A rapidly switchable CO2-responsive Pickering emulsions based on supramolecular amphiphilic surfactants and nano-SiO2

A novel rapidly switchable CO 2 /N 2 -responsive Pickering emulsifier based on supramolecular amphiphilic surfactants (SDOA) and nano-SiO 2 has been fabricated. SDOA was constructed by mixing Jeffamine D-230 and oleic acid (HOA) at 1:1 stoichiometric ratio. Compared with conventional small-molecule emulsifiers, the novel rapidly switchable CO 2 /N 2 -responsive Pickering emulsifier was prepared with inexpensive raw materials by a simple method, and there was no contaminant generation during synthesis. A new CO 2 /N 2 -responsive Pickering emulsion was prepared on this basis, and its stable performance and responsiveness were investigated in depth. The results show that this emulsion can be stable for a long time (more than 30 days) at a low surfactant dosage (0.5 mmol/L) through in situ hydrophobization of SiO 2 nanoparticles by hydrogen bonding and electrostatic adsorption. In addition, the emulsion broke rapidly and completely after 10 s of CO 2 introduction into the stable emulsion, and the emulsion could be reconstructed in response to N 2 purging for 5 min at 60 ℃ followed by homogenization . The switching behavior of the emulsion is due to decomposition of the pseudo amphiphile by bubbling CO 2 into the system and both the protonated D-230 ions and the neutral HOA produced have no in situ hydrophobization to SiO 2 particles. At 60 ℃, the influx of N 2 will drive out CO 2 , making HOA re-transform into hydroxide ion, and after re-combining with D-230 ion, it can again perform in-situ hydrophobization on SiO 2 particles, thus forming a stable emulsion. Thanks to the ability of SiO 2 nanoparticles and D-230 ions to maintain electrostatic adsorption after the passage of CO 2 , compared with previous studies, the emulsion can be completely demulsified at a higher pH value (about 5.5), fewer bicarcarbonate roots are formed, less CO 2 needs to be introduced, and N 2 required to re-stabilize the emulsion is also reduced. This greatly increases the response efficiency of the emulsion and reduces the energy loss and the cost of putting the emulsion system into practical application. This research has important implications for fossil fuel generation, production and transportation of crude oil, and other areas.