Formation and characterization of cobalt oxide layers on polyimide films via surface modification and ion-exchange technique

Polyimide (PI) films with thin cobalt oxide (Co3O4) layers on both film sides have been prepared via a surface modification and ion-exchange technique. The method works by hydrolyzing the PI film surfaces in aqueous potassium hydroxide solution and incorporating Co2+ into the hydrolyzed layers of PI film via subsequent ion exchange, and followed by thermal treatment in ambient atmosphere. The PI composite films were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractions, scanning electron microscopy, transmission electron microscopy and thermogravimetric analyses, as well as surface resistance and mechanical measurements. By varying the absorbed cobalt ion content, a series of PI/Co3O4 composite films with insulative to semiconductive surfaces were obtained. The room temperature surface resistances of the semiconductive composite films reached to about 107 Ω. The Co3O4 particle formed on PI film surfaces was in the range of 10–40 nm. The final composite films maintained the essential mechanical properties and thermal stability of the pristine PI films. The adhesion between surface Co3O4 layers and PI matrix was acceptable.