Thermotropic flexible composite phase change materials with high photothermal conversion for wearable thermotherapy

Phase change materials (PCMs) have shown broad prospects in wearable thermotherapy. High-performance thermotropic flexible PCMs are crucial for the practical requirements of persistent and wearable thermotherapy. Especially, the microstructures of carriers play an important role in their performance. In this study, the centrosymmetric, thermally responsive, flexible composite PCMs are tailored for wearable thermotherapy applications. By taking polyvinyl alcohol and hydroxyethyl cellulose as carriers, together with graphene oxide as a filler, the aerogel was constructed by radial freeze-casting technology. The structural growth mechanism under temperature gradient regulation was analyzed. Following the vacuum impregnation with polyethylene glycol, the composite PCMs exhibited anisotropic thermal conductivity, which was verified by experiments and simulations, and measured values of 0.775 W m −1 K −1 and 0.846 W m −1 K −1 in the axial and radial directions, respectively. This structure enhanced photothermal conversion efficiency and promoted rapid and uniform heat distribution. The composite PCMs showed thermally triggered flexibility and superior thermal stability during phase transition and maintained at 40-42 °C for 18.5 min under illumination. These integrated properties make the biomass-based composite PCMs with oriented structure a promising candidate for thermotherapy applications.