Bio-inspired covalent crosslink of aramid nanofibers film for improved mechanical performances

In aramid nanofiber (ANF) films, the chemical interactions between individual fibers are mainly hydrogen bonds that formed in C=O and N-H, which are highly ordered and ensure the high strength and modulus of ANF paper. In this work, the ANF is firstly hydrolyzed in NaOH aqueous solution to realize carboxylation. Subsequently, the carboxylated ANF is covalently crosslinked by bio-inspired polydopamine (PDA) and assembled to be a paper-like film through vacuum filtration. Compared to pure ANF and un-crosslinked PDA-ANF films, the covalently crosslinked composite film shows an improved mechanical strength and toughness simultaneously. This indicates that the covalent bonds are more useful than hydrogen bonds on improving the mechanical properties of ANF paper.