Some Specific Features in the Applying the Method of Raman Spectroelectrochemistry while Studying Polyaniline Electrosynthesis in Polymeric-Acid Medium

Аннотация

Initial stages of aniline galvanostatic polymerization at platinum electrode in aqueous solutions of poly-2-acrylamido-2-methyl-1-propansulfonic acid and polystyrenesulfonic acid are studied by the method of Raman spectroelectrochemistry. A laser with wavelength of 532 nm excited the Raman scattering. The very presence of intermolecular associates able to luminescence in the polyacid solution (in the case of polystyrenesulfonic acid) was shown to result in the Raman-spectrometer photodetector overload if normal incidence of laser beam at the electrode (the angle 0°) was used. The Raman-spectrometer photodetector overload can be avoided by the varying of the incidence angle over the 0°–20° range, even without using other techniques (leading to a decrease in the reliability of the studied Raman band registration, such as the lowering of the integration time, intensity or energy of the excitation). Comparative study of aniline electropolymerization in the presence of poly-2-acrylamido-2-methyl-1-propansulfonic acid, polystyrenesulfonic acid, and HCl revealed some characteristic bands in the Raman spectra of the polyaniline–polyacid complexes in the Raman frequency range from 2000 to 3000 сm^–1; these bands relate to the polyacid’s backbone and are absent in the Raman spectra of the polyaniline–HCl film. The dynamics of changes in the contribution to the integral Raman spectrum of the band of radical-cations (1330–1350 сm^–1) characterizing the highly conductive emeraldine form of polyaniline was compared for the polymerization media. In the course of the electrosynthesis it was found, that the accumulation rate of these species in the film decreased in the series poly-2-acrylamido-2-methyl-1-propansulfonic acid > HCl > polystyrenesulfonic acid.