Tailoring Interconnected Microporous Networks in Wet-Spun Cellulose Acetate Composite Fibers for Synergistic Thermal Management and Radiative Cooling

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Fibrous radiative cooling materials typically rely on high porosity to enhance solar reflectance, yet excessive porosity significantly impedes thermal conduction, creating a barrier to metabolic heat dissipation. Here, we propose a cellulose acetate/poly(vinylidene fluoride) (CA/PVDF) porous fiber with a bicontinuous sponge-like structure prepared via nonsolvent-induced phase-separation (NIPS) wet spinning. A highly interconnected microporous network is formed due to the suppression of macrovoids during thermodynamically stable solvent exchange. With the dense micropores maximizing solar scattering to block external heat and the continuous solid skeleton preserving conductive pathways for body heat transport, the obtained fiber achieves a critical balance between optical shielding and thermal transmission. Consequently, the fiber exhibits a high solar reflectance of 96.27%, an infrared emissivity of 90.15%, and a moderate thermal conductivity of 0.051 W/(m·°C). This yields a theoretical cooling power of 95.78 W/m2 and a subambient temperature reduction of 8 °C. Notably, the fibers demonstrate robust environmental stability, retaining >95% reflectance after 100 h of UV aging. This work offers a scalable route for flexible radiative cooling textiles and advances their deployment in personal thermal management.