Facile Fabrication of Anisotropic Chitosan Aerogel with Hydrophobicity and Thermal Superinsulation for Advanced Thermal Management

Traditional isotropic thermal insulators have been unable to meet the increasing demand for thermal insulation and the requirement of sustainable development, hence exploring a novel and advanced thermal management material is urgent. Previous studies indicated that the anisotropic porous materials with hierarchically aligned porous structures could improve the thermal management capability; however, the relationship between thermal properties and structure is unclear. Herein, a lightweight, large-scale, elastic, and anisotropic chitosan aerogel with excellent thermal management capability was fabricated via unidirectional freeze casting and silylation modification. Theoretical calculation had been used to analyze the effect of microstructure on the mechanical and thermal properties, as well as the anisotropic heat-transfer behavior. The anisotropic chitosan aerogel exhibited a honeycomb-like porous and lamellar structure, resulting in an advanced thermal management capability with a lower radial thermal conductivity (30.4 mW m–1 K–1) and two times higher axial thermal conductivity (60.1 mW m–1 K–1). The calculated results demonstrated that the thermal management capability of anisotropic chitosan aerogel was better than that of the isotropic materials (thermal conductivities of 10 and 22 mW m–1 K–1). It is helpful for further design of biopolymer aerogels for thermal superinsulation applications.