Ultralow-loading carbon nanotube-induced framework regulation in polymethylsilsesquioxane aerogels for reduced thermo-oxidative hazard

Polymethylsilsesquioxane (PMSQ) aerogels are promising lightweight thermal insulators owing to their low density, low thermal conductivity, and hydrophobic organosiloxane frameworks. However, their methyl-containing skeleton remains susceptible to thermo-oxidative degradation at elevated temperatures. In this work, ultralow-loading carbon nanotubes (CNT) were incorporated into ambient-pressure-dried PMSQ aerogels to clarify whether CNTs can serve as structure-regulating nanoelements rather than conventional high-loading thermal fillers. The microstructures and skeleton statistics reveal that CNT incorporation progressively refines the PMSQ aerogels’ frameworks, decreasing the mean skeleton diameter from 2.79 ± 1.38 μm to 1.37 ± 0.92 μm and markedly suppressing the large-diameter skeletal tail. The accessible pore network shifts toward smaller and more confined characteristic dimensions, while the thermal conductivity remains nearly unchanged at approximately 29–30 mW/m/K. 29 Si ssNMR and FTIR results confirm that the dominant PMSQ network chemistry is preserved, indicating that the performance evolution arises mainly from network structural reorganization rather than a fundamental compositional change. Thermal analysis and kinetics demonstrate monotonic increases in the onset temperature and peak temperature of thermal decomposition across all the CNT/PMSQ aerogels, together with a reduced contribution from the dominant mass-loss process, decreased exothermic enthalpy and gross calorific value, and increased apparent activation energy. These findings establish a structure-stability-safety relationship in CNT/PMSQ aerogels and provide a low-loading strategy for improving the thermo-oxidative robustness of PMSQ aerogel thermal insulators.