Bioinspired Chestnut Burr-like Polyaniline: Achieving Superhydrophobicity and Excellent Microwave Transparency through Controlled Polymerization.

Achieving dual functionalities of hydrophobicity and excellent microwave transmission in a single material remains a significant challenge, especially for advanced applications in aerospace, telecommunications, and navigation engineering. Inspired by natural designs like chestnut burrs, bioinspired polyaniline (PANI) particles with tunable micro-/nanostructures through a facile template-free polymerization process have been developed. By regulating the polarity of the reaction system, temperature, and reaction time, various hierarchical structures, including cross-linked nanosheets, chestnut burr-like spheres, and starburst flower-like structures, are synthesized. The spiny projections and surface roughness endow the unique chestnut burr-like structure, achieving superior hydrophobicity and excellent microwave transmission properties. The formation of hierarchical structures is driven by intermolecular interactions during the nucleation and growth processes. The presence of both hydrophobic and hydrophilic domains within PANI particles leads to the coexistence of large water contact angles up to 152° and high surface energy. The optimized PANI structure minimizes the charge carrier mobility, dipole relaxation, and dielectric loss. A superior microwave transmission efficiency of up to 96% is achieved with these combined factors. By disclosing the relationship between the structure, wettability, and dielectric properties, a design protocol for the bionic regulation of micro-/nanostructures is established to achieve both superhydrophobic and excellent microwave-transparent functions.