Facile synthesis of macroporous foams with unique bone-like structure for the encapsulation of polyethylene glycol by sodium alginate for thermal energy storage

The encapsulation of solid-liquid phase change materials (PCMs) provides good shape stability and mechanical strength for further applications in thermal management, which is an attractive topic in the development of materials for thermal energy storage. In this work, a novel and facile strategy was developed for the encapsulation of polyethylene glycol (PEG). Hydrogels containing sodium alginate (SA) and PEG were first prepared through the formation of hydrogen bonds or chelation with metal ions including Ca 2+ , Ce 3+ and La 3+ . Then, macroporous foams with a unique “bone-like” structure were synthesized via freeze-drying while PEG was encapsulated as “bone marrow” by SA. The foams exhibited varied microstructures with different preparation strategies. After mold pressing, the PCMs maintained excellent shape stability at temperatures much higher than the melting point of PEG. They provided high latent heat, reaching 167.26 J/g, and high relative latent heat efficiency. After 200 thermal cycles, the latent heat retention rate remained as high as 97.06 %. This study establishes a promising approach for the encapsulation of PEG as a shape-stable PCM. Furthermore, the heterogeneous structure of the foams synthesized in this work shows great potential for the development of novel functional materials.