Eco-Friendly Flame-Retardant Phase-Change Composite Films Based on Polyphosphazene/Phosphorene Hybrid Foam and Paraffin Wax for Light/Heat-Dual-Actuated Shape Memory

Multiactuated shape memory materials are a class of promising intelligent materials that have received great interest in the fields of self-healing, anticounterfeiting, biomedical, soft robotic, and smart thermal management applications. To obtain a light/heat-dual-actuated shape memory material for thermal management applications in fire safety, we have designed a type of halogen-free flame-retardant phase-change composite film based on polyaryloxyphosphazene (PDAP)/phosphorene (PR) hybrid foam as a support material and paraffin wax (PW) as a phase-change material (PCM). PDAP was synthesized as a flexible foam matrix through the ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a substitution reaction of aryloxy groups. The porosity of the PDAP foam is improved by introducing PR nanosheets, facilitating a high latent heat capacity of the PDAP-PR/PW composite films for thermal management applications. The PDAP-PR/PW composite films can implement rapid shape recovery within 65 s in the heating process, which is much shorter than that of the corresponding film without PR nanosheets (185 s). Furthermore, the PDAP-PR/PW composite films also exhibit light-actuated shape memory behavior thanks to their good solar-to-thermal energy absorption and conversion contributed by PR nanosheets as a highly effective photothermal material. More importantly, the presence of PR nanosheets imparts an excellent flame-retardant property to the PDAP-PR/PW composite films. The PDAP-PR/PW composite film can be self-extinguished within 2 s after the flame. Through an innovative integration of flexible polyphosphazene foam, PR nanosheets, and solid-liquid PCM to obtain a sensitive actuating response to light and heat, this study offers a new approach for developing multiactuated and eco-friendly flame-retardant shape memory materials to meet the requirement of applications with a requirement of fire safety in soft actuators, thermal therapy, control devices, and so on.