Cellulose nanocrystals-regulated core-shell fibrous films for synergistic radiative cooling and phase change thermal management

Thermal comfort is increasingly challenged by heat waves and abrupt temperature fluctuations, requiring materials that dissipate heat while buffering thermal shocks. Existing combinations of radiative cooling and phase change systems are often achieved by stacking or mixing components, leaving structural design and performance regulation largely independent, which limits the mutual reinforcement of steady cooling and transient thermal regulation. Herein, we employ coaxial electrospinning to construct a core-shell fibrous film composed of polyethylene glycol@poly (vinylidene fluoride-co-hexafluoropropylene)/cellulose nanocrystals (PEG@PVDF-HFP/CNCs) for the synergistic regulation of radiative cooling and phase change performance. The shell achieves 94.91% solar reflectivity (0.3-2.5 μm) and 97.56% infrared emissivity (8-13 μm), while the core provides high thermal shock resistance with a phase change enthalpy of 47.3 J g⁻¹. Crucially, CNCs enhance radiative cooling by optimizing structural scale and optical parameters, while simultaneously improving phase change thermal regulation by inducing PEG crystallization to enhance latent heat storage, achieving synergistic enhancement of both functions within the same material system. Outdoor measurements demonstrate a steady-state temperature reduction of 10.5°C together with effective buffering against abrupt ambient temperature fluctuations. This work achieves synergistic optimization of radiative cooling and phase change performance within one system, providing a novel pathway for thermal comfort regulation under dynamic environments.