VTMS-based aerogel structure preservation: the influence of the sol–gel synthesis composition, aging process, and double-crosslinking

Abstract

Aerogels are highly porous materials that have a wide range of potential applications due to their exceptional properties – such as ultra-low density, high specific surface area, and low thermal and acoustic conductivity. One of the precursors gaining popularity in the aerogel synthesis is vinyltrimethoxysilane (VTMS) – due to the presence of the vinyl group which enables the modification of the aforementioned materials. However, VTMS still remains underexplored due to its synthesis challenges – such as frequent need for surfactants and difficulties in structure preservation during the ageing and drying processes. This study proposes a methodology for fabricating mesoporous VTMS-based aerogels via surfactant-free synthesis. The paper also identifies two primary mechanisms of structural degradation: dissolution during solvent exchange and shrinkage during aging and drying. The results indicate that the most effective way to prevent dissolution is the use of methanol in the solvent exchange process, which also eliminates cracks in the final aerogel structure. Shrinkage was found to be most effectively reduced by maintaining the sample in the mother liquor at an elevated temperature, while vulcanization proved to be an even more efficient method. Additionally, the study determines the synthesis compositions that enable the fabrication of the lowest-density aerogels.