One-Component Stereoscopic Oligosiloxane-Based Polyurea Radiative Cooling Coatings

Passive daytime radiative cooling (PDRC) technology is an emerging and promising zero-carbon solution. However, existing PDRC materials usually exhibit poor mechanical properties and lack self-cleaning ability, which can reduce the lifespan of the coating and affect its cooling effect. To address these challenges, a one-component stereoscopic oligosiloxane-based polyurea radiative cooling coating is developed. The coating is fabricated by integrating blocked amine-oligosiloxane nanoclusters, isocyanate-terminated curing agents, and inorganic aluminum oxide (Al₂O₃) particles. The unique stereoscopic oligosiloxane structure, characterized by high functionality and self-reinforcing effect, endows the polyurea with a highly cross-linked organic-inorganic hybrid network structure. This structure provides exceptional hardness and modulus for the coating, with a surface hardness of ≈227 Mpa and a modulus of ≈9.7 Gpa. In addition, the high infrared emissivity of Si─O─Si bonds and the high reflectivity of Al₂O₃ enable the coating to have an excellent cooling effect of ≈9 °C below ambient temperature during the daytime. The coating also exhibits excellent versatility. The introduction of polydimethylsiloxane (PDMS) endows the coating with excellent self-cleaning and antifouling properties. Furthermore, spraying fluorinated nanosilica (F─SiO₂) on the surface enables superhydrophobicity and water droplet power generation. The novel PDRC coating provides a sustainable solution for cooling buildings.