| Summary: | In order to prepare flexible glass cover sheet materials suitable for space solar cells, fluorinated diamine 2,2’-bistrifluoromethyl benzidine (TFDB) and fluorinated dianhydride 4,4’ (hexafluoroisopropyl) diphthalic dianhydride (6FDA) as the monomer, polyimide (PI)/SiO<sub>2</sub> composite film was synthesized by in situ polymerization, and the influence of coupling agent and SiO<sub>2</sub> nanoparticle content on the film structure and properties was studied. The results show that PI synthesized from fluorine-containing monomers has better light transmittance, and the highest transmittance can reach 91.4%. The average visible light transmittance of the composite film decreases with the increase of SiO<sub>2</sub> content, and the transmittance of the film decreases less in the high-wavelength region and greatly decreases in the low-wavelength region. The tensile strength and elastic modulus of PI/SiO<sub>2</sub> composite film increase with the increase of SiO<sub>2</sub> content, first increase and then decrease, reaching the maximum when the content is 10%; while the elongation at break of the composite film gradually increases with the increase of SiO<sub>2</sub> content reduce. The thermal stability of PI/SiO<sub>2</sub> composite film increases with the increase of SiO<sub>2</sub> content. The doping of nano-SiO<sub>2</sub> significantly suppresses the influence of irradiation on the mechanical properties of the film.
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