Methyl orange and pH-regulation guiding the polypyrrole nanotubes with ultralow filler loading achieve excellent microwave absorption performance

To address the issues of high filler content and poor wave absorption performance in single-component absorbers, we constructed tubular high-dielectric polypyrrole (PPy) through morphology control and doping, achieving high-performance microwave absorption at ultra-low filler content. This study utilized various surfactants for the oxidative polymerization of high-dielectric PPy (PPy-S X ) and its micromorphology was further optimized via pH regulation to further obtain excellent impedance matching of PPy (PPy-S 5 -X). Experimental results reveal that non-ionic surfactants, particularly methyl orange (MO), significantly improve the dielectric properties of tubular PPy (PPy-S 5 ). pH-regulation (from pH 1 to 11) markedly influences micromorphology. PPy-S 5 –5 (pH=5.0) possesses the most remarkable nanoparticle-nanotube morphology for impedance matching at ultralow filling content. With a thickness of 2 mm, PPy-S 5 –5 (5 wt% filling amount) exhibits an RL min of –40.88 dB with an effective absorption bandwidth of 5.04 GHz (10.24–15.28 GHz). By contrast, the RL min of PPy-S 5 –5 is over six times better than that of PPy-S 1 synthesized using cetyltrimethyl ammonium bromide (CTAB). This superior microwave absorption performance is due to enhanced electromagnetic wave loss for two main reasons: First, MO as a soft template promotes tubular PPy formation, allowing charges to continuously move and transfer between molecules to enhance conduction loss. Additionally, pH regulation optimizes particle distribution on PPy nanotubes, improving multi-interface interactions and interfacial polarization. This micromorphology regulation strategy of PPy unlocks its potential as a lightweight, efficient absorbent material, achieving superior absorption performance at low filling volumes in wave-absorbing applications.