3-Hexadecylimidazolium bromide was synthesized and characterized showing formation of thermotropic smectic liquid crystals at temperatures above its melting point from 48.5 to 150.9 degrees C. With decreasing temperature, the peak intensities in XRD patterns increase and full widths at half-maximum decrease, suggesting structural order increases with decreasing temperature. Compared with 1,2dimethyl-3-hexadecyl-imidazolium bromide and hexafluorophosphate, the IL shows a lower melting point and less degree of chain interdigitation. The main reason is due to a more symmetrical structure and denser assembly of the IL molecules, which results in more steric resistance for the alkyl chain to interdigitate. The self-assembly behavior of the hydrophobic IL in an organic solvent was investigated showing SmA(2) lyotropic liquid crystalline phases. The first-order scattering peak shifts to lower q values with increasing IL content, which is opposite to the shift directions of the binary mixtures of the soluble imidazolium IL and water, indicating a different packing behavior of the hydrophobic IL in 1-decanol. (C) 2011 Elsevier Inc. All rights reserved.