Hot-Pressing/Salt-Leaching Method Assisted by Boronic Ester Dynamic Bond to Prepare Vitrimer Foams with Ultra-Low Relative Permittivity and Superhydrophobic Performance

Ultra-low dielectric foams (ULDFs) have found important use in antennas and wave transparent devices. However, the controlled preparation of ULDFs is still a big challenge. In this work, a boronic ester bond-assisted hot-pressing/salt-leaching (BHS) method is proposed to generate interconnected pore structure with tunable porosity and performance. In detail, styrene resin vitrimer is prepared with boronic ester cross-linked network (BESR) which possessed low dielectric constant of 2.70, high modulus of 385 MPa, and reprocessability. BESR vitrimer exhibited drastically enhanced processability at the temperature > T v (160 °C). Thanks to this unique feature, BESR vitrimer foams can be fabricated by hot-pressing with salt particles followed by salt leaching. Such vitrimer foams exhibited advantageous pore-forming processability, fabrication efficiency, and pore stability over conventional polymeric foams. The low extreme of dielectric constant can reach 1.60. Furthermore, owing to interconnected pore structure, superhydrophobic foam (water contact angel (CA) ≈ 154°) is facilely fabricated on the basis of BESR to afford anti-icing performance. The BESR foam can maintain its superhydrophobicity underwater flow impacting at 10 kPa pressure, showing advantageous high durability. BESR foams also have good recyclability and would be potentially applied in recyclable antennas.