Synthesis of porous polyimide films with low dielectric constant and excellent mechanical properties by ambient pressure drying

• Published in: Journal of materials science Vol. 57; no. 20; pp. 9480 - 9492
• Main Authors: Ding, Chengcheng, Li, Ruiyi, Yu, Juan, Wang, Xiaodong, Huang, Pei
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2022; Springer; Springer Nature B.V
• Subjects: Aerogels; ambient pressure; ambient temperature; Bulk density; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Crystallography and Scattering Methods; Dielectric properties; Dielectrics; Electric properties; Electrical conductivity; Fourier transform infrared spectroscopy; Fourier transforms; Freeze drying; Infrared spectra; Materials Science; Mechanical properties; Molecular chains; nanopores; Permittivity; Polyimide resins; Polymer Sciences; polymers; Polymers & Biopolymers; Pore size; porosity; Pressure; Room temperature; Solid Mechanics; strength (mechanics)
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-021-06792-3

Polyimide aerogels are high-performance polymer materials, but they have been restricted by costly drying and low mechanical strength in practical applications. Here, we report a family of porous polyimide (PI) aerogel films prepared through a partial pre-imidization process under ambient pressure drying and freeze-drying. The effect of pre-imidization degree (pre-ID) on the mechanical and dielectric properties of porous films was investigated in detail. The Fourier transform infrared spectra show that the partial pre-imidization process made the molecular chain with coexisted amide acid and imide rings. The porous structure of film was successfully controlled by adjusting the pre-ID, which was confirmed by pore size distributions. These aerogel films with nanoporous structures exhibit better mechanical properties (e.g., 10.61 MPa at 0.433 g cm −3 at room temperature) and lower dielectric constant (minimum of 1.414 at 10 6  Hz) over the entire bulk density range (0.398–0.5 g cm −3 ). Their morphology, pore characteristics, and properties were similar, whether by ambient pressure drying or freeze-drying. Moreover, this work will provide a new perspective on the fabrication of porous PI aerogel film via ambient pressure drying with efficient processability. Graphical abstract