Metallized polyimide films: Metallization and mechanism of the process

The formation of metallized polyimide films in situ, namely, the alkaline hydrolysis of film surfaces, chelation of the modified surface with metal ions, and their chemical reduction giving rise to a metal layer, has been investigated. Initial polyimide films are cast from reaction solutions on a glass substrate. The solutions are prepared through the polycondensation of dianhydride of tricyclo4.2.2.0^2.5dec-7-ene-3,4,9,10-tetracarboxylic acid and 4,4¹-diaminodiphenyl oxide in N-methyl-2-pyrrolidone at 160°C. It has been shown that alkaline water-alcohol solutions are optimal media for the hydrolysis of the film surface. The maximal exchange of alkali metal ions is achieved through formation of a more stable metal-ligand complex of poly(amido acid), with the chelation rate depending on the nature of a metal. The metal reduction proceeds rapidly; however, the mechanism of this process depends on the pH of a medium. The annealing of metallized films results in the imidization of poly(amido acid) and in the growth of metal grains on the material surface to yield a metal layer with good optical properties and high conductivity.