Syntheses and characterisation of hydrophobic ionic liquids containing trialkyl(2-ethoxy-2-oxoethyl)ammonium or N-(1-methylpyrrolidyl-2-ethoxy-2-oxoethyl)ammonium cations

A series of salts based on ethyl ester betaine derivatives [trialkyl(2-ethoxy-2-oxoethyl)ammonium or N-(1-methylpyrrolidyl-2-ethoxy-2-oxoethyl)ammonium cations] with alkyl chains [ethyl, n-propyl and n-butyl] have been synthesized. These cations generate hydrophobic ionic liquids with bis(trifluoromethylsulfonyl)imide, tetrafluoroborate or dicyanamide anions. The influence of the alkyl chain length and the chemical nature of the counteranion on physicochemical properties such as density, melting point, glass transition and decomposition temperatures, viscosity, and electrochemical window have been investigated. [Display omitted] •Hydrophobic ionic liquids (ILs) based on ester betaine derivatives were synthesized.•The density of the ILs decreased with increasing number of carbon atoms on the organic cations.•The viscosity of the ILs depends on the nature of the anion.•These ILs revealed a wide range of the electrochemical windows.