Ester-Containing Imidazolium-Type Ionic Liquid Crystals Derived from Bio-based Fatty Alcohols

The need to take into account the life cycle of ionic liquids (ILs), from sourcing raw materials involved in their synthesis disposal and degradation, has become paramount design new IL-type molecular structures. In case 1-alkyl-3-methylimidazolium salts, one prominent IL families, there is an increasing demand for synthetic methods involving (i) substitution petro-based alkyl derivatives by readily available bio-sourced surrogates (ii) functionalization tail with heterofunctional groups enabling (bio)degradation ILs after use. Herein, a straightforward industrially viable lipidic imidazolium salts reported, starting different fatty alcohols, including oleic, stearyl, lauryl alcohols. This procedure based on acrylation followed aza-Michael addition imidazole group onto acrylate moiety. Subsequent quaternization, using either methyl iodide or tosylate, provides library 1-alkylpropionate-3-methylimidazolium various chain lengths (C18, C12, C11) incorporating types counteranions (iodide, tetrafluoroborate). These ester-containing analogues classical are all ILs, that is, melting point below 100 °C. addition, most them exhibit liquid-crystal behavior can be referred as crystals (ILCs). thermal stability, well phase transitions these been investigated thermogravimetric analysis, differential scanning calorimetry, respectively, while structure crystalline mesophase studied X-ray scattering. Interestingly, ILCs featuring unsaturated tails low point, close room temperature, presence ester function shown provide enhanced stabilization mesophase.