Substitution, polyaniline synthesis

Sharma, A.L., M. Gerard, R. Singhal, B.D. Malhotra, and S. Annapoorni. 2001. Synthesis and characterization of fiuoro-substituted polyaniline. Appl Biochem Biotechnol 96 (1-3) 155-165. 

A. Gok, B. Sari, M. Talu, Synthesis and characterization of conducting substituted polyanilines, Synthetic Metals 2004,142, 41. 

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. 

F. Cataldo, P. Maltese, Synthesis of alkyl and n-alkyl-substituted polyanilines - a study on their spectral properties and thermal stability, European Polymer Journal 2002, 38,1791. 

Synthesis and electrochemistry of alkyl ring-substituted polyanilines. J. Phys. Chem., 93, 495-499. 

Leclerc [125] has shown that poly(2-methyl aniline) has properties similar to that of polyaniline. Dao et al. [127] have carried out extensive investigations on chemical and electrochemical polymerization of substituted polyanilines. These authors report that chemical synthesis yields a polymer having a higher molecular weight. Some of their results are given in Table 12.13. Their study further shows that there is no polymer film on an electrode surface in the presence of the following substitutions ... 

Electroactive polyaniline films were synthesized by the catalysis of biUru-bin oxidase (BOD, a copper-containing oxidoreductase). The polymerization of aniline was carried out on the surface of a sohd matrix such as glass sUde, plastic plate, or platinum electrode to form homogeneous films [33]. The BOD was immobilized on the surface by physical absorption. The optimum pH was around 5.5. Some aniline derivatives such as p-aminophenol and p-phenylenediamine were good substrates for BOD. Structural analysis suggested the BOD synthesized polyanihne possessed partially 1,2-substititued structures. Cyclic voltammetric studies demonstrated that the PANl films were electrochemically reversible in redox properties, but differed from that of chemically or electrochemically synthesized PANl. The difference was attributed to the partial 1,2-substitution. Laccases are known to oxidize phenolic compounds in nature in the presence of oxygen and are capable in polyaniline synthesis in vitro [34-36]. 

Yavuz, A. G., Uygun,A.,Bhethanabotla, V. R. Substituted polyaniline/chitosan composites Synthesis and characterization. Carbohydrate Polymers (2009), 75,448-453. 

Yavuz, A. G., Uygun, A., Can, H. K. The effect of synthesis media on the properties of substituted polyaniline/chitosan composites. Carbohydrate Research (2011), 346, 2063-2069. 

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. 

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