Synthesis and characterization of some novel polythiophene derivatives containing pyrazoline

Eight polythiophene derivatives containing pyrazoline side groups were synthesized by a chemical oxidative coupling polymerization using FeCl₃. The crystal structures of four monomers were determined which confirm the almost perpendicular orientation of the thiophene and pyrazoline rings, while the other substituents are more coplanar. Analyses of IR, ¹H-NMR, Raman and UV-Vis spectra demonstrated that the suggested polymerization was successful to generate the synthesized polythiophenes with the expected structures. The morphology of the synthesized polythiophenes was studied by SEM. The different substituents attached to the 1- and 3-positions of the pyrazoline side chain led to differences in optical properties, electrical conductivity, and thermal stability of the synthesized polythiophenes. By adding a pyrazoline side chain to polythiophenes, some polymers achieve good solubility, electrical conductivity of about 1.3 × 10^–6 S/cm, high fluorescence intensity (above 40,000 a.u.) at 505–550 nm and thermal stability up to 590°C in the air.

Synthesis and Characterization of Polypyrrole Film Doped with Both Molybdate and Salicylate and Its Application in the Corrosion Protection for Low Carbon Steel

Polypyrrole (PPy) films doped with molybdate and salicylate have been successfully electropolymerized on low carbon steel in aqueous solutions containing both molybdate and salicylate in a one-step process that did not require any pre-treatment of the steel substrate. Salicylate-doped PPy films were synthesized in the same way for comparison. The steel surface was rapidly inhibited and the PPy-based films were formed on it easily. The PPy-based films were characterized by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray, and thermal gravimetric analysis methods. The corrosion protection performance of the coatings was investigated with electrochemical impedance spectroscopy, open circuit potential (OCP), salt spray test, and Tafel polarization. It was found that in the presence of both molybdate and salicylate as dopants, the films on steel could present a better corrosion resistance than PPy film doped with only salicylate. The self-healing property of PPy-based films was observed on the OCP measurement with the fluctuation of rest potential. The salt spray test results showed that the PPy film doped with both salicylate and molybdate was more salt-resistant than the PPy film doped with only salicylate. The results suggest that the PPy coatings doped with both molybdate and salicylate are potential for application as metallic anti-corrosion coatings.