Ether-functionalized
ionic liquids (ILs) 1-(4-methoxybutyl)-3-methylimidazolium
chloride ([COC4mim][Cl]) and 1-(4-methoxybutyl)-3-methylimidazolium
aspartic acid ([COC4mim][Asp]) were successfully prepared.
In terms of the standard addition method, the experimental values
of the surface tension, density, and refractive index of these ether-functionalized
ILs were obtained at 288.15–318.15 K. Using the Lorentz–Lorenz
empirical equation, the values of the molar refraction and molar polarizability
for [COC4mim][Cl] and [COC4mim][Asp] ILs were
calculated. According to the definition of the polarity coefficient,
the polarity of samples and other ILs was estimated. For the same
anion, the polarity of the same series of ILs gradually reduced with
increasing carbon chain length of ILs. For the same cation, the polarity
of ILs was also influenced by anionic species. The prediction result
of the polarity coefficient was in good agreement with δμ.