Effect of gelator structures on electrochemical properties of ionic-liquid supramolecular gel electrolytes

Bis(4-acylaminophenyl)methane (G1) and bis(4-acylaminophenyl)ether (G2) with varied acyl chains were found to be efficient gelators for the gelation of imidazole-based ionic liquids. The supramolecular gel electrolytes were formed via the self-assembly of these gelators in ionic liquids. The minimum gelator concentrations (MGCs) for the gelation of ionic liquids depend on the chemical structures of the gelators. The longer the acyl chains, the lower the MGCs. Polarized optical microscopy images of the ionic-liquid gels reveal the formation of spherical crystallites resulting from the fibrillar aggregates of the gelators. In addition, the phase transition temperatures of the ionic-liquid gels increase with an increase of the acyl chain length of the gelators. The impedance spectra of the ionic-liquid gels indicate that the temperature dependence of the conductivity follows the classical Arrhenius equation. The conductivities of ionic-liquid gels also decrease with an increase of the acyl chain length, but the differences in conductivities between the gels and corresponding ionic liquids are in one order of magnitude. The ionic-liquid gels possess a stable electrochemical window.