Controllable Ultrathin Thickness of Carbon Nanotubes Layers and Ultralow Equivalent Content in Alternating PMMA‐Based Nanocomposites for Optimized Impedance Matching to Achieve Wideband Electromagnetic Absorption

Abstract Traditional polymer‐based nanocomposites for electromagnetic wave absorption (EMWA) often require high filler content, which limits their mechanical durability and practical applications. In this study, a novel strategy is proposed, meticulously designed and fabricated using an innovative exponential unit stacking approach, to construct an alternating structure in polymethylmethacrylate (PMMA)/carbon nanotubes (CNTs) nanocomposites, achieving “two birds, one stone” benefits: precise controlling of ultrathin thickness of CNTs layers and ultralow equivalent content for high‐performance EMWA. Notably, with a macroscopic thickness of 2.0 mm and an equivalent CNTs mass fraction of 1 wt.%, the 64‐unit structure sample features ultrathin PMMA/CNTs (CNTs) layers of 1 µm, achieving a minimal reflection loss value of −17.33 dB and an effective absorption bandwidth value of 1.28 GHz at the X‐band, significantly outperforming the single‐unit structure sample with an RL _min of −4.19 dB and no EAB. Both theoretical simulations and experimental results demonstrate that the enhanced EMWA performance is attributed to optimized impedance matching, even with ultrathin CNTs layers and ultralow filler content by constructing an alternating structure. This strategy, rooted in heterostructure interface engineering, achieves wideband EMWA while constructing a robust multilayer film stack, paves the way for advanced and cost‐effective applications in electromagnetic protection.