Supramolecular Ionic-Liquid Gels with High Ionic Conductivity

Supramolecular ionogels were prepared by the gelation of room‐temperature ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([BMIm][BF4]) with (S,S)‐bis(leucinol)oxalamide. Remarkably, the ionic conductivity of solutions and ionogels with low gelator concentrations is higher than that of neat [BMIm][BF4]. On the basis of molecular dynamics simulations and quantum mechanical calculations, the origin of this phenomenon is attributed to the higher affinity of gelator molecules towards [BF4]− ions, which reduces the electrostatic attraction between [BMIm]+ and [BF4]− and thus increases their mobility. With increasing gelator concentration, the ionic conductivity decreases due to the formation of a denser gelator matrix, which hinders the pathways for ionic transport. However, even for very dense ionogels, this decrease is less than one order of magnitude relative to neat [BMIm][BF4], and thus they can be classified as highly conductive materials with strong potential for application as functional electrolytes. Supramolecular ionogels: The gelation of room‐temperature ionic liquid [BMIm][BF4] (BMIm=1‐butyl‐3‐methylimidazolium) by an oxalamide‐based gelator resulted in an ionogel with enhanced ionic conductivity at low gelator concentrations. The improved ion transport is a consequence of specific interactions between gelator molecules and ionic species (see figure).