Development of low viscous ionic liquids: the dependence of the viscosity on the mass of the ions

Abstract

Straightforward syntheses of selected nondeuterated, partially deuterated, and fully deuterated room temperature ionic liquids (ILs) with the anions tris(pentafluoroethyl)trifluorophosphate, tetracyanoborate, and methyl sulfate were developed. The viscosity and the density of these ionic liquids were measured at various temperatures. The dissociation rate of the ionic liquid, the sizes of the cation and the anion, and the nature of the inter-ionic interaction are not influenced by deuteration, but viscosity is. All deuterated ionic liquids possess a higher viscosity and density in comparison to non-deuterated ones. The explanation of this phenomenon is given and discussed based on the modified Stokes-Einstein equation with a parameter which reflects the mass of the diffused particles. This new knowledge supports the recent development of novel low viscous inert ionic liquids which are of particular interest for the application in energy conversion devices. Deuterated ionic liquids are valuable media for the investigation of chemical reactions, natural products, and bio-materials by means of the NMR spectroscopy.

Cyanohydridoborate Anions: Synthesis, Salts, and Low‐Viscosity Ionic Liquids

“…Presumably, the low viscosity of the ILs with the borate anions [BH n (CN) 4− n ] − or [BF n (CN) 4− n ] − ( n= 1–2) compared to ILs with [B X 4 ] − ( X =CN, F) relates to less symmetrical mixed‐substituted anions. The low molecular mass of the cyanohydridoborate‐ILs compared to the respective cyanofluoroborate‐ILs is most likely the reason for their exceptional low viscosity. This is further confirmed by even higher viscosities of the chlorocyanoborate‐ILs [EMIm][BCl n (CN) 4− n ] compared to [EMIm][BF n (CN) 4− n ].…”

“…relates to less symmetrical mixed-substituted anions. The low molecular mass [37] of the cyanohydridoborate-ILsc ompared to the respective cyanofluoroborate-ILs is most likely the reason for their exceptional low viscosity.T his is further confirmed by even higherv iscosities of the chlorocyanoborate-ILs [EMIm] [BCl n (CN) 4Àn ] [40]…”

Perfluoroalkyltricyanoborate and Perfluoroalkylcyanofluoroborate Anions: Building Blocks for Low‐Viscosity Ionic Liquids

“…The difference between the trifluoromethylborate and the related pentafluoroethylborate is small, in general, but it increases with an increasing number of cyano groups (Figure ). The higher viscosities for anions with longer perfluoroalkyl chains may be explained by stronger van der Waals interactions and the higher mass of the anions . The exception discussed for [EMIm] 1 a and [EMIm] 2 a reflects the strong gain in charge delocalisation of a C 2 F 5 versus a CF 3 group.…”

Study on Gas Permeation and CO2 Separation through Ionic Liquid-Based Membranes with Siloxane-Functionalized Cations

“…[17][18][19][20] In particular, and concerning the use of specific functional groups, Niedermeyer et al 21 focused on the effect of introducing a siloxane group in the imidazolium cation on the viscosity. It was found that in spite of the increment in the cation´s mass, the viscosity of [(SiOSi)C 1 Within the context of IL-based membranes for CO 2 separation, and despite the large array of different SILM systems developed during the last decade, 6,7,23 the gas permeation properties of SILMs with siloxane-functionalized cations have still not been entirely studied and discussed.…”