Preparation of Multifunctional Polyacrylate-Based Hollow Microspheres and Its Applications in Radiative Cooling

Polymer-based direct radiative cooling (PDRC) materials have attracted increasing attention due to their diverse functional groups and high emissivity within the atmospheric window (8–13 µm). This study introduces a new class of hollow microspheres featuring a multifunctional poly-trimethylolpropane triacrylate (PTMPTA) shell for enhanced radiative cooling. These microspheres are synthesized via radical-initiated interfacial polymerization using heptane as the core and PTMPTA as the shell precursor, followed by thermal evaporation of the n-heptane core. The resulting hollow structures exhibit uniform morphology with ~2 μm diameter and ~50 nm shell thickness. The inner cavities facilitate strong light scattering and efficient thermal emission. The microspheres are integrated onto fabric substrates through a scalable coating process, forming composite fabrics with superior spectral selectivity. The coatings achieve solar reflectance exceeding 80% (0.3–2.5 μm) and infrared emissivity above 90% (8–13 μm), effectively reducing solar heat gain while enhancing radiative heat loss. Outdoor comparative measurements against uncoated fabric substrates further demonstrate the cooling advantage of the composite coating: Under typical outdoor conditions (solar irradiance >1 kW/m2), the surface temperature of the coated fabric was consistently lower than that of the pristine fabric, with a maximum temperature difference of 6.9°C. Skin surface tests demonstrated a temperature reduction of approximately 2–3°C when covered by the coated fabric. These results underscore the material’s potential for practical passive cooling applications in outdoor equipment, wearable textiles, and architectural coatings.