Asymmetric gradient-structured PPy@bacterial nanocellulose aerogels enable broadband microwave absorption via synergistic polarization-conduction loss

The high carrier mobility of conductive polymers/polypyrrole (PPy) exhibits an inherent antagonism with the dielectric polarization loss required for microwave absorption materials. The excessively continuous electron transport in traditional PPy conductive networks leads to dominant electromagnetic wave reflection, rendering effective absorption challenging. The design of microstructures to reconstruct electron transport pathways in PPy while maintaining moderate conductivity and introducing controlled defects and polarization centers remains a significant challenge in achieving the functional transition from conductive loss to dielectric loss. This study addresses this by precisely constructing heterointerfaces through in-situ confined polymerization, achieving molecular coupling between bacterial nanocellulose (BNC) and PPy. This approach transcends the limitation of traditional conductive polymers with single shielding functions, enabling intelligent conversion of PPy-based materials from electromagnetic shielding to microwave absorption. By designing an asymmetric gradient structure, the composites achieve a minimum reflection loss (RL min ) of −53 dB at a thickness of 4 mm and an effective absorption bandwidth (EAB) covering the entire X-band (8.2–12.4 GHz) at 3.57 mm, a synergistic regulation paradigm of structure-composition-dielectric properties is established. Meanwhile, the fabricated aerogel maintains robust microwave absorption performance under acidic, alkaline, and high-temperature conditions, demonstrating exceptional environmental stability. This work provides a viable and sustainable strategy for developing green electromagnetic absorption materials, offering insights into balancing conductivity and polarization loss in conductive polymer systems to achieve efficient microwave dissipation.