Emulsion‐based monoliths with a solid‐gel phase‐transition and a solid–solid phase‐transition for latent heat storage

Emulsion‐based, phase change material‐encapsulated monoliths are promising for latent heat storage. However, such monoliths usually exhibit a solid–liquid phase‐transition and the one‐only phase‐transition might hinder the monoliths for more potential applications. Herein, we report the synthesis of emulsion‐based monoliths with a solid‐gel phase‐transition and a solid–solid phase‐transition for latent heat storage. The solid‐gel phase‐transition was from melting and crystallization of octadecane‐in‐crosslinked poly(octadecyl acrylate) that was formed via radical polymerization of the dispersed phase within oil‐in‐water emulsions, and the solid–solid phase‐transition was from melting and crystallization of the crosslinked polyethylene oxide blocks that were synthesized via the interface‐initiated radical polymerization of the continuous phase. The resulting emulsion‐based monoliths showed negligible mass loss during the heating at 60 °C for 8 h, and exhibited two different crystallization (heat release) temperatures and melting (heat storage) temperatures, corresponding to the solid‐gel transition and the solid–solid transition. Moreover, the monoliths possessed quite high heat density (up to 136.4 J/g), and the heat density did not deteriorate over 20 heating–cooling cycles, showing high reusability. The extremely low leakage, double phase‐transitions and the high reusability make the monoliths to be a good candidate for latent heat storage.