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The healing of epoxy coatings in damaged areas significantly influences their service life and protection quality. Intrinsic self-healing coatings, which enable multiple healing cycles without the need for additional functional carriers, have emerged as a promising coating technology. Nevertheless, the cross-linked structure of thermoset epoxy coating system restricts the large-scale migration of molecular chains, posing a significant challenge to achieve intrinsic healing of resin without compromising its mechanical properties. In this study, we report a design scheme for epoxy coating with intrinsic self-healing properties based on active multiple hydrogen bonds. Grafting aminobenzothiazole at the end of polyetheramine D230 chain, the grafted polyetheramine (GD230) was synthesized and served as the auxiliary curing agent, whose accurate molecular structure has been confirmed by different characterizations. The self-healing coating with reversible dynamics network based on hydrogen bonds was prepared by crosslinking through epoxy resin and mixed curing agent of polyetheramine D230 and GD230. Various measurements have been adopted to evaluate the self healing and anticorrosion performance. Results showed that the functional coating with a ratio of 8:2 for D230 to GD230 has satisfied both performances on the steel substrate. After immersion in 3 wt% NaCl solution for 120 days, the impedance value of functional coating still remains about 1010 Ω cm2. After the coating was scratched and immersion for 96 h, the impedance value of functional coating increased by about two orders of magnitude compared to that in blank coating. Mechanical testing and theoretical calculations were used to support dynamic crosslinking model to reveal the self-healing mechanism.

The healing mechanism of traditional self-healing coatings can be divided into “extrinsic” and “intrinsic” types according to the reactants, among which intrinsic restorations can be recycled multiple times and have great potential for applications. But epoxy resin is difficult to achieve intrinsic healing process through secondary bonding and reaction between polymers owing to the high chain rigidity and cross-linking density. In this study, a composite coating combining both “extrinsic” and “intrinsic” healing methods has been fabricated by adding a novel polymer filler (MBT-PGMS), which was synthesized via grafting copolymerization of glycidyl-methacrylate, styrene, methyl-methacrylate and 2-mercaptobenzothiazole (MBT). Multiple analytical techniques have been used to characterize the structure and properties of fillers, and the effect on the anti-corrosion performance and self-healing efficiency of epoxy coatings in 3 wt.% NaCl solution has been studied by electrochemistry measurements and mechanical analysis. Results indicated that the intact coating containing MBT-PGMS (MBT-PGMS/EP) showed prominent corrosion resistance during the immersion of 90 days. Once the coating was scratched, the impedance of MBT-PGMS/EP increased gradually with increasing the immersion time, and reached the optimal performance as the filler amount at 5 wt.%, while the impedance modulus was about 2.8 × 108 Ω cm2 after immersion for 144 h. A dynamic crosslinking model in MBT-PGMS/EP has been proposed to explain the self-healing mechanism.

To improve the crystallinity of poly(bisphenol-A carbonate) (PC). Polyamide-66 (PA-66) is ionized by CaCl _2 to prepare the various degrees of ionization (DIs) of PA-66 ionenes (CaCl _2 –PA-66) as nucleating agents to co-modify PC with cholesterol nonanoate (CN) as plasticizers. Compared with non-ionized PA-66, CaCl _2 –PA-66 enhance the crystallinity of PC. Concretely, with the DI of CaCl _2 –PA-66 is raised from 0 to 37.2 mol%, the crystallinity of PC/CN/CaCl _2 –PA-66 (90/5/5 w/w/w) is first increased from 19.2% to 31.5% and then decreased to 16.9%. This is attributed to the stronger ion-dipole interactions between the ionized nucleating agents and PC, which enhance the compatibility and further dispersibility to create finer crystal with a denser distribution, and the nucleation efficiency is elevated thus facilitating the PC crystallization. However, when the DI of CaCl _2 –PA-66 is overly high (≥11.4 mol%), it leads to excessive ionic crosslinking, which reduces dispersibility and nucleation efficiency. Therefore, the modification of PC with a suitable DI of CaCl _2 –PA-66 can advance its crystallinity, which is a novel and effective approach.