Tuning macroporous structure and thermal properties of polymethylsilsesquioxane aerogels via tailored heat treatment

Abstract

The rapid preparation of polymethylsilsesquioxane (PMSQ) aerogels via ambient pressure drying resolves the issues of organic solvent overconsumption and lengthy processing commonly encountered in the production of hydrophobic SiO₂ aerogels. However, macropore structures in MSQ aerogels diminish thermal insulation properties, limiting their broader application. This study employed a simple, clean, and controllable heat treatment technique to tailor the microstructure and surface chemical of MSQ aerogels, yielding SiO₂ aerogels with superior hydrophobicity, outstanding thermal insulation performance, and enhanced thermal stability. Specifically, through heat treatment at 600 °C in an argon atmosphere, MSQ aerogels demonstrate minimal morphological changes (2.5 % volume shrinkage), maintaining low density (0.066 g/cm³), high porosity, and excellent hydrophobicity. Notably, Reduced macropores optimize thermal conductivity (27.3 mW/m/K), while the partial decomposition of organic groups enhances thermal stability and lowers gross calorific value. This study offers a promising strategy for improving the thermal properties of MSQ aerogels and broadening their applications.