Doping dedoping process

ZB Zhang, M Fujiki, M Motonaga, and CE McKenna, Control of chiral ordering in aggregated poly 3-(S)-[2-methylbutyl]thiophene by a doping-dedoping process, J. Am. Chem. Soc., 125 7878-7881, 2003. 

PPy film is blue-violet in doped (oxidized) stet. Electrochemical reduction yields the yellow-green undoped form. The schematic of the doping/dedoping process can be given as... 

The doping of the conducting polymer is generally obtained during the electropolymerization of the monomer, with perchlorate or sulphate anions for examples. The doping-dedoping process is essential for the electroactivity of the polymer. Various electro-active anionic species, such as tetrasulphonated metal... 

A solid-state synthesis has been explored to prepare PANI nanostmctures with many convolutions, which resemble the cerebral cortex of the brain (Figure 2.26), via the oxidative polymerization of solid anilinium citrate with chlorine gas [428]. A reversible doping/ dedoping process (i.e., conducting state/insulating state) for the brain-like nanostructures was realized by using HCl gas/ammonia gas. 

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 ... 

Moreover, the combination of SPR and an electrochemical allows for in situ kinetic investigation, a doping-dedoping process, and optical property changes during electropolymerization of electroactive monomers and has also been recently used in immunosensor applications [45, 49-52]... 

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). 

The poly(pyrrole-co-pyrrole-A/-alkylsulfonate)s belong to a class of materials that have been termed self-doping. They possess an anionic dopant ion covalently attached to the polymer backbone, forcing predominant cation movement during the doping/dedoping process. The most highly studied copolymer in this family has been prepared from pyrrole and 3-(pyrrol-l-yl)propane-... 

Because the oxidative potential of polypyrrole and hydrogen are very close, the electrochemical p-doping and dedoping processes can be simultaneously accompanied by the reduction/oxidation of hydrogen in aqueous environments. Which process dominates can depend on many factors such as pH, nature of the electrolyte, additives, and dopants. Also to be considered when the polymer is coupled with a passivating metal are two possible anodic reactions oxidation of the polymer backbone and polarization of the metal surface to produce a metal oxide film. Another possibility is an irreversible anodic overoxidation of the polymer that can occur at potentials more positive than that of the reversible doping-dedoping process. 

The present work attempts to trace chemical changes in the PPy structure on a doping/dedoping process in an aqueous system of an electrolyte by employing Raman and optical spectroscopy. 

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