Nanoscale Tail Aggregation in Ionic Liquids: Roles of Electrostatic and van der Waals Interactions

Nanoscale spatial heterogeneity in ionic liquids is formed by the aggregation of cationic tail groups. The electrostatic interactions between polar groups and the collective van der Waals interactions between nonpolar tail groups both contribute to the formation of tail domains, but the degrees of their contributions were unknown. In this work, by applying a strong external electric field to effectively overpower the electrostatic interactions between polar groups, we have determined that the tail aggregation is majorly attributed to the electrostatic interactions and the van der Waals interactions only have minor influence on the spatial heterogeneity phenomenon of ionic liquids.