New poly(p-substituted-N-phenylpyrrole)s. Electrosynthesis, electrochemical properties and characterization

Poly(N-p-hydroxyphenylpyrrole) [poly(HOPhPy)], poly(N-p-methoxyphenylpyrrole) [poly(MeOPhPy)], poly(N-p-thiophene-phenylpyrrole) [poly(ThPhPy)], poly(1,1′-phenylene dipyrridyl) [poly(PhDPy)] and poly(1,1′-diphenylene dipyrridyl) [poly(DPhDPy)] were electrosynthesized from the corresponding monomers on Pt electrode in 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) acetonitrile solutions, using cyclic voltammetry (CV), galvanostatic and potentiostatic modes. The electrodeposited films were characterized by CV, FT-IR spectrometry, X-ray photoelectron spectra (XPS), and scanning electron microscopy (SEM). Electron-donating substituent effects on the polymer electrochemical properties were investigated by CV. The CV of the films indicated a good redox behaviour and a peak position depending on the nature of substituent. FT-IR spectral studies allowed one to predict a linear and regular structure of the polymer chains, the coupling taking place in the 2 and 5 positions of the pyrrole rings. XPS analysis showed a variation of the film doping levels (26–42% for oxidized films and 6–12% for reduced films) with the electron-donor character of the phenyl p-substituents. The conjugated π-electronic system was extended by strong electron-donating substituents which led to a higher doping level of the polypyrrolic chains and a polymer structure with high-energy and polar bonds like CN+ and CN+. SEM analysis revealed changes in the polymer film morphology and thickness with the nature of substituents.