FABRICATION OF HIGHLY REFLECTIVE COMPOSITE POLYIMIDE FILMS VIA IN-SITU REDUCTION OF MATRIX CONSTRAINED SILVER(I)

Optically reflective composite polyimide films have been prepared by c asting a dimethylacetamide solution of silver(I) acetate, hexafluoroac etylacetone, and the poly(amic acid) derived from 3,3',4,4'-benzopheno ne tetracarboxylic acid dianhydride (BTDA) and 4,4'-oxydianiline (4,4' -ODA) onto an fully imidized parent BTDA/4,4'-ODA base. Thermal curing of the silver(I)-containing poly(amic acid) topcoat leads to imidizat ion with concomitant silver(I) reduction followed by silver(0) migrati on/aggregation yielding a reflective; but not conductive, silver surfa ce. This ''film-on-film'' composite approach minimizes the silver requ ired for the formation of a reflective surface and preserves the essen tial mechanical and thermal properties of the parent polymer. The meta llized films exhibit outstanding metal-polymer and polymer-polymer adh esion, with the strong metal-polymer adhesion attributable to mechanic al interlocking and/or encapsulation. Films were characterized by X-ra y, DSC, TGA, XPS, TEM, and AFM.