Hydro/Organo/Ionogels: “Controllable” Electromagnetic Wave Absorbers

Abstract Demand for electromagnetic wave (EMW) absorbers continues to increase with technological advances in wearable electronics and military applications. In this study, a new strategy to overcome the drawbacks of current absorbers by employing the co‐contribution of functional polymer frameworks and liquids with strong EMW absorption properties is proposed. Strongly polar water, dimethyl sulfoxide/water mixtures, and highly conductive 1‐ethyl‐3‐methylimidazolium ethyl sulfate ([EMI][ES]) are immobilized in dielectrically inert polymer networks to form different classes of gels (hydrogels, organogels, and ionogels). These gels demonstrate a high correlation between their dielectric properties and polarity/ionic conductivity/non‐covalent interaction of immobilized liquids. Thus, the EMW absorption performances of the gels can be precisely tuned over a wide range due to the diversity and stability of the liquids. The prepared hydrogels show good shielding performance (shielding efficiency > 20 dB) due to the high dielectric constants, while organogels with moderate attenuation ability and impedance matching achieve full‐wave absorption in X‐band (8.2–12.4 GHz) at 2.5 ± 0.5 mm. The ionogels also offer a wide effective absorption bandwidth (10.79–16.38 GHz at 2.2 mm) via prominent ionic conduction loss. In short, this work provides a conceptually novel platform to develop high‐efficient, customizable, and low‐cost functional absorbers.