Ionic liquid crystals based on mesitylene-containing bis- and trisimidazolium salts

The synthesis of novel ionic liquid crystals (ILCs) based on bis- and trisimidazolium salts (I-, BF4-, and [N(SO2CF3)2]-) bearing hydrophobic hexadecyl chains and a bridging mesitylene moiety is reported. The study of their mesomorphic properties is presented, including the characterization of the Smectic A phase by differential scanning calorimetry and polarized optical microscopy. A detailed powder X-ray diffraction (p-XRD) study as a function of temperature confirmed that cooling gives rise to a glass transition from the liquid-crystalline smectic A phase to a metastable lamellar phase. In addition, in the case of bisimidazolium iodide, the ability of these molecules to form self-aggregates in solution has been demonstrated by diffusion nuclear magnetic resonance (NMR) experiments.