Self-Embedded PMMA Film Enabling High-Efficiency Radiative Cooling via Homogeneous Particle-Pore Architecture

Passive daytime radiative cooling (PDRC) technology has garnered significant attention as a sustainable cooling solution that enables subambient cooling without additional energy input. The current design strategy for PDRC films mainly relies on composite porous matrices containing inorganic nanoparticles, which have bottleneck problems, such as low material utilization, high process complexity, and high manufacturing costs. In contrast, herein we develop a self-embedded cooling film through nonsolvent-induced phase separation, where poly(methyl methacrylate) (PMMA) nanoparticles spontaneously embed within a PMMA porous matrix. Through the synergistic interaction between particles and pores, an efficient broadband solar light scattering network was constructed, yielding a high solar reflectance of up to 95%. Meanwhile, the integrated structural design enhances the vibrational modes of intrinsic chemical bonds in PMMA, thereby improving mid-infrared radiative performance and enabling a high infrared emissivity of 96%. In addition, the fabrication process is fully scalable, requiring no filler doping or post-treatment. The film delivers a temperature reduction of 15.8 °C under direct sunlight, underscoring its strong potential for practical deployment in passive radiative cooling applications.