Preparation of porous carbon films by the pyrolysis of poly(urethane-imide) films and their pore characteristics Original Research Article

Porous carbon films were prepared by the pyrolysis of poly(urethane-imide) films that were prepared by a reaction between phenol-terminated polyurethane prepolymer and poly(amide acid) obtained from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). Upon thermal treatment of the poly(urethane-imide) films at 300 to 400°C, the thermally less stable urethane domains decomposed, leaving porous polyimide films. The porous polyimide films were further pyrolyzed at 900°C for 1 h to give porous carbon films. The formation of macropores was confirmed from scanning electron microscopy (SEM) of the surface and the cross-section of the films. The size distribution of the macropore was relatively narrow. With the increase of urethane content, the size of the macropore increased. The average pore size was found to be controlled between 0.6 μm and 10 μm by changing the ratio of the imide and the urethane components. It was also revealed from nitrogen adsorption isotherms that macroporous carbon films also contain micropores that were formed during the pyrolysis of the polyimide films. The progress of the micropore formation was studied by measuring nitrogen adsorption isotherms of the carbonized films treated at various temperatures.