Acid-induced crystallization enables high-performance electromagnetic wave absorption via constructing rapid carrier transport channels

Based on the inherent dielectric properties of coal gangue (CG), developing it into a high-performance electromagnetic wave-absorbing material through functional compounding serves as an effective approach to synergistically advance the high-value utilization of coal-based solid waste and the mitigation of electromagnetic pollution. Among various materials, polyaniline (PANI) is widely used to construct composite due to its tunable conductivity. In such composite systems, the crystallinity of PANI directly affects the formation of charge carrier migration and conduction networks, which is a key factor in regulating its dielectric properties, particularly in enhancing conduction loss. In this study, in-situ polymerization technology was employed to precisely control the mixing ratio of doping acids, constructing a series of CG@PANI composites. Beyond providing H⁺ to protonate the quinoid nitrogen in PANI chains and create mobile charge carriers, the long-chain alkyl and benzene ring structures of the doping acids also function as key “structural directing agents”. By enhancing the π-π stacking interactions between the molecular structures of PANI, the molecular chains can be arranged in a more ordered manner, thereby regulating the crystallinity of PANI. The crystalline regions provide efficient pathways for the rapid migration of charge carriers, which ultimately improves the charge transport properties. The results indicated that the suitable crystallinity-induced two-dimensional lamellar structure favors the formation of a more complete conductive network to enhance conduction loss. Consequently, the optimized CP composite, with a thickness of 2.49 mm, exhibited a minimum reflection loss of −62.9 dB and an effective absorption bandwidth of 5.0 GHz. This study provides insights into the mechanism by which crystallinity regulates dielectric properties, while concurrently offering a novel strategy for the high-value utilization of CG.