Ether tails make a large difference for the structural dynamics of imidazolium-based ionic liquids

Anion and ether group influence in protic guanidinium ionic liquids

“…The ionic liquids with the imide-type anions were the only samples that showed clearly separated peaks, whereas the other scattering patterns show broad, merging peaks. Broader peaks than the alkylated counterparts are frequently reported for ionic liquids with ether groups [79][80][81] and are the result of the more diffuse cation-anion arrangements stemming from the charge shielding of the cation core by the more polar functional groups. 49 We fitted the peaks with Lorentzian functions for a quantitative comparison of their positions.…”

Structural Origins of Viscosity in Imidazolium and Pyrrolidinium Ionic Liquids Coupled with the NTf2– Anion

“…Equation defines S ( q , t ) − Here, ρ 0 is the total number density of the IL, x i and x j are atomic mole fractions, and the f i ( q ) and f j ( q ) functions are the corresponding X-ray atomic form factors. In all our calculations, we use a Lorch-type function, , W ( r ), to account for the fact that box sizes are not infinite, resulting in reciprocal space oscillations due to cutoff errors in the normalized distinct van Hove function, g d ij ( r , t ), at the edge of the box.…”

“…g d ij ( r , t ) is equal to 1 at long times, and at any time it goes to 1 at long distances. Just as we have done in several prior publications, S­( q ) and S ( q , t ) can be partitioned into useful subcomponents. − ,,− ,,,,− These allow us to follow the structural dynamics of liquid structural motifs at specific q values. In the Results and Discussion section, we will plot the time integral of the head–anion subcomponent of S ( q , t ) squared ( S H–A ( q , t ) 2 ).…”

“…Data on density, conductivity, viscosity, and T g are compared for all of these systems, and their structure is characterized via X-ray scattering. Simulations help us go beyond what we can measure by connecting the static structure of these ILs as well as their structural dynamics − ,− with the viscosity and viscoelastic relaxation. We will show that this exercise will help us further our chemical intuition on the concept of harder and softer ions.…”

“…Instead, correlations at shorter distance, what we call adjacency correlations, made up the second largest contribution to the viscoelastic relaxation. Given the importance that the charge network appears to have in defining viscosity and the viscoelastic relaxation, − ,, this article is set to explore differences in the static structure and its relaxation of imidazolium-based and pyrrolidinium-based ILs coupled with NTf 2 – ; the goal is to establish simple principles that explain the observed trends across these.…”