Fabrication of polyimide aerogels for daylighting windows: high transmittance, thermal insulation and lightweight

The harsh conditions on the high-altitude localities present considerable challenges for the development of architectural daylighting windows. Polyimide (PI) aerogels, with their notable mechanical strength, thermal stability, ultraviolet (UV) shielding capacity, and low thermal conductivity, emerge as a promising material candidate for such high-altitude fenestration applications. However, their currently limited optical transmittance hinders practical implementation in this context. Here, 2,2′-dimethylbenzidine (DMBZ) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) are used as monomers, and 1,3,5-Tris(4-aminophenoxy)benzene (TAB) as the crosslinker. The pyridine (PY)/triethylamine (TEA) catalysts are introduced to adjust pores for preparing high transmittance PI aerogels. The results show that as the proportion of TEA increases, the pore structure of the PI aerogel transforms from a compact morphology to a more porous one, while the average mesopore diameter significantly decreases, thereby reducing Rayleigh scattering. Under conditions using only TEA, the light transmittance at 750 nm is significantly increased to over 85%, while maintaining excellent UV protection. The thermal conductivity of this material is below 0.038 W m −1  K −1 , demonstrating excellent thermal insulation properties. Notably, the PI aerogel demonstrates an outstanding balance between mechanical robustness and ultra-low density, offering distinct advantages for weight-sensitive applications. This material presents an innovative solution for thermal management and UV shielding in daylighting windows, and also offers potential for applications such as lunar base glazing systems, polar structures, and agricultural greenhouses.