Hydrogen bond-induced conduction loss for enhanced electromagnetic attenuation in deep eutectic gel absorbers

Gels and conductive polymer composites, including hydrogen bonds (HBs), have emerged as promising materials for electromagnetic wave (EMW) absorption across various applications. However, the relationship between conduction loss in EMW-absorbing materials and charge transfer in HB remains to be fully understood. In this study, we developed a series of deep eutectic gels to fine-tune the quantity of HB by adjusting the molar ratio of choline chloride (ChCl) and ethylene glycol (EG). Owing to the unique properties of deep eutectic gels, the effects of magnetic loss and polarization loss on EMW attenuation can be disregarded. Our results indicate that the quantity of HB initially increases and then decreases with the introduction of EG, with HB-induced conductive loss following similar patterns. At a ChCl and EG molar ratio of 2.4, the gel labeled G22-CE2.4 exhibited the best EMW absorption performance, characterized by an effective absorption bandwidth of 8.50 GHz and a thickness of 2.54 mm. This superior performance is attributed to the synergistic effects of excellent conductive loss and impedance matching generated by the optimal number of HB. This work elucidates the role of HB in dielectric loss for the first time and provides valuable insights into the optimal design of supramolecular polymer absorbers.