Self-Stratifying Coating with Robust and Durable Superhydrophobic Underlayer Constructed by Amphiphilic Janus Nanoparticles

The multifunctional gradient self-stratifying coating (SSC) is attractive in many applications, but the robustness and durability of the functionalities still remains challenging. Here, a water-based SSC composed of amphiphilic Janus nanoparticles (JNPs) and binder latex is constructed by an extremely simple one-step drying method. The surface-partitioned “soft–hard” JNPs are specially designed and synthesized, in which the hard side of the JNPs (fluorosilane modified silica) imparts hydrophobicity and mechanical strength to the SSC, and the soft side contributes to the uniform dispersion of the hydrophobic JNPs in a water-based mixture and strong adhesion of JNPs to binder. Coatings with various microstructures and properties could be obtained simply by adjusting the binder solid content. Among them, the desirable SSC with a binder-rich upper layer and a JNPs-rich lower layer possesses a smooth surface and a superhydrophobic underlayer. The superhydrophobic underlayer of this SSC exhibits durable superhydrophobicity after 300 abrasion cycles and remarkable water repellency after heavy pull-off as well as good flexibility (film-forming). Our designs could provide new strategies for the development of low-cost and high-performance water-based SSC.