Introducing imide-based functional groups for enhanced self-healing properties of polyurethane*

A functional polyurethane with imide moiety (PUI) is synthesized and the self-healing properties are compared with conventional polyurethane (PU). As the imide-based molecules with either mono-hydroxyl or di-hydroxyl groups are added to the mixtures of reactants including polyols and cross-linkers, the imide groups are successfully incorporated to the polyurethane chains. Therefore, while the mono-hydroxyl imide-based molecules give only interacting sites to PU chains, the di-hydroxyl imide-based molecules provide both interacting sites and chemical crosslinks. Interestingly, despite a small amount of the imide moiety in polyurethane, it is observed that the self-healing properties are drastically enhanced as compared to those of PU. Especially, PUI based on imide derivative with di-hydroxyl groups exhibits more excellent self-healing performances compared with that with mono-hydroxyl groups because of the unique intermolecular networks of reversible interactions and chemical crosslinks.