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

Alkylation of 1‐alkyl‐1 H ‐imidazoles 2a – f with citronellyl bromide 1b opens access to chiral 1 H ‐imidazolium bromides 3a – f ( Scheme 1 ). A similar strategy yielded the chiral pyridinium ionic liquid 6 ( Scheme 2 ). Dialkylation of 1 H ‐imidazole ( 7 ) gave the C 2 ‐symmetric 1,3‐dicitronellyl‐1 H ‐imidazolium bromide ( 8 ) ( Scheme 3 ). Differential scanning calorimetry and optical polarizing microscopy revealed smectic mesophases for 1‐citronellyl‐3‐tetradecy‐1 H ‐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‐1 H ‐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 ).