Recyclable Solid-Solid Phase Change Materials with Superior Latent Heat via Reversible Anhydride-Alcohol Crosslinking for Efficient Thermal Storage.

Solid-solid phase change materials (SSPCMs) with crosslinked polymer structures have received sustained interest due to their remarkable shape stability, enabling their application independently without the need for encapsulation or supporting materials. However, the crosslinking structure also compromises their latent heat and poses challenges to their recyclability. Herein, a novel strategy harnessing the internal-catalyzed reversible anhydride-alcohol crosslinking reaction to fabricate SSPCMs with superior latent heat and exceptional dual recyclability is presented. Easily accessible anhydride copolymers (e.g., propylene-maleic anhydride alternating copolymers), provide abundant reactive anhydride sites within the polymer matrix; polyethylene glycol serves as both the grafted phase change component and the crosslinker. The resulting SSPCMs attain a peak latent heat value of 156.8 J g which surpasses all other reported recyclable crosslinked SSPCMs. The materials also exhibit certain flexibility and a tunable tensile strength ranging from 6.6 to 11.0 MPa. Beyond that, leveraging the reversible anhydride-alcohol crosslinks, the SSPCMs demonstrate dual recyclability through bond-exchange remolding and reversible-dissociation-enabled dissolving-recrosslinking without any reactive chemicals. Furthermore, by integrating solar-thermal conversion fillers like polydopamine nanoparticles, the potential of the system in efficient conversion, storage, and release of solar energy is highlighted.