Redox and pH Dual-Responsive Emulsion Using Ferrocenecarboxylic Acid and N,N-Dimethyldodecylamine.

The derivatives of ferrocene with redox properties are widely used. Some studies have used complex synthesis processes to obtain surfactants with redox properties. In order to simplify the synthesis process, FA-DMDA-Ox, a surfactant with redox and pH dual responses, was prepared by simple electrostatic interaction between ferrocenecarboxylic acid (FA) and N,N-dimethyldodecylamine (DMDA). A stable oil-in-water emulsion was prepared by using FA-DMDA-Ox at 25 °C. When sodium sulfite was added to the emulsion, the emulsion was demulsified. This was due to the oxidized ferrocene group that was reduced from the charged hydrophilic state to the uncharged hydrophobic state, which destroyed the original surface activity. In addition, when added HCl or NaOH to the emulsion changed pH, demulsification was caused by the dissociation of FA-DMDA-Ox.