Aggregation behavior of dodecyltriphenylphosphonium bromide in aqueous solution: Effect of aromatic ionic liquids

• A kind of room-temperature ILs with aromatic anions was successfully synthesized.
• The aromatic ILs affect the micellization of a surfactant with aromatic headgroups.
• The enhanced π–π stacking interaction and hydrophobic interaction play a key role.

The effects of ionic liquids (ILs), 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) and 1-butyl-3-methylimidazolium benzoate ([Bmim][PhCOO]) on the aggregation behavior of dodecyltriphenylphosphonium bromide (C12TPB) in aqueous solution were investigated by surface tension measurements, dynamic light scattering (DLS) measurements and 1H NMR spectroscopy. The introduction of benzene rings in the anions of [Bmim][PhCOO] can promote the micellization of C12TPB more efficiently with a smaller CMC value and a bigger micellar size. The 1H NMR spectra revealed that [Bmim][PhCOO] can participate in the micelle formation. The combined effect of intermolecular interactions, such as electrostatic attraction, hydrophobic effect and π–π stacking interaction is proposed to be responsible for the enhancement in the micellization of C12TPB.

Surface tension curves of C12TPB/[Bmim][PhCOO] system and the proposed mechanism.Figure optionsDownload as PowerPoint slide