Harnessing the Molecular Interactions of Heterocyclic Aramids with Benzimidazole Units for Continuous Spinning of Robust and Recyclable Aerogel Fibers

Abstract

Aerogel fibers have attracted considerable attention due to their lightweight, stitchability, and heat-insulating properties, which are promising for wearable insulation applications. However, there is still a lack of a facile method to continuously spin high-performance aerogel fibers with uniform structure and excellent thermal/mechanical properties. This paper reports a continuous spinning of heterocyclic aramid aerogel fibers (HAAFs) by combining the principles of hydrochloric acid (HCl)-induced protonation and heat-induced reduction of solvation. The protonation of the benzimidazole ligand contained in the polymer backbone weakens the dissolving capacity of the polymer and extends the conformation of polymer chains, resulting in ordered and liquid-crystal-like aggregation structures, as evidenced by the increased birefringence in organogels, which is beneficial to improve the intermolecular interactions and strengths of gel networks. Heating of the solidification bath during spinning further reduces the solvation of the polymer and enhances the interaction between HCl and benzimidazole ligands, which strengthens the cross-linking network and forms robust gel fibers. The subsequently obtained HAAFs demonstrate a uniform porous structure, low thermal conductivity, high mechanical properties, high thermal stability, and good flame retardancy, making them good candidates for high-temperature thermal insulation applications. In addition, the HAAFs are also recyclable due to their reversible intermolecular interactions. This study is expected to provide an effective strategy for the design and large-scale manufacturing of aramids and other high-performance aerogel fibers.