Structural characterization of the [CnC1im][C4F9SO3] ionic liquid series: Alkyl versus perfluoroalkyl side chains

Abstract

This work represents an essential step towards the understanding at a molecular level of the bulk structure of ionic liquids (ILs) that exhibit both an hydrogenated and a perfluorinated alkyl side chain. Molecular Dynamics (MD) simulations were performed along the 1-alkyl-3-methylimidazolium perfluorobutylsulfonate homologous series, [CnC1im][C4F9SO3] (2≤n≤12) in order to study in a systematic way the effect on the bulk structure of the change of the ratios between polar and nonpolar moieties and between hydrogenated and fluorinated moieties. The MD trajectories were used to calculate global and partial structure factors, S(q), of each IL. The low-q peaks obtained from the deconvolution of the total S(q) functions were assigned to characteristic lengths of the polar network and non-polar domains, also computed via the appropriate pair radial distribution functions. Finally, several aggregation analyses were performed in order to emphasize the bicontinuous nature of the liquids and its systematic and complex evolution along the series.