Efficient Preparation of Janus Particles with Controllable Morphology and Composition via Photopolymerization

Janus particles (JPs) with anisotropic shape and composition are of great significance in the fabrication of functional materials, but the efficient preparation of JPs and easy modulation of the JPs' lobe composition and morphology are still challenges. In this work, a method combining 'phase separation inside emulsion droplet' and photopolymerization was proposed for the one-pot preparation of JPs. In our strategy, two kinds of ultraviolet (UV)-curable prepolymers with different surface tensions were dissolved in a cosolvent and dispersed in an aqueous emulsifier solution. With the volatilization of the solvent, two prepolymers separated from each other, migrated to the two sides of the emulsion droplet, and converted to Janus particles via UV-initiated polymerization. The strategy possessed the advantages of convenience, high efficiency, mild conditions (room temperature), and high yield (>80%), which provided a reliable approach for the large-scale preparation of JPs. On the basis of the theory of spreading coefficient, we explored the effect of UV-curable prepolymers and emulsifiers on the morphologies of JPs (such as snowman and dumbbell), and the relationship between the morphologies and the interfacial tension between the prepolymers and the aqueous phase was systematically analyzed. In addition, the lobe ratio and the particle size of the JPs could be easily regulated by adjusting the feeding ratio and emulsification speed, which further broadened the regulation range of the JPs.