Regulating redox and pH- responsive behavior of emulsion by varying alkane carbon number of tertiary amine

Abstract

Tertiary amines (TA) are widely treated as the responsive additions of stimuli-responsive emulsion. The effect of alkane carbon number (ACN) of TA (N,N-Dimethyldecylamine (DMA), N,N-Dimethyldodecylamine (DMDA), N,N-Dimethyltetradecylamine (DMTA) and N,N-Dimethylhexadecylamine (DMHA)) on redox and pH- responsive behavior of emulsion was explored, obtaining a reference to regulate the redox and pH- responsiveness of emulsion precisely. Here, the emulsions are stabilized by the surfactant prepared simply with electrostatic interaction TA and ferrocenecarboxylic acid (FA). The stability of emulsion can be enhanced because of the enhanced surface activity of surfactant with increasing ACN of TA, which was demonstrated by the measurement of water separation ratio (WSR), micrographs and Zeta potential value of emulsion. In addition, by the analysis of micrographs, surfactant tension and interfacial tension, it is demonstrated that the more complete oil-water separation is regulated reversibly because of the larger change value of interfacial tension with increasing ACN upon the alternate addition of Na₂SO₃ and H₂O₂. Besides, the emulsions stabilized by surfactant prepared with TA containing ACN = 10 and 12 exhibit doubly pH-responsive behavior, which is ascribe to the inactivation of surface activity of surfactant at lower and higher pH. However, the emulsions stabilized by surfactant prepared with TA containing ACN = 14 and 16 exhibit single pH-responsive behavior because of the inactivatd surface activity of surfactant at higher pH and activatd surface activity of protonated DMTA and DMHA at lower pH.

Graphical Abstract

Keywords:

• Alkane carbon number
• tertiary amine
• redox and pH- responsive
• controllable surface activity

Additional information

Funding

The work was supported by the Open Fund of State Key Laboratory of Natural Gas Hydrates.