A Surface-Micellar-Assembled Aerogel for Efficient Building Cooling

Passive daytime radiative cooling (PDRC) is a green and sustainable approach to building temperature regulation, contributing to global carbon neutrality. Although notable advances have been made in improving the cooling performance of PDRC materials, the use of reflective particles in polymer matrices often suffers from poor dispersion stability, limiting practical applications. Herein, we propose a strategy for constructing a composite material with an enhanced PDRC performance. The material was synthesized via thermally initiated polymerization of acrylamide, with calcium ions cross-linking sodium alginate to form a stable cross-linked network. To further boost solar reflectance, sodium dodecyl sulfate, which can be evenly dissolved and dispersed, was added to induce self-assembly and phase separation, facilitating critical micelle formation. This led to a three-dimensional skeletal semi-interpenetrating structure. After freeze-drying, the resulting acrylamide-sodium alginate (SAM) aerogel featured micellar-assembled and spectral properties, achieving an average solar reflectance of 0.8934 and an infrared emissivity of 0.9822 within the atmospheric window. In outdoor experiments, simulated houses covered with SAM/SDS-M(Top)-T3 mm showed an average indoor temperature difference of up to 4.04 °C compared to that of uncovered samples. Under a solar irradiance of 1040 W/m², the daytime cooling temperature dropped by 8.54 °C. Additionally, the material exhibited mechanical strength and thermal insulation. This work offers a design strategy for advancing practical PDRC technologies.