Studying how changes in the structure caused by hydrogen bonding affect the corrosion resistance of polybenzoxazine-based coatings using molecular dynamics simulations

Abstract

Polybenzoxazine (PBz) based coatings were prepared using designed PBz monomers for corrosion protection. The structure and properties of poly(MPM) and poly(POPM) coatings deriving from PBz monomer with methyl group and phenoxy group, respectively, were fully investigated by Fourier transform infrared spectroscopy, water contact angle measurements and electrochemical impedance spectroscopy. For the two crosslinking coating systems, the poly(POPM) coating, with a lower intermolecular hydrogen bonding ratio of 9.7 %, exhibited better hydrophobicity, stability, and corrosion resistance. This is evidenced by a water contact angle (WCA) exceeding 94° (90° for poly(MPM) system) and a charge-transfer resistance surpassing 1 GΩ cm2 (1 MΩ cm2 for poly(MPM) system) even after 30 days of immersion in a 3.5 wt% NaCl solution. The distinct performance in corrosion resistance performance between the two systems can be attributed to structural changes arising from hydrogen bonding, which were extensively investigated through solubility parameters calculation and molecular dynamics simulations in this study. The results show that the prevalence of intra‑hydrogen bonding in the poly(POPM) coating lead to a more compact structure and enhanced hydrophobicity against water, thereby enhancing the barrier ability of PBz based coatings against the penetration of corrosive substances.