Polyaniline doping/dedoping process

Polyaniline can undergo a reversible acid/base doping/dedoping process. In the emeraldine salt form, polyaniline is conductive. This form can then be converted to the insulating emeraldine base form of polyaniline, upon exposure to base as in Equation 1, where HX is a protonic acid ... 

Infrared spectroscopy is a powerful tool to determine the structural changes that occur during doping (dedoping process). Various groups have reported FTIR results of polyaniline [167-78]. It has been shown that the absorption frequencies are strongly influenced by the electrochemical potential (Table 12.15). 

It has been reported that densificadon of polyaniline can occur when doped with protonic acids (11). The densities of as-cast, fully doped and redoped polyanilines were reported to be 1.3, 1.4 and 1.32 g/cm respectively (11). The densification causes a reduction in the free volume, through which gas molecules can permeate. Therefore, it is also possible that the doping or dedoping process results in a free volume change which dictates the gas permeability. 

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