Covalent Bonds Reinforced Strength and Modulus of Heterocyclic Aramid Fiber by Interfacial Aminated‐MXene Nanosheets

Architecting high-performance heterocyclic poly(p-phenylene benzimidazole-benzamide) (PBIA) fiber presents challenges, including low orientation, crystallinity and interchain interaction, which reduces mechanical property. Herein, for the first time, we develop covalent bonds strategy to reinforce the mechanical property of PBIA fiber by using interfacial aminated-MXene (MXene-NH₂) nanosheets via in situ polymerization and microfluidic spinning. The MXene-NH₂ with reactive amino sites can serve as nucleating agents and chain anchors to enhance orientation, crystallinity and interchain interaction via strong interfacial amido covalent bonds. Consequently, the representative PBIA/Ti₃C₂T_x-NH₂ fiber exhibits the increase of 34% in tensile strength and 18% in Young's modulus, with an ultrahigh tensile strength of 6.95 ± 0.16 GPa and Young's modulus of 273.6 ± 5.1 GPa. This covalent bonds reinforced mechanism can be further extended to other MXene-NH₂ nanosheets, such as V₂CT_x-NH₂, Nb₂CT_x-NH₂ and Mo₂TiC₂T_x-NH₂, indicating the universality. Benefiting from ultrahigh strength and modulus, the PBIA/Ti₃C₂T_x-NH₂ fiber can maintain 61% initial strength after 0.8 J transverse impact, and the CNTs@PBIA/Ti₃C₂T_x-NH₂ fiber supercapacitor presents durable capacitance under stretching state, indicating the promising paradigm for high-performance fiber as impact-protection and wearable supercapacitor.