Simple method for preparation of porous polyimide film with an ordered surface based on in situ self-assembly of polyamic acid and silica microspheres

In this Article, we addressed a facile method for the fabrication of porous polyimide film with an ordered surface based on the solvent-evaporation-assisted in situ self-assembly of polyamic acid (PAA, precursor of polyimide) and silica microspheres during vacuum-drying of PAA/silica colloid solution. Hydroxyl groups on the surface of silica microspheres have strong hydrogen-bonding with PAA chains, which improve the dispersion of silica microspheres in PAA/DMF solution and further help the self-assembly of PAA/silica colloid solution via solvent evaporation. The approach is simple, neither the preparation of special template nor complex preparation process and precise control over condition is necessary. Furthermore, the method could be employed for mass production of ordered porous polyimide films, and by changing the content and size of silica microspheres, the pore size and porous structure of the porous polyimide films could be tunable. The wettability behavior of the as-prepared porous polyimide films is also studied; the ordered surface topography of the porous polyimide films could change the wettability from hydrophilicity to hydrophobicity.