Architected Spatially Deterministic Multiscale Phase Segregation in Block Copolymer Composites for Augmented Radiative Cooling.

Passive radiative cooling, which reflects solar irradiation while emitting heat through the atmospheric window, provides a sustainable solution for zero-energy thermal management. Simultaneously achieving high solar reflectivity and infrared emissivity remains challenging since the structural parameters governing light scattering and thermal radiation are intrinsically coupled. A block copolymer composite (denoted SEDO) of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was judiciously designed and architected through multiscale phase segregation to enable decoupled structure-determined spectral regulation. Macroscopic phase segregation in SEDO endows three-dimensionally interconnected porous skeleton that enhances broadband Mie scattering, resulting in a high solar reflectivity of 97.2%. Meanwhile, DOPO fillers that selectively located in the polystyrene domains introduce strong molecular vibrational absorption within the atmospheric window. The cylindrical microphase separation morphology enables an emissivity of 95.5% with only 5 vol% additive. Benefiting from this decoupled optical regulation, the composite achieves sub-ambient cooling of ∼8.1°C under clear-sky conditions and ∼6.3°C under cloudy conditions, while maintaining efficient heat dissipation under high heat flux. Combined with excellent mechanical flexibility, flame retardancy, and environmental stability, this multiscale phase segregation strategy provides a versatile platform for augmented radiative cooling in practical thermal-management applications via crafting spatially deterministic block copolymer composites.