Fabrication of thermo-responsive Janus silica nanoparticles and the structure–performance relationship in Pickering emulsions

The application of thermal-responsive Janus particles as emulsion stabilizers in oil–water systems has attracted increasing attention in recent years. This work reported a novel Janus silica nanoparticle with one silanol side and one poly(N-isopropylacrylamide) (PNIPAM) side, which was fabricated via combining interfacial synthesis method and single-electron transfer living radical polymerization (SET-LRP) process. Their structure and surface properties were identified by SEM, TEM, 1H NMR, FTIR, and TGA. The thermo-responsive performance of Janus nanoparticles in oil–water Pickering emulsion systems was also investigated as well as their emulsification properties in both the tetradecane–water and crude oil–water systems. The solubility of both Janus and symmetric PNIPAM-modified silica nanoparticles in water presents reversible thermal-responsive properties. Notably, the Janus nanoparticles show a higher phase transition temperature than the symmetric nanoparticles because the presence of silanol on one side of the Janus nanoparticles enhances its hydrophilicity due to the stronger hydrogen bond at high temperature. In comparison with symmetric nanoparticles, Janus nanoparticles exhibit superior emulsification performance in the tetradecane–water system as a result of their lower surface tension. Janus nanoparticles also present excellent thermal-responsive emulsification performance in the crude oil–water system, showing a prospective future in industrial application as a surfactant.