Synthesis and electrochemical properties of electroactive aniline-dimer-based benzoxazines for advanced corrosion-resistant coatings
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The first high-performance electroactive benzoxazine with an aniline dimer in its structure has been synthesized from 4-aminodiphenylamine (aniline dimer), paraformaldehyde, and phenol. FT-IR and 1H NMR are used to characterize the molecular structure of the electroactive benzoxazine monomer (PH-BA). The reversible one-electron transfer between the neutral form and the radical-cation form takes place in the redox reaction of PH-BA and its corresponding polymer (pPH-BA). The pPH-BA exhibits oxidation and reduction currents of 0.122 and 0.128 mA cm−2, respectively, which are higher than the published benzoxazine/aniline oliogomer blend. The current value of the redox peaks of pPH-BA doubles when compared with PH-BA, which might be attributed to the formation of the electron-donating hydroxyl groups during the thermally induced ring-opening polymerization and the hydrogen bonding interactions between phenolic-OH groups and aniline units in pPH-BA network. The pPH-BA coating exhibits outstanding corrosion resistance properties with a corrosion rate of 0.0091 mm per year for carbon steel Q235, which is significantly lower than that of non-electroactive polybenzoxazines. pPH-BA can further facilitate the formation of a metal oxide layer composed of Fe2O3 on the steel surface and was characterized by SEM, Raman, and XPS.
This work was financially supported by the National Natural Science Foundation (51373141) and (51703191) of China and the Scientific Research Innovation Team of University in Sichuan Provence (16TD0009), and the Open Experiment Project of Southwest Petroleum University (KSZ17120), P.R. China.
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There are no conflicts to declare.
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