Symmetrical 1,3-Dialkylimidazolium Based Ionic Liquid Crystals

• Published in: Journal of the Chinese Chemical Society (Taipei) Vol. 60; no. 7; pp. 745 - 754
• Main Authors: Rohini, Rondla, Lee, Ching-Kuan, Lu, Jung-Tang, Lin, Ivan J. B.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.07.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: 1,3‐Dialkylimidazolium salts; 1-Alkylimidazoles; 3-Dialkylimidazolium salts; Ions; Liquid crystal property; Microstructure; Synthesis
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.201200598

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 imidazolium salts, is assigned. Studies from powder X‐ray diffraction suggest a lamellar structure with noninterdigitated 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 1‐alkyl‐3‐methyl and symmetrical 1,3‐dialkyl ImILCs to exhibit LC behavior is addressed. Synthesis and characterization for series of symmetrical 1,3‐dialkylimidazolium salts and their 1‐alkylimidazole precursors are presented. The LC properties of symmetrical 1,3‐dialkyl ImILCs with different counter anions (Cl−, Br−, I−, PF6−) are described. A smectic A mesophase, typical for rod‐like imidazolium salts, is assigned.