Kenji Akami

Solid electrolytic capacitor with highly stable conducting polymer as a counter electrode

We developed a new type of tantalum solid electrolytic capacitor using poly(3,4-ethylenedioxythiophene) (PEDOT) as a counter electrode. The polymer counter electrode was formed on a sintered and anodized tantalum substrate by chemical polymerization. The capacitor was characterized by excellent frequency characteristics and superior durability, due to which it functioned without any deterioration for more than 1000 h at 125°C in air and at 85°C/85%RH.

Chemical polymerization of 3,4-ethylenedioxythiophene using an aqueous medium containing an anionic surfactant

Abstract We found that a good yield of poly(3,4-ethylenedioxythiophene) (PEDOT) was obtained by emulsion polymerization in which an anionic surfactant and Fe 2 (SO 4 ) 3 were used as an emulsifier and an oxidant, respectively. The major feature of this polymerization is that highly conductive PEDOT is formed in an aqueous medium containing such a low concentration of 3,4-ethylenedioxythiophene (EDOT) and Fe 2 (SO 4 ) 3 as 0.05 M. This is most likely due to the polymerization progressing in the innumerable micelles where hydrophobic EDOT is concentrated. The thermal stability of PEDOT obtained here is superior to that of polypyrrole prepared in a similar manner, although its moisture stability is inferior.

Properties of chemically prepared polypyrrole with an aqueous solution containing Fe2(SO4)3, a sulfonic surfactant and a phenol derivative

Abstract This paper describes chemically prepared polypyrrole (PPy) with an aqueous solution containing Fe 2 (SO 4 ) 3 as an oxidant. PPy having enhanced conductivity and environmental stability was obtained under the coexistence of a sulfonic surfactant and a phenol derivative with an electron-withdrawing group. The effect of the sulfonic surfactant was ascribed to a large-sized sulfonic anion being selectively incorporated into PPy as dopant, because an increase in the yield of PPy depended on the concentration of the surfactant. For PPy synthesized with a solution containing p -nitrophenol (pNPh), a clear increase in the doping ratio was recognized from elemental analysis. Moreover, the conductivity of PPy increased with increasing strength of the electron-withdrawing force of the substituent. The electron-withdrawing substituent of the phenol derivative seems to prevent undesirable side reactions so as to improve the regularity of the PPy backbone.

Chemical polymerization of 3,4-ethylenedioxythiophene in an aqueous medium containing a phenol derivative as an additive

Abstract In this paper, we describe poly(3,4-ethylenedioxythiophene) (PEDOT) prepared in an aqueous medium containing Fe 2 (SO 4 ) 3 and alkylnaphthalenesulfonate as an oxidant and a dopant, respectively. It is found that the addition of p -nitrophenol leads to an improvement of the moisture stability of PEDOT as well as an increase in yield. On the other hand, the initial conductivity of PEDOT decreased slightly. An increase in yield and a decrease in conductivity were also observed when other phenol derivatives with a strong electron-withdrawing substitute, such as m -nitrophenol and p -cyanophenol, were added. The effects of phenol additives on PEDOT were different from those on polypyrrole, in which an increase in conductivity and a slight decrease in yield were observed.