Recyclable and self-healing polyurethane composites based on Diels-Alder reaction for efficient solar-to-thermal energy storage

Development of recyclable and self-repairing phase-change materials, which enable renewable energy storage and sustainable development, is critical for the efficient utilisation of solar energy. Hence, we herein fabricated form-stable, reversible cross-linked polyurethane phase-change materials composites (DPCM-x) with excellent recyclability, outstanding self-healing ability (93.1%) and superior photo-thermal conversion efficiency (87.9%). Furan-modified polydopamine particles (f-PDAPs), which serve as cross-linkers and photo-thermal fillers, were incorporated into maleimide-terminated polyurethane phase-change materials via a Diels–Alder (DA) reaction. Sunlight irradiation experiments revealed that f-PDAPs addition significantly improved the storage efficiency and photo-thermal conversion of DPCM-x thanks to the superior solar-to-thermal energy conversion performance of the f-PDAPs. Additionally, the existence of both reversible DA networks and f-PDAPs ensured that DPCM-x composites had excellent near-infrared- (NIR-) induced self-healing abilities, thermal-induced recyclable properties and solid-state plasticity. Meanwhile, the recovered DPCM-x composites could largely maintain their original mechanical properties (90.1%) and thermal energy storage capacity. Such cross-linked polyurethane PCM composites exhibited excellent self-healing properties under NIR irradiation. Due to their outstanding recyclability, interesting energy storage ability and form stability, they have enormous potential for applications in the fields of solar-to-thermal energy conversion and storage.