Ether functionalisation, ion conformation and the optimisation of macroscopic properties in ionic liquids

Abstract

Ionic liquids are an attractive material class due to their wide liquid range, intrinsic ionic conductivity, and high chemical as well as electrochemical stability. However, the widespread use of ionic...

Structure-Property Relation of Trimethyl Ammonium Ionic Liquids for Battery Applications

“…Factors governing the viscosity of the cation and anion are not independent of each other as seen by the difference in viscosity for the alkyl and ether substituted cation when exchanging the anion. Similar findings related to a coupling of cation and anion factors affecting the transport properties of ionic liquids are also found in other studies [37]. Lower viscosities for the liquids based on the [FSI] − anion than for ones based on [TFSI] − are a general finding [40] and might be attributed to the smaller ion size or the stronger interaction of the latter with the cation, as it was shown in the literature for the [C 2 C 1 im] + cation [43].…”

“…between the ether and alkyl samples can be rationalized by a change in the cation conformation as the difference between the weight of the methylene group and the oxygen is too small to account for these relatively large differences. Change in cation conformations from a linear side chain arrangement of the alkyl groups to a kinked one for ether-cations with curling of the side chain around the cation is well known in the literature [37,42]. All temperature-dependent densities showed a linear behavior within the investigated -range.…”

“…The ionic liquids and mixture show no clear trend in the melting transition with the chosen anion, side chain length and functionalization, which is contrary to the situation found for transport properties (shown below). For instance, a common finding for ionic liquids with multiple ether substituents are significantly reduced melting temperatures and often occurrence of only glass transition when compared to the alkylated analogues [36,37]. The only overall tendency for the thermal transitions is that the mixtures of IL with 0.25 M lithium salt show lower melting and crystallization temperatures.…”

“…The underlying cause for the significantly lowered viscosity of the ether-substituted ionic liquids is the change in the cation conformation. While the side-chains of alkylated ionic liquids usually obtain linear conformation, the ether-groups are kinked and coordinate the positively charged part of the cation [37,42,46]. The origin for this curled structure is thought to be in the formation of intramolecular hydrogen bonding to the hydrogens in α-position to the cation center [47].…”

A review on machine learning algorithms for the ionic liquid chemical space

“…They trained an ANN using their MCI as input (see subsection ILs as input data) and testing the result in 26 ILsmostly based on the imidazolium cation family. The results were satisfactory, leading to general deviations less than 5% of the experimental ‡ We tested the deviation of the published library's prediction to experimental results on two ILs recently published from our group, 284…”