Highly flexible phase change composite materials with photothermal response enable day-and-night thermal energy management for pipelines

Solid-solid phase change materials (SSPCMs) are widely recognized as highly promising candidates for applications in the field of thermal energy storage and management. However, due to their limited functionality and weak mechanical strength, progress in exploring the practical applications of SSPCMs has been limited to date. Here, we propose a green and environmentally friendly strategy for manufacturing photothermal composite SSPCM with high latent heat and mechanical strength. A triethanolamine-containing polymer promotes cross-linking and the formation of hydrogen bonds between molecules. Additionally, SSPCM is doped with carboxylated carbon nanotubes (CNTs-COOH) to synthesise composite phase change materials. This method enables the composite phase change material to exhibit high phase change enthalpy (101.2 J/g), excellent flexibility, outstanding tensile strength (~43.0 MPa), and significant tensile strain (1160.0 %). Furthermore, owing to intermolecular cross-linking and the presence of CNTs-COOH, these composites also exhibit excellent shape stability, shape memory functionality, self-healing capability, and high thermal conductivity. Finally, photothermal characterization demonstrated that incorporating 5 % CNTs-COOH into the phase change material yielded a photothermal conversion efficiency of 83.04 %. Based on this result, a sustainable heating strategy was developed, enabling cyclic daytime heat storage and nighttime heat release.