Ionic liquids (ILs) have low melting temperatures (< 100°C) due to their weak ionic interaction between bulky organic cations and inorganic anions. From their novel properties such as wide range of reactivity (from hydrophilic to hydrophobic), non-flammability, and very low volatility (<10-10 Pa at 25oC), ILs have been explosively studied as a future green solvent. In addition, they exhibit high ionic conductivity (10-3 S/cm) and thermal stability (decomposition temperature ~ 400°C). Consequently, ILs have been studied as substitutes for electrolytes in green energy fields. Safety and environmental pollution are serious issues for future electrolytes, Solid-state electrolytes have been spotlighted for such applications and self-assembly is an ideal supramolecular process which has little energy consumption. If we consider the fuel-cell electrolyte, aggregation in anhydrous system is an important issue as well.
Recently, we made an rod-shape self-assembled single crystals by mixing octanol and 1-tetradecyl-3-methylimidazolium chloride ([C14MIM]Cl) IL into the alkane solvent. Observed maximum length was 5.2 mm. But the crystalline structure was broken by small amount of water, and the system showed up single phase w/o (water-in-oil) microemulsion with increasing the water concentration. To analyze two different systems, we used X-ray diffraction (XRD), Small Angle Neutron Scattering (SANS), and 1H NMR techniques. In addition, we studied the fundamental mechanism of destruction and reconstruction to realize the self-assembled crystal with short chain ILs. [C2MIM]TFSI IL is well known as having high ionic conductivity.
