Flexible, Strong, Multifunctional Graphene Oxide/Silica-Based Composite Aerogels via a Double-Cross-Linked Network Approach.

Multifunctional silica-based aerogels are an emerging material due to their unique properties and wide applications. However, their large-scale production and application are limited due to the high cost and cumbersome preparation process. Herein, we prepare graphene oxide (GO)/silica-based composite aerogels via a simple in situ sol-gel reaction. GO nanosheets (GOs) are functionalized with polyethylenimine (PEI) and 3-glycidyloxypropyltrimethoxysilane (GPTMS) successively. After a cohydrolysis and condensation of trimethoxymethylsilane (MTMS) and dimethoxydimethylsilane (DMDMS) in the presence of GOs and a convenient ambient-pressure drying process, the composite aerogels are obtained. In addition to the normal cross-linking of MTMS and DMDMS, the GOs also behave as cross-linking points to significantly enhance the mechanical properties and thermal stability of the network of the composite aerogels. The pore structure of the aerogels is tailored by varying the GO loads as well as its surface modification. The Young's modulus of a composite aerogel with a GO load of 0.5 wt % is about 5 times that for a neat polysiloxane aerogel, and the maximum degradation rate temperature is increased to over 90 °C. Compared with pure polysiloxane aerogel, the thermal insulation and flame resistance are also improved by a small addition of GOs. Moreover, GO/silica-based composite aerogels show stable piezo-resistive behavior. With the excellent mechanical properties, thermal stability, and multifunctionality, GO/silica-based composite aerogels show promising applications under some harsh and extreme conditions.