Attaining Broadband and Enhanced Microwave Absorption in <scp>PANI</scp>: Effect of Reaction Media and Morphology

ABSTRACT A comprehensive investigation into the microwave absorption properties of polyaniline (PANI) synthesized using distinct reaction media: water (PANI‐Aq), hydrochloric acid (PANI‐HCl), and citric acid (PANI‐CA) was systematically performed. Morphological analysis revealed diverse nanostructures: PANI‐Aq exhibited nanosheets interspersed with nanorods, PANI‐HCl showed a granular morphology, and PANI‐CA displayed well‐aligned nanotubes. Structural characterization via XRD and FTIR confirmed the successful synthesis of PANI in different forms, highlighting variations in the crystallinity and oxidation states that were consistent with their respective morphologies. Comparatively, the PANI‐CA nanotubes with highly aligned structures provided a continuous charge transport pathway and enhanced charge delocalization, leading to superior conductivity. The significant aspect ratio and high surface area of the conductive nanotubes in PANI‐CA contributed to the strong conduction loss, interfacial polarization, dipole polarization, and improved impedance matching. As a result, 20% PANI‐CA in paraffin wax exhibited outstanding microwave absorption properties, achieving a minimum reflection loss (RL min ) of −34.89 dB at 3 mm thickness with an excellent effective absorption bandwidth (EAB) of 3.44 GHz in the X‐band frequency range.