Antibacterial and mildew‐proof aramid fiber III: The chlorination mechanism through experimental and computational investigation

Abstract Heterocyclic aramid fiber (Aramid III) is an important member of the aromatic polyamide family, featured as high strength, modulus, and thermal stability. However, the erosion by microorganisms severely jeopardizes these intrinsic properties. In this study, antibacterial and mildew‐proof Aramid III was facilely prepared via chlorination, which exhibited excellent bactericidal ability (100% bactericidal rate at 10 4 CFU/mL) against various microorganisms while experiencing only a slight decrease (less than 1%) in mechanical and thermal properties. Furthermore, Density Functional theory (DFT) calculations of the chlorination process and NMR spectra of the model molecule BPB revealed that the preferential chlorination sites were the NH bonds on the benzimidazole ring rather than those on amide group, and a cation reaction mechanism was initially proposed based on the differences in activation energy for various reaction pathways. The antibacterial and mildew‐proof functionalization in the present study may effectively prolong the service time of Aramid III, and the revealed chlorination mechanism may provide a reference for other halamine polymers.