Reflective and conductive silvered polyimide films for space applications prepared via a novel single-stage self-metallization technique

Highly reflective and surface conductive flexible polyimide films have been prepared by the incorporation of silver(I) acetate and 1,1,1-trifluoro-2,4-pentanedione into a dimethylacetamide solution of poly(amic acid), formed from 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride and 4,4′-oxydianiline. Thermal curing of the silver(I)-containing poly(amic acid) leads to cycloimidization of the polyimide precursor with concomitant silver(I) reduction yielding a reflective and conductive silvered surface with properties approaching those of the native metal. Ligand/anion effects on the metallization process resulted when using additional silver(I) compounds including: silver(I) nitrate; silver(I) tetrafluoroborate; (trifluoroacetato)silver(I); (hexafluoroacetylacetonato)silver(I); (trifluoroacetylacetonato)silver(I); and 1-(2-thienyl)-3,3,3(trifluoroacetonato)silver(I). Comparisons among these six silver(I) compounds as precursors for the surface metallization of BTDA/4,4′–ODA are discussed with regard to reflectivity, conductivity and surface morphology. The metallized films usually retain the essential mechanical properties and thermal properties of a parent film. Films were characterized by X-ray diffraction, transmission and scanning electron microscopy, tapping mode atomic force microscopy and X-ray photoelectron spectroscopy. Also, electrical conductivity, reflectivity, differential scanning calorimetric, thermal gravimetric and mechanical measurements were made on the metallized films.