Structure and Aggregation in the 1-Alkyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquid Homologous Series

Abstract

A new comprehensive Molecular Dynamics study using large simulation boxes has been performed in order to complete and extend the structural analysis on the mesoscopic segregation observed in the ionic liquids of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide homologous series, [CnC1im][Ntf2] (2 ≤ n ≤ 10). The analysis includes the discussion along the whole family of the corresponding structure factors, S(q), in the low-q range (1.6 ≤ q/nm(-1) ≤ 20); the confirmation of the periodicity of the polar network of the ionic liquid and its intermediate low-q peak equivalence; and the introduction of five statistical functions that probe the existence and characterize the polar network and the nonpolar aggregates that are formed along the [CnC1im][Ntf2] series. The later functions comprise aggregate size distributions, average number of contact neighbors within an aggregate, neighbor distributions, distributions of aggregate maximum length, and distributions of aggregate volume.

Exploring the bulk-phase structure of ionic liquid mixtures using small-angle neutron scattering

“…The data in this range of compositions are dominated by a large PNPP, which is characteristic of the scattering seen in nano-structured pure ILs such as [C 12mim] [Tf2N]. 36 The position of the PNPP shifts steadily to higher q between x = 0.52 (where it is at 1.8 nm -1 ) and x = 0.99 (where it reaches 2.5 nm -1 ), with a small shift back to 2. (Figure 8).…”

“…The total static structure factors, S(q), and pair radial distribution functions, g(r) were computed according to previously described methodologies. 36,58 …”

“…The COP has been identified in previous work as arising from characteristic distances within the polar network of the IL (see MD discussion below for details). 36,45 The low-q scattering for mixtures where x to the formation of small aggregates of the C12 chains from the [C 12mim] + ions within the polar network, which consists of the charged imidazolium groups and the [Tf 2N] -ions and is driven by hydrophobic effects. This low-q scattering has been fitted to the scattering models described above and derived parameters are shown in Table 2.…”

Local Structure in Terms of Nearest-Neighbor Approach in 1-Butyl-3-methylimidazolium-Based Ionic Liquids: MD Simulations

“…3,[27][28][29][30] Regarding the use of molecular simulations in explaining various spectroscopic observations one has to keep in mind that the vast majority of such experimental information reports the local molecular environment around specific sites of IL cations, e.g., 1 H NMR signals, CH vibrational bands, etc. [22][23][31][32][33][34] The importance of studying the influence of the anions on the microscopic structure around a reference cation is evident in this context.…”

Novel 2-alkyl-1-ethylpyridinium ionic liquids: synthesis, dissociation energies and volatility

“…7,15 Recently, a comprehensive molecular dynamics simulation study has been performed in order to complement and extend the structural analysis on the mesoscopic segregation observed in the ionic liquids of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C NÀ1 C 1 im][NTf 2 ]. 16 It was found that in the smaller members (C2-C4) of the ionic liquid series, the nonpolar aggregates form elongated clusters with an increasing number of tails per aggregate, which become more oblate around [C 5 16 The possibility of concisely tuning the physical-chemical properties by changing the cation-anion combination is one of the biggest advantages of these systems. For this purpose, the knowledge and understanding of structure-property relationships of ionic liquids is indispensable.…”