Ultralight PDMS‐Based Aerogels for Electromagnetic‐Acoustic Wave Absorption in Harsh Environment

ABSTRACT Polydimethylsiloxane (PDMS) exhibits multiphysical responsiveness, enabling versatile forms from coatings to foams that emphasize robustness and functionality. However, the development of ultralight PDMS‐based aerogels remains unexplored, particularly for systems demanding concurrent electromagnetic and acoustic wave absorption while withstanding challenges from harsh environment. Herein, we report a green and low‐cost dual‐template method, exploiting the complementary packing behaviors of fine salt and large sugar for the scalable and shape‐customizable fabrication of PDMS‐based aerogels. They exhibit ultralight weights ranging from 37.3 to 66.5 mg cm −3 , which breaks the density limit of traditional PDMS foams (≈100 mg cm −3 ). Based on the dielectric optimization of single‐walled carbon nanotubes (SWCNTs)/aramid fibers (AFs), as well as a highly adjustable multiscale porosity spanning from the nano to millimeter range, efficient absorption of electromagnetic energy (436.72 dB cm 3 g −1 of specific reflection loss and 84.21 GHz cm 3 g −1 of specific effective absorption bandwidth) and acoustic energy (noise reduction coefficient > 0.24) is achieved. Furthermore, the aerogels demonstrate exceptional capability in thermal insulation, flame retardancy, elastic recovery, hydrophobicity and corrosion resistance. This multifunctionality, combined with their ultralow density, positions SWCNTs/AFs/PDMS aerogels as promising candidates for lightweight and multifunctional protective layers or structural encapsulation components in aerospace and flexible electronic systems.