Distinctive Nanoscale Organization of Double- Cationic Versus Single-Cationic Ionic Liquids

Double-cationic ionic liquids are attracting the increasing research interests recently. In this work , the distinctive structural organization of double-cationic ionic liquids (DILs) with varying alkyl linkage chain lengths is systematically investigated using classical molecular dynamics (MD) simulations.  In comparison with their single-cationic ionic liquids (SILs) counterparts , DILs with varying length alkyl chains exhibit structural features that are different from SILs regardless of anion types. SILs are found to exhibit various structural heterogeneities that are more pronounced than DILs. Moreover , the predominant role of anion type in the structure of DILs was verified be analogous to that in MILs. In the end , the different nanoscale organizations of DILs and MILs are rationalized by straight- and folded-chain models proposed for the nanoaggregates in DILs and those in MILs.  This study provides molecular insights into the nature of structural heterogeneity in DILs as well as a theoretical model for the interpretation of experimental observations.