Aramid aerogel fibers with a radially heterogeneous structure fabricated via sequential coagulation and stretching for enhanced mechanical robustness and thermal insulation

Aramid aerogel fibers (AAF), which combine the inherent strength and thermal stability of aramid with the high porosity and low thermal conductivity of aerogels, represent promising candidates for lightweight thermal management textiles. However, current AAF often encounter limitations between mechanical robustness and thermal insulation due to their homogeneous porous structure. Herein, the AAF with radially heterogeneous structure (AAF-RHS) are fabricated by double-bath wet spinning and two-step stretching. Molecular dynamics (MD) simulations reveal that a balanced proton-transfer microenvironment can suppress acid self-association, and favorable for efficient aramid surface re-protonation and interchain association. The obtained AAF exhibit a large specific surface area of 279.47 m 2 /g, a low density of 0.115 g/cm 3 , a high specific strength of 157.17 (kN·m)/kg, a high porosity of 92.02%, and a low thermal conductivity of 32.1 mW/(m·K). Furthermore, the excellent chemical resistance, cryogenic flexibility at −196 °C, tunable hydrophobicity, and stable thermal insulation performance at both single-fiber and fabric levels are demonstrated. This work offers a structural design strategy for high-performance aerogel fibers toward advanced wearable thermal management applications.