Preparation of Silvered Polyimide Mirrors via Self-Metallizing Poly(Amic Acid) Resins

Abstract

The use of metallized reflectors with polymeric rather than glass substrates for solar energy concentration can reduce greatly the weight and fragility of such mirrors and provide greater flexibility of packaging for subsequent deployment in space applications.¹ Silver is the metal of choice for the reflecting material. The specular reflectance of silvered mirrors is excellent, and the hemispherical reflectance of a clean silver film is greater than 97% weighted over 250-2500 nm, the range of the solar spectrum.² Most commonly, metallized polymeric films are fabricated in two steps. First, the polymeric film is prepared, and secondly, the metal is deposited onto the film surface by an external process such as thermal or chemical vapor deposition, sputtering, or chemical reduction from solution. Often, adhesion of the more passive metals such as copper, silver, and gold to the polymer is a problem.^3,4 In this work we report the preparation of silvered polymeric films via an especially convenient and effective single-step in situ self-metallization procedure involving reduction of polymer-soluble silver(I) to the metallic state. The formation of silvered mirrors, as will be described, has the potential to give improved adhesion as well as highly reflecting surfaces.