Polyaniline, carboxylic acid derivative

Both the imine and the secondary amine nitrogens in polyaniline can be protonated by weak carboxylic acids of different pK values. Solid layers prepared from such doped polyanilines have different selectivity for interaction with gases. It is partially derived from the interaction of the analyte with the doping anion. 

In addition to functionalization of polyanilines with sulfonic and carboxylic acids, the corresponding phosphonic acid derivatives have been prepared, o-Aminobenzylphosphonic acid was prepared as shown in Figure 20.54 [42,43]. Oxidative coupling of the above monomer in an acidic medium yielded poly(o-aminobenzylphosphonic acid) (Figure 20.55). Spectroscopic analysis was consistent with head-to-tail oxidative coupling through the /Jara-position. The as-prepared polymer was in its emeraldine oxidation state in which 43% of the N-atoms were protonated by the pendent acid. This polymer was insoluble in both non-aqueous solvents and aqueous acidic solutions. 

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