Concurrent N-alkylation and doping of polyaniline by alkyl halides

The N-alkylation of polyaniline (PANi) was investigated by treating the fully reduced state (leucoemeraldine or LM) and the 50% oxidized state (emeraldine or EM) directly with various alkyl halides. The degree of alkylation of LM is low (<10%), while that of EM base is much higher (can be >30%), suggesting that the imine nitrogen is more reactive as a nucleophile than the amine nitrogen in the alkylation reaction. Evidence of concurrent doping of PANi during the N-alkylation process was obtained using UV-visible absorption spectroscopy, FTIR spectroscopy, XPS, and conductivity measurement. The electrical conductivity of the N-alkylated PANi is strongly dependent on the degree of alkylation. The effects of the various alkyl halides, solvents, and reaction temperatures on the degree of alkylation and reaction rate were studied. The mechanism of the N-alkylation reaction and the structure of the resulting product were postulated.