Stiff UV-Curable self-healing coating based on double reversible networks containing diels-alder cross-linking and hydrogen bonds

[Display omitted] •Multi-arm UV-cured polyurethane (PU) pre-polymers were prepared.•A series of self-healing coatings containing Diels-Alder cross-linking and hydrogen bonds were developed.•The self-healing coatings showed high repair efficiency and high hardness. A series of multi-crosslinkable, self-healing coatings were developed to enhance the mechanical properties through tandem UV-curing and Diels-Alder (DA) chemistry. First, multi-arm UV-cured polyurethane (PU) pre-polymers (IPxH12) were prepared based on cyclotriphosphazene monomer (H12) with more benzene ring structure and half-blocked photosensitive oligomer. Then N, N'-(4, 4′-methylenediphenyl) bismaleimide (BMI) and furfuryl alcohol (FA) were used as the raw materials to prepare DA intermediate by Diels-Alder reaction. The DA intermediate was further reacted with methacrylic acid isocyanate (IEM) to obtain the modified IDA monomer (UV curable DA monomer, containing acrylic double bond). The structure of IPxH12 and IDA was characterized by FT-IR and 1H-NMR. UV-cured self-healing coatings were prepared by designing some coating formulations with the IPxH12, IDA and initiator. The self-healing properties and mechanical properties of the coatings were investigated. The results revealed that the hardness of the coating was up to 3H, and the introduction of IDA improved its self-healing performance, when the ratio of DA monomer to PU was 2:1, the repair effect was the best. The UV-curable self-healing coating has potential application in metal protection and other fields.