SYNTHESIS AND THERMOPHYSICAL CHARACTERIZATION OF TRIOCTYLTETRADECYLPHOSPHONIUM-BASED ROOM TEMPERATURE IONIC LIQUIDS

Room temperature ionic liquids (RTILs) based on trioctyltetradecylphosphonium
[P8,8,8,14] with chloride [Cl] and dioctylsulfosuccinate [docusate] anions were prepared
and characterized using 1H NMR and elemental analysis. The experimental values of
density and dynamic viscosity at a temperature range (293.15 to 353.15) K and refractive
index (298.15 to 343.15) K were measured at atmospheric pressure. The measured
density, viscosity and refractive index of the present ionic liquids; [P8,8,8,14]Cl and
[P8,8,8,14][docusate] at 298.15 K are (0.8858 and 0.9544) g.cm-3, ( 1272.2 and 2960.3)
mPa.s and (1.47832 and 1.46934) respectively. The density of the present IL is lower
compared to the phosphonium ILs with short alkyl chain due to the increases free volume
of the longer alkyl chain. The results show that these ILs possesses higher viscosities and
similar refractive indices compared to the trihexyltetradecylphosphonium ILs.
Experimental values of density and refractive index are used to estimate the thermal
expansion coefficients and crystal energy.