Double-cross-linking strategy for preparing flexible, robust, and multifunctional polyimide aerogel

Polymer-based aerogels have many uses because they possess excellent mechanical properties, such as high moduli and remarkable fatigue resistances. Freeze drying is an appealing aerogel preparation method because it is simple, green and inexpensive. However, polymer-based aerogels prepared by freeze drying always exhibit inferior mechanical properties compared to those prepared by classic supercritical drying, even if the raw material is polyimide. Herein, we report a novel double-cross-linking strategy to obtain a freeze-dried and robust polyimide/reduce graphene oxide/cobalt (PI/rGO/Co) aerogel with an interdigitated cellular architecture. The double-cross-linking strategy was attributed to hydrogen bonds derived from the graphene oxide (GO sheets) and coordination interactions from the Co ions. The interdigitated cellular architecture is the critical factor for achieving aerogels with low densities, flexibilities, high moduli (0.506 MPa compression modulus, 43% improvement of tensile modulus), and high fatigue resistances (1000 cycles). The as-prepared aerogel could be modified to achieve hydrophobicity with a 146.1° water contact angle. It was also difficult to be ignited and it exhibited excellent heat stability and low thermal conductivities (0.040 W·m−1·K−1 at 25 °C; 0.046 W·m−1·K−1 at 100 °C).