showed that by increasing the ILs loading thermal stability of the membranes improved. Mechanical analysis on developed membranes showed that ILs phase reduced the amount of plastic flow of the PSF phase and therefore, fracture takes place at gradually lower strains with increasing ILs content. Gas permeation evaluation was carried out on the developed membranes for CO2/CH4 separation between 2 bar to 10 bar feed pressure. Results showed that CO2 permeance increases with the addition of ILs 10–30 wt % in ILMs. With 20–30 wt % TEAF‐ILMs and TEAA‐ILMs, the highest selectivity of a CO2/CH4 53.96 ± 0.3, 37.64 ± 0.2 and CO2 permeance 69.5 ± 0.6, 55.21 ± 0.3 is observed for treated membrane at 2–10 bar. The selectivity using mixed gas test at various CO2/CH4 compositions shows consistent results with the ideal gas selectivity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45395.