Reflective and conductive surface-silvered polyimide films prepared by surface graft copolymerization and electroless plating

Argon plasma-pretreated polyimide (PI) films were subjected to UV-induced surface graft copolymerization with 4-vinylpyridine(4VP) under atmospheric conditions. Electroless plating of silver was carried out effectively on the 4VP graft copolymerized PI (PI-g-P4VP) surface after PdCl₂ activation and in the absence of SnCl₂ sensitization (the Sn-free process). The surface compositions of the modified PI films were studied by X-ray photoelectron spectroscopy (XPS). XPS results showed that the PI-g-P4VP surface is ready for electroless deposition of silver via the Sn-free process. The grafted 4VP layer with well-preserved pyridine groups was used not only as the chemisorption sites for the palladium complexes (without the need for prior sensitization by SnCl₂) during the electroless plating of silver, but also as an adhesion promotion layer for the electrolessly deposited silver. The silver metallized PI films show high reflectivity and conductivity with a surface resistance of Ω 1.5 and a reflectivity of 91.3%, respectively.