Cross-linked Polyimide Nanofibrous Aerogels with Hierarchical Cellular Structure for Thermal Insulation
Khanh-Van Thi Khuat, Hoan Ngoc Doan, Phu Phong Vo, Masaki Negoro, Kenji Kinashi, Kazuyoshi Kanamori, Wataru Sakai, Naoto Tsutsumi
Abstract
Due to their low bulk density, high porosity, and functional performance, aerogels are ideal candidates for a variety of applications. However, their potential application in a variety of fields is limited by their time-consuming and costly complex fabrication process. In this study, electrospun 3-aminopropyltriethoxysilane-grafted polyimide (PI@APTES) nanofibers were used to construct nanofibrous aerogels (NFAs) via freeze-drying a dispersion of cross-linked-PI short fibers and a binder (PI@APTES), resulting in improved properties and functionalities. A highly siloxane cross-linked network structure was formed by hydrolysis and condensation reactions to generate stable nanofibrous aerogels. The obtained polyimide nanofibrous aerogels (PiNFAs) had a hierarchically three-dimensional (3D) microporous structure, high porosity (over 98%), tunable densities (10.6 ± 0.7–13.6 ± 0.2 mg cm –3 ), solvent resistance, superhydrophobicity (water contact angle over 163°), low thermal conductivity (as low as 33.2 mW m –1 K –1 ), and mechanical stability. These PiNFAs are promising candidates for potential applications in thermal insulation, lightweight construction, filtration, and sensors.