The thermophysical properties of 1-alkylpyridinium bis(trifluoromethylsulfonyl)imide, [C(n)py][Tf2N] ionic liquids where n = 4, 8, 10, or 12 have been determined. Density rho, and dynamic viscosity eta, were determined at T = (293.15 to 353.15) K and refractive index n(D), was measured at T = (293.15 to 333.15) K. Empirical correlations are proposed to represent the present experimental results, The values of the coefficient of thermal expansion were calculated from the experimental density Values. The thermal decomposition temperature, T-d was also determined using thermogravimetric analyzer (TGA) at a heating rate of (10 and 20) K . min(-1). (C) 2009 Elsevier Ltd. All rights reserved.