Keywords:Silica aerogel, Molecular Dynamics, ReaxFF
In order to identify origin of flexibility of inorganic-organic hybrid aerogels, mechanical response and network deformation were examined by using reactive molecular dynamics simulations. In this work, three kinds of polymers, such as tetramethoxysilane (TMOS), methyl-trimethoxysilane (MTMS) and 1,2-bis(methyldiethoxysilyl)ethane (BMDEE), were constructed by polymerization simulations from the monomers by the reactive force field (ReaxFF) model. Stress-strain curve of compression-stretch cyclic loading/unloading behaves large hysteresis for TMOS, while MTMS has smaller hysteresis. Further, the loop of BMDEE maintains almost zero stress on the recovering deformation, indicating that BMDEE is obviously easy to be restored from the pressed structure. Micro-structure analyses, such as Si-O bond order, O-Si-O angle, Qn and ring size distributions, clearly demonstrate that network in BMDEE is not damaged by compressive deformation owing to both absence of rigid network composed of tetrahedral SiO4 and organic connections by -CH2CH2- unit.