Polymer reinforced silica aerogels: effects of dimethyldiethoxysilane and bis(trimethoxysilylpropyl)amine as silane precursors

This study evaluated the effectiveness of dimethyldiethoxysilane (DMDES) precursor in improving the elastic recovery behavior of silica aerogels reinforced with epoxy through amine sites on the silica surface. In the study, two aminosilanes - 3-aminopropyltriethoxysilane (APTES) and bis(trimethoxysilylpropyl)amine (BTMSPA) - were considered as reactive sites for cross-linking with epoxy. Because of the way the samples were formulated, BTMSPA offered half the number of amine sites compared to APTES at the same level of substitution. Replacing tetraethoxysilane (TEOS) with at least 15 mol% DMDES reduced the number of silicon-oxygen bonds in the aerogel networks and resulted in improved elastic recovery, but up to an order of magnitude lower compressive modulus. BTMSPA aerogels demonstrated strong elastic response without DMDES, with some samples showing near complete recovery. However, these aerogels offered lower modulus than APTES aerogels.