Regulating the Dielectric Behavior of Conductive Polymers Through Vapor Phase Infiltration for Tunable Microwave Absorption

Conductive polymers have emerged as promising candidates for microwave absorbing materials due to their low density, structural flexibility, and tunable dielectric properties. However, persistent challenges such as conductivity decline, interfacial instability, and insufficient intrinsic loss capability dramatically limit the potential. Herein, vapor phase infiltration (VPI) is reported for the first time as a general interfacial engineering strategy for conductive polymer absorbers, enabling simultaneous regulation of dielectric behavior and enhancement of environmental stability. By infiltrating AlO _x into the in situ polymerized polypyrrole layer on polyurethane foams, the VPI process establishes a gradient hybrid interface from the aluminum‐rich surface to the moderately hybridized interior, which facilitates charge transport through interconnected pathways and promotes stability by optimizing stress distribution. The VPI‐modified foam exhibits enhanced absorption efficiency per unit thickness (~2.6 times that of the pristine foam) and achieves continuous frequency tuning (from S to Ku bands) and “on/off” function under compressive strain (0–70%) while also maintaining stable performance after prolonged acid/alkaline corrosion or continuous mechanical compression. Theoretical analysis reveals that the mechanism for enhanced polarization loss originates from a reorganization of charge density and bandgap narrowing at the VPI‐induced interface. This study provides guidance for designing high‐performance polymer‐based microwave absorbers and highlights the critical role of atomic‐level interface engineering in electromagnetic wave dissipation.