Flexible APD silica aerogels derived from Methyltriethoxysilane and Dimethyldiethoxysilane via surfactant-free sol-gel process

In this work, flexible silica (SiO2) aerogels were prepared, using Methyltriethoxysilane (MTES) and Dimethyldiethoxysilane (DMDES) as co-precursor, via two-step acid/base catalyzed sol-gel process and the following ambient pressure drying (APD) process, without using any surfactant. The molar ratio of MTES/DMDES and the concentration of the central silicon, influenced not only on the morphology and physical performance of the final samples, but also on the specific mechanism of the sol-gel chemistry. The results of FTIR, XPS, SEM images, stress-strain curves, etc for the final samples would illustrated these influence. And moreover, based on the similarity between the sol-gel process of siloxanes precursors and the network step polymerization of organic monomers, some basic concepts and theories in organic polymerization, such as the average functionality and Carothers equation, were adopted to discuss the reactive mode of MTES/DMDES co-precursor. Therefore, this work might be helpful for future research into functionally diverse, robust silica aerogels.Graphical AbstractThe MTES/DMDES hybrid silica aerogels were prepared via two-step acid/base catalyzed sol-gel process and the following ambient pressure drying (APD) process, without using any surfactant. The abundant of methyl moieties, introduced by MTES/DMDES co-precursor, not only allowed relatively low shrinkage in APD process, but also lowered the cross-linking density of the gel network, endowing the hybrid aerogels with macroporous structure and thus flexibility. The MTES/DMDES hybrid silica aerogels were prepared without using any surfactant.A two-step acid/base catalyzed sol-gel process was applied to control the phase separation of MTES/DMDES co-precursor in polar solvent Ethanol.Some basic concepts and theories in organic polymerization, such as the average functionality and Carothers equation, were adopted to discuss the reactive mode of MTES/DMDES co-precursor.The MTES/DMDES hybrid silica aerogels endured ambient pressure drying process, and still displayed favourable mechanical property.