Dielectric properties of a bisimidazolium salt with dodecyl sulfate anion doped with carbon nanotubes

Abstract

A new bisimidazolium salt with dodecyl sulfate as counterion has been designed and prepared. This salt shows a SmA phase that is stable at room temperature. The new ionic liquid crystal (ILC) was characterized by 1H NMR, 13C NMR and IR spectroscopy. Its liquid crystalline properties were analyzed by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD) studies. The dielectric spectra of the ILC doped with different concentrations of carbon nanotubes (CNT) were recorded over a wide frequency and temperature range of 10−1 to 107 Hz and 293–338 K, respectively. The values of the activation energy were found in the range of 0.46–0.61 eV; the characteristic time was obtained by fitting the spectra of the dielectric loss with the Havriliak–Negami functions. As a result of doping the ILC with CNT, the electric conductivity increases significantly. Ionic conductivity is dominant and it was indirectly observed through the electrode polarization (EP) effect. The very high dielectric permittivity values and the decrease of the electric conductivity at low frequencies confirm the presence of EP.

Ionic liquid crystals: Synthesis and characterization via NMR, DSC, POM, X-ray diffraction and ionic conductivity of asymmetric viologen bistriflimide salts

“…Cherian et al [89] have very recently reported parallel conductivities of 10 - hydrogen sulfate. These values are like those shown here, and are superior to some state-of-theart polymerized ionic liquid electrolytes [90], and comparable to phosphonium or imidazoliumbased ionic liquids (10 -2 S cm -1 , at 30 o C) and to dicationic imidazolium salts forming SmA phases (10 -6 to 10 -4 S cm -1 , near room temperature) [91][92][93].…”

Ion conformation and orientational order in a dicationic ionic liquid crystal studied by solid-state nuclear magnetic resonance spectroscopy

“…In several reports on this and analogous materials, the layered mesophases were assigned as smectic A 6,[8][9][10] . We note that in work Yang et al 7 the mesophase of C 6 (C 12 im) 2 Br 2 was designated as smectic C phase, but it probably concerns smectic A phase as reported by Bara et al 6 The mesophase assignment as smectic C phase in this material was questioned in the review 1 .…”

“…There are several types such as ammonium, imidazolium, pyridinium based ILCs reported, among these monocationic imidazolium-based salts are the most studied ones 4 . Recently, dicationic ionic liquid crystals (DILCs) have also been presented [5][6][7][8][9][10][11] . DILCs are composed of a dication containing two single-charged ions covalently linked by a spacer, and single-charged anions 5 .…”

“…Increased possibilities for cation and anion combinations, presence of more than one polar and apolar units, and variation in the length and type of spacer group between charged units in dicationic ILCs is beneficial to achieve more variability and tunability of the properties of ionic liquid crystals. Imidazolium-based dicationic ILCs combined with a range of anions have been synthesized and their mesophase behavior has been studied depending on linker type and side-chain length [6][7][8][9][10] . Bipyridinium based DILCs salt have also been reported 11 .…”

High Ionic Conductivities of Ionic Materials as Potential Electrolytes

“…Whilst having alkyl terminations still fall some orders of magnitude below those exhibited by reference phosphonium or imidazolium-based ionic liquid electrolytes (10 −2 S•cm −1 ) [60,61], we found that the presence of oxyethylene groups promotes high conductivities in the 10 −1.5 S•cm −1 range, comparable to those required in commercial batteries or fuel cells [48,49]. The presence of additional polar sites in these terminations may be the key to facilitate long-range transport in these materials.…”