Beyond Surfactants: Janus Particles for Functional Interfaces and Coatings.

Janus particles (JPs), initially introduced as soft matter, have evolved into a distinctive class of materials that set them apart from traditional surfactants, dispersants, and block copolymers. This mini-review examines the similarities and differences between JPs and their molecular counterparts to elucidate the unique properties of JPs. Key studies on the assembly behavior of JPs in bulk phases and at interfaces are reviewed, highlighting their unique ability to form diverse, complex structures. The superior interfacial stability and tunable amphiphilicity of JPs make them highly effective emulsifiers and dispersants, particularly in emulsion polymerization systems. Beyond these applications, JPs demonstrate immense potential as coating materials, facilitating the development of eco-friendly, anti-icing, and antifouling coatings. A comparative discussion with zwitterionic polymers also highlights the distinctive advantages of each system. This review emphasizes that while JPs mimic some of the behaviors of small molecular surfactants, they also open doors to entirely new applications, making them indispensable as next-generation functional materials.