Chemical structure and molecular arrangement in electrodeposited polypyrrole layers doped with dodecyl sulfate anions: NEXAFS and XPS analysis
- Dr. Alena MARATKANOVA
- Dr. Alena MARATKANOVA (Udmurt Federal Research Center, Ural Branch of Russian Academy of Sciences, Izhevsk, Russia)
- Dr. Alexander SYUGAEV (Udmurt Federal Research Center, Ural Branch of Russian Academy of Sciences 132 Kirov Street, Izhevsk, Russia)
- Dr. Natalia LYALINA (Udmurt Federal Research Center, Ural Branch of Russian Academy of Sciences 132 Kirov Street, Izhevsk, Russia)
- Dr. Anatoly SHAKOV (Udmurt Federal Research Center, Ural Branch of Russian Academy of Sciences 132 Kirov Street, Izhevsk, Russia)
- Dr. Dmitry SMIRNOV (Institut für Festkörperphysik, Technische Universität Dresden, Physikgebäude, Zellescher Weg 16, 01069, Dresden, Germany)
Electrodeposited films of polypyrrole are widely used in many technological applications, including anticorrosive protection of metal and steels . It is known that the protective effect of coatings can be significantly improved by doping the polymer with alkyl sulfates or alkyl sulfonates, for example, dodecyl sulfate anions . In this work, polypyrrole films were grown by electropolymerization of pyrrole from aqueous solutions in the presence of dodecyl sulfate additives. For the first time, the chemical structure and spatial arrangement of the molecules in the as-grown polymer films were studied by means of XPS and angular-dependent NEXAFS spectroscopy. The spectra were measured at the Russian-German beamline at BESSY II (HZB, Berlin).
It has been found that the films are characterized by one dodecyl sulfate anion for each nitrogen atom. One-fourth of all the nitrogen atoms are in radical cations, with the rest atoms being in the protonated amino groups. This structural feature leads to almost complete disappearance of π* resonances in the nitrogen K edge NEXAFS spectra. The films grow through 2D growth mechanism and comprise of thin plates preferentially oriented in-plane substrate surface. Linear dichroism of the NEXAFS spectra was observed for these films. The changes observed in the spectra indicate the presence of 2D-polypyrrole sublayers with pyrrole rings lying in-plane the substrate and sub-layers of surfactant anions with their tails oriented upright the substrate. High anticorrosive properties of the doped polypyrrole films may arise from the revealed structural and molecular arrangement features.
This work was supported by Russian Foundation for Basic Research (No.16-43-180228), bilateral Program "Russian-German Laboratory at BESSY II" and partially by FASO of Russia within the state assignment No. АААА-А17-117022250038-7.
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