Synthesis of Novel Chiral Ionic Liquids and Their Phase Behavior in Mixtures with Smectic and Nematic Liquid Crystals

Alkylation of 1‐alkyl‐1H‐imidazoles 2a–f with citronellyl bromide 1b opens access to chiral 1H‐imidazolium bromides 3a–f (Scheme 1). A similar strategy yielded the chiral pyridinium ionic liquid 6 (Scheme 2). Dialkylation of 1H‐imidazole (7) gave the C2‐symmetric 1,3‐dicitronellyl‐1H‐imidazolium bromide (8) (Scheme 3). Differential scanning calorimetry and optical polarizing microscopy revealed smectic mesophases for 1‐citronellyl‐3‐tetradecy‐1H‐limidazolium bromide (3e) and 1‐citronellylpyridinium bromide (6) (Table). In binary mixtures with smectic and nematic liquid crystals 9 and 10, 1‐citronellyl‐3‐methyl‐1H‐imidazolium bromide (3a) behaved differently. Increasing quantities of 3a cause a decrease of the smectic‐phase width for the mixture 3a/9 (Fig. 3), whereas the phase width of the nematic phase for 3a/10 remained nearly constant (Fig. 4).