Stability Of Polyaniline Research Articles

Investigations on the effect of 5-sulfosalicylic acid on the properties of polyaniline

Results of the investigation of the chemical and electrochemical polymerization of aniline in 5-sulfosalicylic acid medium and its characterization by electrochemical and spectroscopic techniques are presented. The investigation reveals that 5-sulfosalicylic acid as a dopant not only enhances electrochemical stability of polyaniline at higher potentials but also yields a polymer which is soluble to the extent of 11 g/l in DMSO. The characterization of conducting polyaniline thus obtained was carried out by electronic and vibrational spectra, 1H NMR in DMSO-d 6, X-ray powder diffraction, thermal analysis and by electrochemical techniques.

Enhanced electrochromic stability of polyaniline in polyaniline‐matrix polymer composite films in aprotic medium

AbstractElectrochromic behavior and stability in aprotic medium of polyaniline composite films prepared by chemical oxidative polymerization at gas/liquid interface were investigated. The results are compared with chemically and electrochemically snythesized polyaniline homogeneous films. The polyaniline composite films show almost the same electrochromic behavior as the homogeneous films. The behavior is due to a two‐step oxidation mechanism, which is different from that in aqueous medium, especially in the second oxidation process. Degradation of polyaniline in aprotic medium is due to the partial formation of the electrochemically inactive quinonediimine structure in the higher oxidized state. The degradation is restrained by hybridization with an appropriate matrix polymer. The stabilization of the electrochromic behavior of polyaniline depends on molecular weight and pKa of the matrix polymer.

Thermal stability of polyaniline

Thermal stability data for neutral (emeraldine base) and doped polyaniline with various counter anions are reported. The emeraldine base is a highly heat-stable polymer, with thermal stability up to 420 °C. The thermal stability of doped polyaniline is dependent on the counter anion. The methane sulfonic acid doped polyaniline is stable up to 250 °C. The decomposition of the doped polyaniline is seen as a two-step process. The first step is the loss of the dopant and the second step corresponds to the decomposition of the backbone.

Thermal stability of polyaniline

The thermal stability of conductive polyaniline prepared by the chemical oxidation of aniline with ammonium persulfate in hydrochloric acid was investigated by a heat-aging test at 150 °C. The stability in terms of electrical conductivity was found to depend upon the sample form as well as on the environment. The extent of deterioration in electrical conductivity decreased in the order of the powder in air, the disk in air and the powder in vacuo. From the elemental analysis, infrared and Raman spectroscopies, X-ray photoelectron spectroscopy and electron probe micro-analysis, the deterioration in the presence of air was assumed to be based on the chemical change involving the elimination of hydrochloric acid on the amino group and the simultaneous chlorination of the aromatic ring.