CO₂-triggered switchable Pickering emulsion stabilized by guanidine-functionalized silica particles

ABSTRACT

The guanidine group-modified silica particles were used as emulsifier to obtain a CO₂-responsive Pickering emulsion. To compare the wettability effect of the particles on the stability of the emulsion, both guanidine and alkyl chain were attached on the surface of silica particles. The influences of tension, particles concentration, oil-water fraction, NaCl concentration, and CO₂ on Pickering emulsion properties were investigated. Although the particles did not decrease the surface and interfacial tensions of the air/oil-water interfaces, they attached on the oil–water interfaces and stabilized the emulsions at room temperature for at least 4 weeks. Addition of salt increased the emulsion stability and induced phase inversion at high salt concentration. The stabilization–destabilization cycles of the emulsion could be successively controlled by alternative CO₂/heating triggers due to the protonation-deprotonation of guanidine groups on the particle surfaces.

GRAPHICAL ABSTRACT

KEYWORDS:

• CO₂-responsive nanoparticle
• emulsion stability
• Pickering emulsion

Additional information

Funding

The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (No. 91534103), the 111 Project of the Ministry of Education of China (No. B08021), and the Fundamental Research Funds for the Central Universities of China (No. 222201717003).