Abstract:
Polyanilines are prepared by electrochemical oxidative polymerzation of
aniline at different bath composition, temperature and current density/The
different bath compositions used were:
/ monomer
(aniline)
20 mIll
acids:
(H2S04! HCI! HCI04)
100 mill
Electrochemical depositions were carried out at 5°C, 9°C, 18°C and 25°C on
Pt-electrode. The deposition current densities were 5 mA/cm2
, 10 mA!cm2
and 15 mA!cm2 Optimal conditions for the electrosynthesis of polyaniline
were also determined. The polymers obtained in this study under different
conditions were characterized by IR, X-RD and elemental analysis. The d.c.
conductivity and UV-Vis spectroscopy measurements were performed to
have an insight in the electrical and optical properties of the studied
polyaniline. To determine the nature of conductive polymer, electrical
conductivities of the polymer samples were measured at different
temperatures. Most of the samples except one (prepared in H2S04 solution)
showed their semiconductive behavior i.e. their electrical conductivity
increases with the increase of temperature. The only sample prepared in
presence of H2S04 showed metallic behavior. Its electrical conductivity
decreases with the increase of temperature which is quite peculiar. The
resistance of this sample is much lower than those of other samples. In the
IR spectra, the band characteristics of aniline confirmed the presence of
monomer ring in the polymer.
X-ray diffraction patterns of polyaniline showed two peaks at 28 valued
around 9° and 12°. The peaks were found diffuse. Relatively better
crystallinity was observed in the case of smaller molecular size dopant. The
experimental results of elemental analysis were found slightly lower than
those of the corresponding theoretical values. UV visible spectra of
polyaniline showed the two absorption bands. Bands at around 335nm are
due to rc-+ rc* transition. The broader bands at around 500-540nm might be
due to n-+ rc* transition. Relatively lower temperature, lO mA/cm2 current
density and H2S04 electrolyte are found suitable for the synthesis of better
quality of conductive polyaniline.
