SYNTHESIS OF SURFACE-METALLIZED POLYIMIDE FILMS VIA IN-SITU REDUCTIONOF (PERFLUOROALKANOATO)SILVER(I) COMPLEXES IN A POLY(AMIC ACID) PRECURSOR

Thermal curing of the silver(I)-containing poly(amic acid) formed from 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) and 4, 4'-oxydianiline (4,4'-ODA) in dimethylacetamide leads both to polyimid e films via cyclodehydration and to reduction of silver(I) giving a me tallized surface. The resulting metallized composite films retain mech anical and thermal properties similar to those of the parent polyimide . Variation of the silver(I) additive and concentration and the therma l cure cycle allows the fabrication of silver layers which are both re flective and/or electrically conductive. Silver(I) trifluoroacetate an d pentafluoropropanoate give excellent silvered films; however, higher perfluoroalkanoates such as silver(I) heptafluorobutanoate give films which are poorly surface metallized and extensively bubbled. X-ray di ffraction shows crystalline face-centered cubic silver in the films af ter thermal curing. Microscopy data show that the surface particle siz es are in the range of ca. 100-500 nm. Significant silver remains in t he bulk of the polyimide film with varying particle sizes generally le ss than ca. 15 nm. The interior of the metallized films is not electri cally conducting. Films were characterized by X-ray diffraction, diffe rential scanning calorimetry, thermogravimetric analysis, X-ray photoe lectron spectroscopy, transmission electron microscopy, scanning elect ron microscopy, and atomic force microscopy.