Hierarchical Design of 1D Building Blocks for Anisotropic Aerogel

Abstract The structural integrity and continuity are prerequisites for exploiting the performance advantages of aerogels, while limitations in mechanical properties, such as low strength, high brittleness, and poor processability confine fully intact aerogels to laboratory settings. Here, a composite aerogel SPCCAM designed with hierarchical structuring into 1D building blocks at the nanoscale and honeycomb‐like anisotropic architecture at the microscale is presented. The inner carboxylated cellulose nanofiber core (CNFs‐C) exhibits much higher strength than the intermediate polybenzoxazine (PBOZ) shell, and the interface is highly reinforced by a crosslinked network of amino and hydrogen bonds, forming a highly stable 1D building block. Superhydrophobic SiO 2 nanoparticle (hydrophobic‐260) is discretely distributed on the outer surface of the PBOZ shell, resulting in a nanoscale lotus leaf effect. Thus, the SPCCAM demonstrates outstanding properties including ultrahigh strength, excellent deformability and fatigue resistance, good machinability, ultralow thermal conductivity and coefficient of linear expansion, and superhydrophobicity from the inside out and long‐term hydrophobic stability along the radial direction of microscale channels, defining a novel method for designing aerogels with superior integrated mechanical, thermal insulation, and hydrophobic properties, and offering an attractive solution for high‐efficiency thermal insulators in high‐moisture extreme environments, such as deep‐sea and polar regions.