Hierarchically porous polyimide/graphene aerogels with superior compressibility and electromagnetic interference shielding performance†

Abstract

The advancement of highly efficient electromagnetic shielding materials that are flexible, light weight and compressible is of paramount importance in applications ranging from aerospace to flexible electronics. However, the trade-off between electromagnetic interference shielding effectiveness (EMI SE) and mechanical properties caused by conductive fillers in conductive polymer composites yet continue to encounter significant challenges. In this study, a dual-template strategy (ice-templating and sacrificial templating) was carried out during freeze-drying to fabricate polyimide/graphene aerogels with hierarchically open pore architectures, where the flexible and mechanically robust polyimide acted as the matrix and graphene acted as the conductive filler. Consequently, the comparable sizes between rigid graphene and sacrificial spheres produced extensive open pores. The resultant aerogel exhibited a porosity of 96.2%, an electrical conductivity of 1.85 S m⁻¹, and a density of 0.05 g cm⁻³. Furthermore, its distinctive hierarchically open pore structure conferred an EMI SE of 48.3 dB and a specific EMI SE of 1932 dB cm² g⁻¹, possibly owing to enhanced internal multiple reflections. Notably, the aerogel demonstrated remarkable flexibility and can withstand cyclic deformation, exhibiting a compressive strength of 108.8 kPa at 30% strain while maintaining a low modulus of 41.3 kPa. Its superior shock absorption and energy dissipation capabilities were further exemplified by protecting a quail egg from damage when dropped from a significant height, underscoring its high potential for applications in flexible electronics and intelligent manufacturing.