Hydrogen bonds-induced conduction loss for enhanced electromagnetic attenuation in deep eutectic gel absorber

Gels and conductive polymer composites including hydrogen bonds (HB) have developed into promising electromagnetic wave (EMW) absorption materials in response to different application scenarios. However, the relationship between conduction loss in EMW absorbing materials and charge transfer in HB remains to be explored. Herein, we construct a series of deep eutectic gels for fine-tuning the quantity of HB, by adjusting the ratio of choline chloride (ChCl) and ethylene glycol (EG). Due to the characteristics of deep eutectic gels, the impact of magnetic loss and polarization loss on EMW attenuation can be disregarded. The results indicate the quantity of HB increased first and then decreased with the introduction of EG, and HB-induced conductive loss exhibits similar patterns. At a ChCl and EG ratio of 2.4, G22-CE2.4 demonstrates the best EMW absorption performance (effective absorption bandwidth=8.50 GHz, thickness=2.54mm), which is attributable to the synergistic effects of excellent conductive loss and impedance matching generated by the appropriate number of HB. This work clarifies the role of HB in dielectric loss for the first time and offers a generic insight into the optimal design of supramolecular polymer absorbers.