Self-Sensing shape memory boron Phenolic-Formaldehyde aerogels with tunable heat insulation for smart thermal protection systems

With the rapid development of new-generation aviation and space vehicles, the demand for deformable thermal protection systems and material technologies has emerged. Phenolic aerogels are appealing insulation materials for thermal protection. However, their inherent brittleness restricts their application. It is crucial to develop phenolic resins with high-temperature resistance and aerogels with excellent tunable thermal insulation properties to ensure a reliable smart thermal protection system. Herein, shape memory boron phenolic-formaldehyde resins with hyperbranched topologies were developed, which retained a 65 % residual mass under nitrogen at 1000 ℃ and a line ablation rate of 0.048 mm/s. The resins were endowed with excellent shape memory properties by the boron-oxygen bonds introduced into the cross-linking network. Shape memory boron phenolic-formaldehyde aerogels (SMBPFAs) with low density (0.18 g/cm³) and high porosity (89.3 %) were fabricated via template-in-situ polymerization. SMBPFAs exhibited outstanding thermal insulation performance and could withstand a 800 ℃ flame while maintaining a cold side temperature of only 162 ℃. Remarkably, SMBPFAs in temporary shapes can precisely regulate the thermal insulation performance on demand by altering the microstructure through shape recovery. As a proof-of-concept, we look forward to the application of SMBPFAs in smart thermal protection systems for future aircraft.