Polyanilines, synthesis dopant acid

The second important aspect of polyaniline synthesis is the acid dissociation constant (pA a) of the acid, because in polyaniline protonation equilibria involves exclusively the quinone diamine segment, having two-imine nitrogen with pATai = 1 -05 and pK 2 — 2.55 [20]. Therefore any acid whose value falls within that range would be suitable as a dopant (Table 12.2) whereas the anilinium ion has a pK of 4.60 and the ammonium ion 9.24. 

Campos, T. L. A., Kersting, D. R, Ferreira, C. A. Chemical synthesis of polyaniline using sulphanilic acid as dopant agent into the reactional medium. Surface and Coatings Technology (1999), 122, 3. 

The emeraldine salt of polyaniline which is one of the three different forms of polyaniline—leucoemeraldine (the fully reduced state], emeraldine (the half oxidized state] and pernigraniline (the fully oxidized state] (Fig. 8.1]—is electrically conductive while the others are insulators. Conventional chemical synthesis of polyaniline is based on an oxidative polymerization of aniline by using an oxidant in the presence of a strong acid dopant in the reaction mediunL ... 

The poly aniline nanospheres (PANI-NS) were synthesized by oxidative polymerization of aniline monomer at 0 °C in an ice bath using ammonium persulfate as the oxidant in the presence of surfactant. Aniline, ammonium persulfate, Polyvinylpyrrolidone, cetyl ammonium bromide, and camphorsulfonic acid are used as received from Sigma-Aldrich. Camphorsulfonic acid surfactant as the dopant and ammonium persulfate as the oxidant were used in the present synthesis of polyaniline nanospheres (see flow chart in Fig. 8.11). Calculated quantities of aniline monomer (0.005 mol) were mixed with 50 mL of distilled water and stirred using magnetic stirrer for 10 min. Meanwhile, calculated quantities of surfactant (0.75 mol) and oxidant (0.005 mol) were dissolved separately in distilled water and stirred for 10 min in an ice bath. The surfactant solution was first added to the aniline monomer aqueous solution, and then the previously cooled oxidant solution was added drop wise after which the mixture was allowed to react for 10 h in an ice bath. The precipitate was filtered and washed several times with distilled water and... 

As with the chemically grown nanofibers, the polyaniline nanofibers (PANI-NF-ES) were grown by oxidative polymerization of aniline monomer at 0 °C in an ice bath using ammonium persulfate as the oxidant in the presence of surfactant, though with slightly different conditions. Aniline, ammonium persulfate, dodecyl benzene sulfonic acid, acrylmethylpropyl sulfonic acid, and camphorsulfonic acid are used as received from Sigma-Aldrich. Sulfonic acid-based surfactants as the dopant and ammonium persulfate as the oxidant were used in the present synthesis of polyaniline nanofibers. 

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