Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE 3D nanofiber-assembled polyimide aerogels were fabricated via a facile strategy involving electrospinning, thermal imidization, and gas-foaming-induced expansion. The resulting aerogels feature a superlight hierarchical structure with exceptional thermal insulation properties, providing an efficient solution for thermal protection in extreme environments.

ABSTRACT
A template-free, freestanding three-dimensional polyimide (PI) nanofiber aerogel was fabricated via the synergistic integration of electrospinning with gas foaming. Electrospun PI membranes were foamed at room temperature in NaBH4/methanol, wherein released H2 bubbles uniformly expanded the fiber network into a hierarchically porous lamellar architecture. NaBH4 concentration (0.1–0.9 M) and foaming time (5–25 min) were systematically varied to elucidate their influence on aerogel architecture and properties. This foaming process primarily induces physical reorganization of the nanofibers without compromising their intrinsic chemical structure. The resulting aerogels exhibit densities of 2.11–3.52 mg/cm3, porosity > 95%, thermal conductivity 27.30–37.96 mW/m K (approaching that of air), and outstanding mechanical robustness and thermal stability, offering a lightweight, high-performance thermal-insulation platform for aerospace, cryogenic pipelines, and flexible electronics.