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Abstract: The coordination states of the divalent and trivalent rare earth complexes in ionic liquid, triethyl-pentyl-phosphonium bis(trifluoromethyl-sulfonyl) amide [P2225][TFSA] were investigated by Raman spectroscopy and DFT calculation. The concentration dependences of the deconvoluted Raman spectra were investigated for 0.23–0.45 mol kg-1 RE(III), RE=Nd and Dy, and the mixed sample of RE(II)/RE(III)=1/3 at the molar ratio in [P2225][TFSA]. According to the conventional analysis, the solvation number; n of rare earth complexes in [P2225][TFSA] were determined to be n=4.06 for Nd(II), 5.01 for Nd(III), 4.12 for Dy(II) and 5.00 for Dy(III). Thermodynamic properties such as ΔisoG, ΔisoH and ΔisoS for the isomerism of [TFSA]- from trans- to cis-isomer in bulk and the first solvation sphere of the centered [RE3+] cation in [P2225][TFSA] were evaluated from the temperature dependence in the range of 298-398K. ΔisoG(bulk), ΔisoH(bulk) and TΔisoS(bulk) at 298 K were -1.06, 6.86, and 7.92 kJ mol-1, respectively. The trans-[TFSA]-was dominant in the enthalpy due to the positive value of ΔisoH(bulk) and TΔisoS(bulk) was slightly larger than ΔisoH(bulk), so that cis-[TFSA]-was revealed to be an entropy-controlled in [P2225][TFSA]. On the other hand, in the first solvation sphere of [RE3+] cation, ΔisoH (Nd)(-47.39 kJ mol-1) increased to the negative value remarkably and implied that the cis-[TFSA]- isomers were stabilized for enthalpy. ΔisoH(Nd) contributed to the remarkable decrease in the ΔisoG(Nd) and this result clearly indicated that the cis-[TFSA]- bound to Nd3+ cation was preferred and the coordination state of [Dy(III)(cis-TFSA)5]2- was stable in [P2225][TFSA] The optimized geometries and the bonding energies of [RE(II)(cis-TFSA)4]2- and [RE(III)(cis-TFSA)5]2- clusters were also investigated from DFT calculation with ADF package. The bonding energy; ΔEb was calculated from ΔEb= Etot(cluster) –Etot(RE2,3+) –nEtot([TFSA]-). ΔEb([Nd(II)(cis-TFSA)4]2-), ΔEb([Nd(III)(cis-TFSA)5]2-), ΔEb([Dy(II)(cis-TFSA)4]2-) and ΔEb([Dy(III)(cis-TFSA)5]2-) were -2241.6, -4362.3, -2135.4 and -4284.2 kJmol-1, respectively. This result was revealed that [RE(III)(cis-TFSA)5]2-cluster formed stronger coordination bonds than [Dy(II)(cis-TFSA)4]2- cluster. The average atomic charges and the bond distances of these clusters were consistent with the thermodynamic properties. Keywords: Coordination state, DFT calculation, Rare earth, Raman spectroscopy, Thermodynamic property.Download Full Article |
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Abstract: Ionic liquid-crystalline materials (ILCMs) with ammonium ions were synthesized. Their thermal and orientational properties were studied by polarizing microscopy, differential scanning calorimetry, and X-ray diffraction (XRD). The ILCMs formed the smectic A phase on heating and cooling. A focal conic fan texture was observed in the phase. In addition, the ILCMs spontaneously formed a perpendicular alignment in the smectic A phase. The XRD patterns of the ILCMs consisted of sharp reflections in the small-angle region and broad band in the wide-angle region in the smectic A phase. Keywords: Anisotropic Fluid, Ionic Liquid Crystal, Thermal Stability, X-ray diffraction. |
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Abstract: In this study the removal of methylene blue (MB) dye from aqueous solutions by polyacrylamide (PAA) as a potential adsorbent was reported. PAA was characterized using SEM and FTIR measurements. Batch adsorption experiments were performed as a function of the solution pH, contact time, solute concentration and temperature. Evaluation of the obtained data with isotherm studies indicated that the adsorption process was matched well with the Langmuir model. The maximum capacity of adsorbent for MB was 111.1 mg g−1. Kinetic studies were carried out on various kinetic models and the pseudo-second order kinetic model was fitted very well with experimental data. Moreover, the thermodynamic parameters indicated that the adsorption reaction was endothermic and spontaneous process. Keywords: Polyacrylamide,Removal,Methylene blue, Isotherm, Kinetic.Download Full Article |
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Abstract: Ionic mesogens (HI-n), constructed from imidazolium-functionalized azobenzenes with differential flexible spacers and a nitro polar terminal group, were synthesized. Their potential thermotropic liquid crystal properties were investigated bypolarizing optical microscopy (POM), differential scanning calorimetry (DSC) and temperature variable X-ray diffraction measurements. HI-n exhibited a smectic A fluid (SmA) phase by anisotropy through interactions between azobenzene units and ionic interactions. This SmA formation was observed by POM and DSC. In the SmA phase, focal conic fan textures were observed by POM under the crossed-Nicols. The perpendicular structure (homeotropic alignment) formed spontaneously in the SmA phase through physical adsorption of imidazolium ionic units upon a glass plate. In the SmA phase, HI-n exhibited the X-ray diffraction patterns consisting of sharp inner reflections, corresponding to the layer distance, and a broad outer reflection exhibiting a short range order within the smectic layer. It is expected that the SmA layer consists of the hydrophilic and hydrophobic sublayers. The hydrophilic sublayer was formed by an ionic aggregation of imidazolium and iodide ions. On the other hand, the hydrophobic sublayer was obtained by segregation from the hydrophilic sublayer. It can be considered that HI-n are an anisotropic ionic liquid because the SmA state has a fluidity such as an ionic liquid. The ionic material shows the strong temperature dependence of an ionic interaction. The ionic interactions in the liquid crystal phase became weak gradually with increasing temperature, and the fluidity of the liquid crystal phase increase. HI-n dissolved in water. The HI-n water solution revealed a lyotropic smectic A anisotropic fluid. Keywords: Anisotropic Fluid, Ionic Liquid Core, Ionic Liquid Crystal, Thermal Property, X-ray diffraction.Download Full Article |
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Abstract: The principal aim of this work is to study azeotropy breaking in the refrigerant blends with ionic liquids (IL). The global phase diagram approach is applied to correlate azeotropic data for binary mixtures based only on critical properties and acentric factor of the individual components in mixtures. Analytical expressions to predict azeotropy phenomena in terms of critical parameters of pure components and binary interaction parameters are given. The eventual azeotropy appearance in the refrigerant – IL blends is discussed and conclusion about highly improbable azeotropic blend formation for these systems is given. Global phase behavior of ionic liquid – industrial refrigerant blends is analyzed and possible III, IV and/or V types according to the classification scheme of Scott and van Konynenburg[1] are established. The azeotropy breaking in binary refrigerant mixtures with ionic liquid adding is predicted. Keywords: Phase equilibria, azeotropy breaking, ionic liquids, refrigerant blends.Download Full Article |