Polyaniline nucleophilic substitution reaction

Apart from chemical synthesis, electrochemical synthesis is a versatile method for the preparation of self-doped sulfonated polyaniline in both soluble forms and thin films deposited on an electrode surface. Electropolymerization of sulfonated polyaniline homopolymers and copolymers has been carried out in aqueous and nonaqueous media. Similar to chemical synthesis, electrochemically controlled electrophilic and nucleophilic substitution reactions are also reported. 

In addition to sulfonic acid groups, carboxylic acid groups as ring substituents results in self-doping of polyaniline and influence properties such as solubility, pH dependent redox activity, conductivity, thermal stability, etc. Sulfonated polyanilines are typically obtained by postpolymerization modifications such as electrophilic and nucleophilic substitution reactions. However, carboxylic-acid-functionalized polyanilines are typically synthesized directly by chemical and electrochemical polymerization of monomer in the form of homopolymer or copolymer with aniline. In contrast to sulfonated polyaniline, very few monomers are available for the synthesis of carboxyl acid functionalized polyaniline. Anthranilic acid (2-aminobenzoic acid) is an important monomer and is often used for the synthesis of carboxyl acid functionalized polyanilines. 

G. Liu, M. S. Freund, Nucleophilic substitution reactions of polyaniline with substituted benzenediazonium ions a facile method for controlling the surface chemistry of conducting polymers, Chemistry of Materials 1996, 8, 1164. 

An alternative route to modify polyaniline involves nucleophilic substitution. In 1989, Genies et al. [58] synthesized self-doped polyaniline using the reaction of the emeraldine base with propanesultone as well as butanesultone. The proposed mechanism involves nucleophilic attack... 

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. 

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