Cross‐Scale Interface Engineering for Fabricating Super‐Strong and Super‐Tough Aramid nanofiber film

Abstract Poly (p‐phenylene terephthalamide) (PPTA), known for its exceptional mechanical properties under the brand name Kevlar, finds extensive use in high‐performance applications despite the challenges it presents in processing and integration with other materials. Existing top–down methods for preparing PPTA composites result in significantly reduced strength (<200 MPa) and toughness (<10 MJ·m − 3 ) due to insufficient interfacial interactions, limiting their application. Here, a cross‐scale interface engineering strategy is reported for fabricating super‐strong and super‐tough PPTA composite films. At the microscale, a synergistic crosslinking strategy of physical entanglement and hydrogen bonding to crosslink PPTA nanofibers is employed. At the macroscale, the network using a cyclic freeze–thaw and the stretch‐drying method is reinforced. The PPTA nanofiber composite film is super‐strong (854.6 MPa), super‐tough (106.2 MJ·m − 3 ), and has a high‐temperature resistance (300 °C). Moreover, the bottom–up approach enables the direct synthesis of PPTA nanofibers, significantly reducing the preparation time from 7 days to 0.5 h. Furthermore, it is demonstrated that the composite film can be integrated into a robust and intelligent sensing‐display device that responds to external mechanical and heat injuries for firefighter's protection. This work provides an efficient strategy for fabricating high‐performance PPTA composites, paving the way for their practical use as durable protective materials.