Diffusion of Ions in a Surface Chemically-Modified Polyimide

Abstract

The polyimide, PMDA-ODA, can be surface (sub-surface) modified by base hydrolysis followed by protonation to leave a thin film of polyamic acid over a fully cured polyimide. The hydrolysis/acidification scheme leaves the modified polyimide with a layer rich in carboxylic acid (and amide) groups. The carboxylic acid groups are effective in complexing ions from aqueous solution. In particular, the complexation of sodium and palladium ions has been examined. When in contact with an aqueous electrolyte solution, the palladium-complexed modified polyimide is subject to ion exchange. The kinetics of ion exchange between palladium and a sodium ion-containing electrolyte solution have been investigated. The exchange process is slow and appears to be diffusion-controlled.