Cryogenic tolerant, flame retardant, and closed-loop recyclable adhesive for substrate-adaptive electromagnetic shielding

With the rapid increase in serious threats of electromagnetic interference, multilayer electromagnetic shielding composites (ML-ESCs) show broad prospects for preventing electromagnetic interference in green buildings, smart wearables, and aerospace. However, existing ML-ESCs suffer from poor cryogenic adhesion, non-flame-retardant substrates, and poor recyclability. Herein, we proposed an "interfacial cooperative adhesion factor system and dynamic reversible crosslinking" strategy to fabricate a multifunctional adhesive. The adhesive was constructed by employing a PTA dynamic covalent network as the backbone, wherein phytic acid (PA) and hexaphenoxycyclotriphosphazene (HPCTP) were introduced separately as hydrophilic and hydrophobic dynamic adhesion factors. The PA-HPCTP adhesion factor system endowed the adhesive with prominent multi-substrate adhesion adaptability, cryogenic adhesion durability, and flame-retardant performance. Moreover, the adhesive exhibited outstanding degradability in alkaline aqueous solution and efficient closed-loop recycling of TA and HPCTP, with both recovery rates exceeding 80%. Furthermore, the multifunctional adhesive was designed to construct diverse substrate-based sustainable ML-ESCs, including wood, textile fabric, glass, and carbon fiber, achieving the integration of high-efficiency electromagnetic shielding (up to 97.9 dB), extreme environmental tolerance, and multi-component closed-loop recycling of matrix monomers and substrates. This work provides new insights into the design of next-generation sustainable multifunctional polymer electromagnetic shielding composites.