NEXAFS study of molecular arrangement in polyaniline films prepared by electrochemical deposition
- Dr. Alexander SYUGAEV
- Dr. Alexander SYUGAEV (Physical-Technical Institute UB RAS, Izhevsk, Russia)
Nanoscale films based on conductive polymers and polyaniline/polypyrrole multilayers are of great interest and may be used in various applications such as protective and antielectrostatic coatings, membranes, sensors, capacitors, etc. Physical-chemical properties of polyaniline films depend on their molecular arrangement. Up to date, the effect of the electrochemical synthesis conditions on the chemical structure and molecular orientation in the films is far from being comprehensively studied. In the work, the polarization-dependent NEXAFS spectra were used to obtain the data on the molecular arrangement in a relatively thick (~1 micron and thicker) polyaniline films. The influence of different parameters of electrosynthesis was investigated such as polarization potentials; polarization modes (potentiostatic, cyclic); growth from still/stirring electrolyte solution. XPS and NEXAFS spectra were measured at the dipole Russian-German beamline at the BESSY II, HZB Berlin.
In most films, the polarization-dependent NEXAFS spectra have shown a preferential orientation of the macromolecular chains of polyaniline in the surface layer of the films. The films are arranged differently depending on the preparation conditions. For example, at the initial stages of the deposition under potentiostatic conditions in stirring electrolyte, most of the aromatic rings of the polymer molecules are arranged along with the film surface. With increasing deposition time, a preferential molecular orientation disappears. For the film prepared under the same conditions, but in still electrolyte, there is significant polarization effect, indicating that the aromatic rings are arranged perpendicular to the sample surface. However, the polymer chains themselves are oriented along with the sample surface. Such an orientation of the molecules can be assigned to the capture of macromolecular fragments and oligomers from the near-electrode layer, in which these fragments are accumulated.
The work was supported by the Russian Foundation for Basic Research (grant № 16-43-180228) and the Russian-German Laboratory at BESSY II, HZB Berlin.