Redox Responsive Sol-Gel Transition: A New Concept for Continuous Spinning of High-Performance and Recyclable Aerogel Fibers

Aerogel fibers are a new kind of fibrous materials with high porosity and low thermal conductivity, which hold great promise in applications of thermal insulation and personal protection. However, the great differences in mechanisms of gel transformation and fiber spinning, the contradiction between spinnability of spinning solution and crosslinking structure of the gel network, and the difficulty in balancing the key properties of fiber have significantly limited the practical applications of aerogel fibers. Herein, we report a novel "redox-responsive sol-gel transition spinning" method for the continuous spinning of polybenzimidazole/cobalt ion (Co) aerogel fibers, which utilizes the coordination property changes of imidazole ligands and Co with different redox states. The weak coordination interaction between imidazole and Co2+ endows the polybenzimidazole/Co2+ solution with good fluidity and spinnability, while the rapid and uniform oxidation of imidazole/Co2+ to strong imidazole/Co3+ complex in the spinning process allows the construction of a robust crosslinked network. Aerogel fibers obtained with optimal synthetic parameters demonstrate the homogeneous microporous structure in both internal and surface, high mechanical strength, low thermal conductivity, excellent thermal stability, and flame resistance. Furthermore, stretching treatment of organogel fibers prior to drying significantly improves the mechanical properties of aerogel fibers with strength as high as 240.6 MPa. These properties make the aerogel fibers promising for protection applications under extreme environments. The non-covalent crosslinking also permits the recycling of aerogel fibers by dissociation and reconstruction of the coordination bonds. This work is expected to provide a facile approach for continuous spinning of high-performance and recyclable aerogel fibers.