Apparent molar volume at infinite dilution, expansivities and electrochemical behaviours of binary system (tetramethylpiperidine 1-oxyl-based ionic liquids + water)

At T = (278.15–318.15) K and atmospheric pressure, Hepler’s constant values, (∂2VB/∂ T2)P, and apparent molar expansivities (Eφ) were calculated using the temperature dependence of apparent molar volumes (VB). Because of the increase in hydrophobic hydration of tetramethylpiperidine 1-oxyl-based ionic liquids (TILs), the Hepler’s constant values were found to change from positive to negative, indicating that the TILs under consideration changed primarily from structure-promoting to structure-breaking. The critical micelle concentration of conductivity (CMC) was calculated based on experimental conductivity, which reflects the dissociation and the interaction and aggregation behaviour of TILs.