Controlling Segregation States and Chemical Interactions to Modulate the Water-Triggered Release of Organic Corrosion Inhibitors from Polymer Films

This work presents a strategy to control the dispersion and stratification degree of functional organic molecules, such as organic corrosion inhibitors, in polymeric matrices and studies its effect on their water-controlled release. 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) was used as the model inhibitor and p (BMA-co-MMA) as the polymer matrix. By systematically varying solvent–inhibitor compatibility and inhibitor loading, films with distinct and previously unreported self-stratified architectures were obtained, exhibiting different degrees of inhibitor dispersion and aggregation. Poor DMTD solubility, as in toluene, produced stratified films, whereas better solvents such as tetrahydrofuran, methyl ethyl ketone, and methyl isobutyl ketone yielded dispersions governed by solubility and evaporation rate. Uniform dispersion, typically accompanied by larger Tg depression, generally correlated with faster initial release in salty water, though this effect could be offset by stronger inhibitor–matrix interactions. Aggregate- or layer-rich structures supported extended inhibitor release through gradual inhibitor dissolution in the DMTD-rich domains in the hydrophobic polymer matrix. Preliminary immersion tests on AA2024 demonstrate that DMTD released from the coatings remains corrosion-active, effectively suppressing localized corrosion following coating damage. Overall, the ability to tailor film structure through solvent selection and inhibitor concentration represents a powerful tool for embedding reactive molecules in polymer matrices for use in engineering coatings.