Electrochemical and physicochemical characterizations of butylsulfate-based ionic liquids

A series of butylsulfate-based ionic liquids (ILs) are prepared using butylsulfate anions with various cations, the influences of ring structural variations of cations on their thermal property, electrochemical window, density, viscosity, and ionic conductivity are investigated. Good electrochemical stability (ca. 4.7 V) of the butylsulfate-based ILs is confirmed by voltammetric measurements, and the incorporation of methyl group to replace acidic C-2 hydrogen atom of imidazolium cation or replace imidazolium unit by pyrrolidinium or tri(n-propyl)ammonium slightly increases the cathodic stability. The deviations between ILs and ideal KCl line in adjust Walden plot decreases significantly than those in general Walden plot owing to the adjusted Walden plot takes the difference of ion size into account.