Carbonization of aromatic polyimides and pore development in carbon films

Imidization and carbonization behaviors of various aromatic polyimide films synthesized from an anhydride with different diamines were investigated by FTIR and TG/DTG methods. Imidization of poly (amic acid) s with pendant -CH3 and-CF3 groups directly bonded to phenyl ring required long times for curing at 300°C. Pyrolysis and carbonization of polyimides having pendant groups occurred over a little wider temperature range than those having no pendant groups. The carbonize films were of ultramicroporous character with pore width of ca. 0.5 nm. Pore development in carbon films was found to depend strongly on whether the precursor polyimide contains fluorine or not ; fluorine containing polyimide gave a high microporous surface area of 1400 m2/g and micropore volume of 0.39 mL/g.