Tailorable Janus Silica Particles with Morphological and Functional Anisotropy for Enhanced Oil–Water Emulsion Stability

Particulate emulsifiers offer significant advantages in stabilizing oil-water emulsions with improved durability, uniformity, and compatibility for cosmetic and formulation applications. However, conventional particulate emulsifiers often suffer from unclear amphiphilic separation, indistinct functional anisotropy, and limited structural tunability, which severely restrict their emulsification efficiency and practical application in complex systems. To tackle these critical issues, a functionalization strategy to construct well-defined anisotropic Janus silica particles with distinct amphiphilic regions and controllable morphology was proposed in the current work. The particles were successfully modified using octyltriethoxysilane (OTES) and hexadecyltrimethoxysilane (HDTMOS), which clearly regulated the amphiphilic surface anisotropy. Particularly, the increase in the alkyl chain length of HDTMOS inhibited a part of tails overgrowth, while modification through OTES generated a highly stable hydrophobic interface with an emulsifying behavior. Compared with contemporary particulate emulsifiers, the optimized OTES-modified Janus particles exhibited very good emulsification performance in various oil phases, particularly showcasing significantly enhanced stability for the emulsion and prolonged emulsification time. The present work provides a reliable and scalable strategy for tailoring the performance of emulsifiers at the nanoscale for high-performance emulsions.