Physicochemical Properties and Structures of Room Temperature Ionic Liquids. 2. Variation of Alkyl Chain Length in Imidazolium Cation

The alkyl chain length of 1-alkyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide ([Rmim][(CF(3)SO(2))(2)N], R = methyl (m), ethyl (e), butyl (b), hexyl (C(6)), and octyl (C(8))) was varied to prepare a series of room-temperature ionic liquids (RTILs), and the thermal behavior, density, viscosity, self-diffusion coefficients of the cation and anion, and ionic conductivity were measured over a wide temperature range. The self-diffusion coefficient, viscosity, ionic conductivity, and molar conductivity change with temperature following the Vogel-Fulcher-Tamman equation, and the density shows a linear decrease. The pulsed-field-gradient spin-echo NMR method reveals a higher self-diffusion coefficient for…