Thermochimica Acta, Vol.664, 81-90, 2018
Measurements of the density, refractive index, electrical conductivity, thermal conductivity and dynamic viscosity for tributylmethylphosphonium and methylsulfate based ionic liquids
In this work, the effect of ion and temperature change on the thermophysical properties of several ionic liquids was investigated. Five room-temperature ionic-liquids were selected: tributylmethylphosphonium chloride ([P-4441]Cl), tributylmethylphosphonium bis(trifluoromethylsulfonyl) amide ([P-4441][NTf2]), tributylmethylphosphonium methylsulfate ([P-4441][MeSO4]), 1-methylpyridinium methylsulfate ([C-1py][MeSO4]), and 1butyl-3-methylimidazolium methylsulfate ([C(4)mim] [MeSO4]). Densities, refractive indices, electrical conductivities, thermal conductivities and dynamic viscosities were reported ranging from (283.15 to 343.15) K at atmospheric pressure. The thermal stability of all the ionic liquids has been also studied at a heating rate of 5 K min(-1) using a thermogravimetric analyzer. The effect of temperature change on density was discussed in terms of ion volume, and the influence on electrical conductivity and dynamic viscosity was discussed in terms of ion mobility. The effect of the variation of the ion was discussed in terms of size, steric effects and interaction strength between cation and anion. Finally, the temperature dependence for density, refractive index and thermal conductivity was correlated with linear functions, while a Vogel-Fulcher-Tammann type function was used for the correlation of the temperature dependence for electrical conductivity and dynamic viscosity.