Scalable ambient-dried aramid aerogel fibers with hierarchical networks for ultrahigh toughness and thermal insulation.

Achieving aerogel fibers that combine high porosity with mechanical robustness under ambient drying remains a long-standing challenge. Here, we present a proton-donor-assisted solvent-exchange strategy to fabricate hierarchically porous aramid nanofiber (ANF) aerogel fibers with 85.2% porosity and ultrahigh toughness (>9.3 MJ m-3). A suite of characterization and molecular dynamics simulations reveal that restoring hydrogen bonding between ANFs requires both reprotonation of poly(p-phenylene terephthalamide) and a nonpolar solvent environment to promote close chain packing. Introducing trace proton donors (e.g., water or citric acid) during solvent exchange is therefore essential to strengthen hydrogen bonding and stabilize ANF networks against capillary collapse. Furthermore, spatial heterogeneity in solvent composition, arising from proton-donor-induced solvent-solvent phase separation, creates a hierarchical pore architecture that enables multimodal mechanical energy dissipation, yielding simultaneously high tensile strength (>19.7 MPa) and unprecedented stretchability (>82%). The aerogel fiber-based textiles exhibit outstanding thermal insulation and resilience across cryogenic to high temperatures, offering a scalable pathway toward next-generation thermal-protective and impact-resistant aerogel textiles.