Skeleton-interlocked HGM-hybridized PHP composite aerogels for fire safety, thermal insulation, and water-induced structural response

A skeleton-interlocked PHP composite aerogel was developed by incorporating HGM/g-C 3 N 4 /MoS 2 hierarchical fillers into a poly(vinyl alcohol)/hydroxypropyl methylcellulose/polyvinylpyrrolidone matrix, forming an interlocked filler-skeleton framework. The optimized PHP/MH-gC 3 N 4 -2 retained a highly porous skeleton with a porosity of 89.86%, while showing a 197.57% increase in compressive strength, reductions of 58.12% and 89.66% in peak heat release rate and total smoke production, respectively, and a V-0 rating without flaming drips. It also exhibited a thermal conductivity of 0.197 W/(m·K) and a thermal diffusivity of 0.19 mm 2 /s, maintaining temperature differences of 82.7 °C and 38.7 °C in the 120 °C hot-plate and −30 °C cold-plate tests, respectively. After 10 absorption-squeezing cycles, PHP/MH-gC 3 N 4 -2 retained a water uptake capacity of 11.31 g/g and exhibited wet-state shape recovery. These results demonstrate a filler-skeleton interlocking strategy for constructing fire-safe, thermally protective, mechanically robust, and water-responsive polymer aerogels.