Emeraldine base electrochemically prepared films

Han et al. [64, 66] reported the synthesis of highly conductive and thermally stable self-doped mercaptopropanesulfonic-acid-substituted polyanilines by the concurrent reduction and substitution reaction between polyaniline and a nucleophile. These reactions were carried out on both electrochemically generated and free standing polyaniline films prepared from emeraldine base dissolved in N-methylpyrrolidinone. The electrochemically prepared films were dedoped with 5 % aqueous NaiCOs to convert them the into the emeraldine base form. The sulfonated polyaniline was prepared by reaction of a polyaniline emeraldine base film with 0.1 M 3-mercapto-l-propanesulfonic acid sodium salt in methanol under nitrogen at room temperature for approximately 14h [66]. A catalytic amount (0.01 M) of acetic acid was reported to accelerate the reaction. The resulting sulfonated polyaniline film was thoroughly rinsed with methanol, followed by 5 % aqueous NaiCOs to remove reactants. 

PANI is commonly prepared by chemical polymerization of aniline using (NH4)2S20s in hydrogen chloride solution (187) and/or by electrochemical polymerization (188). PANI can exist in four different oxidation states leucoemeral-dine (neutral form), pernigraniline (quinoid-like form), emeraldine base (intermediate form), and emeraldine salt (conductive form), as shown in Figure 7. PANI is prepared as the emeraldine salt and then treated with base to yield the emeraldine base form, which is soluble in common organic solvents. After film casting or... 

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