In this study, a series of nitrile-functionalised imidazolium ionic liquids (C 2CN RimCl, where R = butyl, hexyl and octyl) were synthesised by reacting imidazole with acrylonitrile and then with butyl, hexyl and octyl chlorides, respectively. The structure of these compounds were established using 1H NMR, FT-IR and elemental analyses. The densities and viscosities were measured at T = (293.15-353.15 K), whereas the refractive index was measured at T = (293.15-333.15 K) and empirical correlations were proposed to represent this study. The decomposition temperatures were determined using a thermogravimetric analyser. The thermal expansion coefficients were also calculated and reported. © 2012 Copyright Taylor and Francis Group, LLC.