Unstable Supramolecular Structure of [Bmim][BF4] in Aqueous Solution

To unravel the exact composition and structure of aggregates in an aqueous solution of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]), we performed static and dynamic light-scattering measurements, as well as transmission electron microscopy (TEM). Results from this work show that the aggregates are vesicles and unstable; herein, we discuss the driving force behind the self-assembly. Apart from the van der Waals forces and repulsive electrostatic interactions between adjacent cation clusters, the hydrogen-bonding forces as well as counterion effects might also contribute to this driving force. The information obtained here is useful for a better understanding of the vital role that aggregation behavior plays in the field of ionic liquid recovery, and its potential use in controlled release, drug delivery, and petroleum recovery.