Density, Viscosity, and Electrical Conductivity of 1-Alkyl-3-methylimidazolium Dicyanamide Ionic Liquids

Abstract

A series of 1-alkyl-3-methylimidazolium dicyanamide ionic liquids ([C n mim]­[N­(CN)2], n = 2, 3, 4, 5, and 6) were synthesized and characterized in this work. The density, viscosity, and electrical conductivity of these ionic liquids were measured from 293.15 to 353.15 K at 101.3 kPa using a high-precision vibrating tube density meter, an automated falling ball viscometer, and a conductivity meter, respectively. On this basis, the corresponding molar volume and molar conductivity were also obtained. All experimental values were well-fitted by the empirical equations. Remarkably, these ionic liquids exhibit much lower density, lower viscosity, and higher electrical conductivity than many other conventional ionic liquids. According to the theoretical calculations, the weaker cation–anion interaction and V-shaped and nonspherical structure of the dicyanamide anion are considered as major reasons for these properties. Meanwhile, the extension of the alkyl side chain length can result in lower density, higher molar volume, higher viscosity, and lower conductivity. This phenomenon is probably ascribed to the decreasing molecular symmetry, enhanced hydrogen bonding, and increasing steric hindrance of ionic liquids. The relationship between viscosity and molar conductivity has been also investigated using the Walden rule, which confirms the high ionicity of [C n mim]­[N­(CN)2]. The enhanced dissociation of ions may favor the ionic fluidity and conductivity. It is hoped that these experimental results and theoretical findings may be useful for the future development of dicyanamide-based ionic liquids.

Experimental and DFT Studies on Electrochemical Performances of Ester-Containing Vinylimidazolium Ionic Liquids: Effect of the Ester Substituent and Anion

“…At the same temperatures, the electrical conductivity values decrease with the increase of the alkyl chain length of the ester group in imidazolium cations from ethyl to butyl. This phenomenon agrees with refs − .…”

Ionic Liquid-Based Electrolytes for Aluminum/Magnesium/Sodium-Ion Batteries

“…The anions can be halogens, like Cl -(most used in AIBs), Br -, I -, or organic anions. Then, the general ionic liquid electrolytes for AIBs can be obtained by mixing the ionic liquid and AlCl 3 [33][34][35][36][37][38]. Volumetric capacity (Ah L −1 ) Earth crust abundance (wt%)…”

Environmentally friendly ionic liquid medium based on dicyanamide anion for leaching gold from e‐waste CPUs by iodination

“…35 The viscosities of ILs depend on the size of the ions, bonding, and space available for the solvent molecules or ions to move into. 36 Low-viscosity ILs based on dicyandiamide anions were first reported by MacFarlane et al in 2001. 37 Their test showed that the viscosity of 1-ethyl-3-methylimidazolium dicyanamide (([C 2 MIM] [N(CN) 2 ) was only 21 cP at 25 °C, which is significantly lower than that of most ILs.…”

“…However, most DESs have relatively high viscosities, in a range above 100 cp at 25 °C, which limits solvation, filtration, and heat transfer, and makes them unsuitable in large‐scale applications 35 . The viscosities of ILs depend on the size of the ions, bonding, and space available for the solvent molecules or ions to move into 36 . Low‐viscosity ILs based on dicyandiamide anions were first reported by MacFarlane et al .…”