Hydrophilic–Lipophilic Regulation by Amphiphilic Silicon-Based Janus Nanoparticles

Amphiphilic Janus nanomaterials have shown great potential for applications in oilfield extraction. However, the complex oil–water environment poses higher requirements for the regulation of the amphiphilic properties of Janus nanomaterials. In this paper, different silane couplers were used to graft different hydrophobic carbon chains on one side of the hydrophilic nano-SiO2 by interfacial protection. Amphiphilic Janus nano-SiO2 particles (AJNSPs) with varied interfacial properties were synthesized. Tests on the interfacial behavior of AJNSPs indicated that grafting varying hydrophilic and hydrophobic groups could effectively enhance the interfacial activity, wettability, and emulsification properties. AJNSPs-6, modified on both sides, significantly reduced interfacial tension from 31.3 to 10.17 mN/m. AJNSPs-6 with superior interfacial activity also demonstrated a stronger capability to alter the core wettability and had better emulsion stability. In enhanced oil recovery (EOR) experiments, the EOR performance was enhanced with an increase of the length of the carbon chain on the surface of the particle. The EOR effect of AJNSPs-6 reached 26.13%. In addition, by adjusting the embedding depth of SiO2 nanoparticles on the surface of Pickering emulsion, the amphiphilic characteristic of AJNSPs was altered without changing the species of hydrophilic–lipophilic groups on the surface, thus obtaining different emulsifying properties and interfacial activity. This method can design nanoparticles with different interfacial properties and significantly increase the adaptability of amphiphilic nanomaterials to different oil–water systems.