| 초록 |
Herein, we investigated the effect of thermo-oxidative crosslinking of siloxanes on the C3H6/C3H8 separation performance of carbon molecular sieve (CMS) membranes derived from polymer blends containing a fluorine-containing polyimide and a ladder-structured polysilsesquioxane (PI/LPSQ). The PI/LPSQ precursors self-generated fluorinated gases, which possibly lead to cleavage of the double-stranded siloxanes during pyrolysis. At the same time, residual siloxanes underwent thermo-oxidative crosslinking, which resulted in the densification into nonporous inorganic SiO2 phases. Such impermeable SiO2 phases adversely affected the gas diffusion, decreasing C3H6 permeability, but contributed to the significant enhancement in the C3H6/C3H8 selectivity up to as much as 67 because of the substantially enhanced diffusivity selectivity. Density functional theory-based pore size distribution analysis exhibited that the modality of the pore distributions sharpened in the ultramicropore regime with increase in LPSQ content, supporting the enhancement in selectivity. |
