Acid Doping of Polyaniline:  Spectroscopic and Electrochemical Studies

Abstract

A detailed investigation of the acid doping behavior of polyaniline has led to a robust and reproducible procedure for controlled adjustment of the redox state of dry polyaniline films. The initial step in this procedure is the casting of PANI films from formic acid. The subsequent exchange of the trapped formic acid for other primary dopants obtained from mono-and polyprotic acids (e.g., CH 3 COO -, BF 4 -, HSO 4 -, SO 4 2-, H 2 PO 4 -, and HPO 4 2-) is demonstrated. The voltammetric and the spectroscopic behavior of the PANI doped with different anions indicate that both the protons and the anions of dopant acids influence the structure and redox properties of the polymer. The redox state of PANI doped with homologous series of chloroacetic and carboxylic acids correlates with the pK a of the dopant acid. These results show that it is possible to prepare the polymer with a desired oxidation state according to the pK a of the dopant acid of a given homologous series. The exchange of the formic acid for both stronger and weaker doping acid can be repeatedly accomplished by electrochemical cycling.

Polyaniline-Doped Spherical Polyelectrolyte Brush Nanocomposites with Enhanced Electrical Conductivity, Thermal Stability, and Solubility Property

“…two characteristic absorption peaks of a quinone ring and a benzene ring have shifted to the low wavenumber by doping, which may be due to the enhancement of delocalization of charge electron by chemical oxidative polymerization doping [25]. However, the extent of shift is slightly different.…”

Nanostructured Polyaniline Emeraldine-base form (EB-PANI): a structural investigation for different neutralization times

“…[37] A strong characteristic band appears at $1160 cm À1 , which has been explained as an electronic band [38] or a vibrational band of nitrogen quinine [37]. The CAH out-of-plane bending mode has been used to identify the type of substituted benzene [39]. For EB-PANI this mode was observed as a single band at 825 cm À1 , which is found in the range of 800-860 cm À1 predicted for a 1,4-substituted benzene.…”

“…Thus, the FTIR spectrum is evidence of the formation of EB-PANI with very low degrees of branching and/or crosslinking. The 1132 cm À1 band in ES-PANI is a vibrational mode of BANH + @Q or BANH + AB, which is formed in doping reactions [37,39]. This band is very intense and broad.…”

Nanocomposite based on polyaniline emeraldine-base and α-Al2O3: A structural characterization

“…The bands at 1140 cm -1 can be attributed to the inplane C-Hbending modes. The C-Hout-of-plane bending mode has been used as ak ey to identify the type of substituted benzene [35]. For PANI-EB, this mode is observed as asingle band at 822 cm -1 ,which falls in the range of 800 -860 cm -1 predicted for a1 ,4-substituted benzene.…”