Structure and properties of polypyrrole synthesized under air and oxygen-free conditions

We have succeeded in manufacturing a chip-type tantalum capacitor using conducting polypyrrole (PPy) as a solid electrolyte. PPy was fabricated by the direct polymerization of pyrrole on the dielectric layer of the capacitor. Diffuse reflection-absorption FT-IR spectroscopy indicates that the PPy has an oxidized structure with covalently bonded oxygen, which differs from native PPy synthesized under oxygen-free conditions. We investigated the thermostability of oxidized and native PPys in an inert atmosphere. The room temperature conductivity of both PPys remained unchanged despite annealing at up to 260°C. Gas chromatography-mass spectrometry indicated that the elimination of dopants begins at 330°C and the main chain decomposes at 480°C. We observed no difference in the thermostability of oxidized and native PPy. These results prove that PPy in a sealed container can be adapted for use as a material for electronic devices that need to remain stable at high temperatures. A sealed tantalum capacitor made using PPy was able to operate continuously at 125°C.