Self-assembly in surfactant-based liquid mixtures: Bis(2-ethylhexyl)phosphoric acid/bis(2-ethylhexyl)amine systems

Surfactant-based liquid mixtures constitute an interesting class of nanostructured materials with promising potential in specialized applications. Here, structural and conductometric properties of liquid mixtures composed of bis(2-ethylhexyl)amine (BEEA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) have been thoroughly investigated with the aim to correlate structural features with system charge transport capability. The evolution of self-assembled local nanostructures with system composition has been investigated by FT-IR and XRD while the conductometric properties were probed by conventional AC complex impedance. Both pure components exhibit nano-segregation due to their amphiphilic nature but with only very low proton conductivities. However their mixtures, characterized by local organization of polar and apolar domains driven by acid–base interactions between HDEHP PO4H and BEEA NH groups, show enhanced structural order and proton conductivity.

Graphical abstractSchematic representation of the possible local hydrogen-bonded structure of HDEHP/BEEA mixtures leading to the formation of local networks where protons and proton holes can travel by a jumping mechanism.Figure optionsDownload full-size imageDownload high-quality image (99 K)Download as PowerPoint slide