Symmetrical 1,3-Dialkylimidazolium Based Ionic Liquid Crystals

摘要

The synthesis and characterization for a series of symmetrical 1,3-dialkylimidazolium salts with different chain lengths and counter anions together with their 1-alkylimidazole precursors are described. Liquid crystal (LC) properties of these salts are studied. Images under polarizing optical microscopy show focal conic texture together with homeotropic domains. A smectic A mesophase, typical for rod-like imida-zolium salts, is assigned. Studies from powder X-ray diffraction suggest a lamellar structure with non-interdigitated monolayer arrangement for the LC salts in the mesophase. In addition, a short note on the structure and property relationship for rod-like, disc- or fan-like, and dendritic shaped imidazolium ionic liquid crystals (ImILCs) forming smectic, columnar, and cubic phase is briefly summarized. A comparison of minimum alkyl chain length needed for l-alkyl-3-methyl and symmetrical 1,3-dialkyl ImlLCs to exhibit LC behavior is addressed.