Bioinspired Homologous Gradient Interphase Sustains Phase‐Change Buffering and Radiative Cooling Under Thermal Shocks

ABSTRACT Coupling phase‐change buffering with passive radiative cooling offers complementary continuous and transient regulation for personal thermal management (PTM). In fibrous systems, however, repeated phase transitions drive molecular rearrangement and thermomechanical stress accumulation, causing fiber deformation, pore collapse, and irreversible deterioration of radiative cooling performance. Herein, inspired by graded stress transfer in mussel byssus, we develop a homologous gradient interphase strategy to construct a core–gradient interphase–shell fibrous membrane (Ho‐GIFM) for durable PTM. During coaxial electrospinning, homologous polyethylene glycol‐based polyurethanes interdiffuse and entangle across the interface, while in situ UV crosslinking stabilizes the interphase. This structure redistributes phase‐change‐induced strain and constrains long‐range chain rearrangement, preserving phase‐change functionality and porous fiber networks. Ho‐GIFM exhibits a broad solid‐solid phase‐transition window (30.2–51.5°C) with a competitive melting enthalpy (60.2 J g −1 ). Notably, after 100 alternating thermal shocks between −40 and 80°C, Ho‐GIFM retains 99.0% of its initial solar reflectance versus only 74.5% for the heterogeneous counterpart, together with 99.9% mid‐infrared emissivity retention. Furthermore, it delivers a calculated daytime net radiative cooling power of 101.9 W m −2 and achieves an average synthetic‐skin temperature reduction of 14.9°C. This work provides an interfacial design strategy for durable PTM and multicomponent functional fibers.