Mussel-inspired waterborne PU recovers 98% of strength after damage

A dual dynamic network enabled the polyurethane film to combine high strength and extensibility with thermally activated self-healing.

The material combines dopamine-derived catechol groups, aromatic disulfide bonds and reversible coordination with iron ions. The researchers designed this dual dynamic network to address the usual trade-off between mechanical strength and healing efficiency in self-healing polymers.

The approach was inspired by the byssal threads that marine mussels use to attach themselves to wet surfaces. Catechol chemistry and reversible metal coordination contribute to the strength, toughness and damage tolerance of the natural material.

Ke Pan, Jinlin Li, Li Liu and Guangfeng Wu of Changchun University of Technology incorporated dopamine-derived catechol groups and aromatic disulfide bonds into a waterborne polyurethane using step-growth polymerisation.

Ferric chloride was then added to provide Fe³⁺ ions. These ions formed reversible coordination interactions with catechol groups and potentially with carboxylate groups derived from dimethylolpropionic acid in the polyurethane network.

The coordination bonds and dynamic disulfide bonds can break and reform as the material is deformed or heated. This allows the network to dissipate energy under load while also rearranging across a damaged interface during healing.

At the optimum ferric chloride concentration of 0.1 wt%, the polyurethane film achieved a tensile strength of 29.8 MPa and an elongation at break of 553.2%. Its measured toughness was 83.3 MJ/m³.

After the damaged material was held at 60°C for two hours, it recovered 98.2% of its original tensile strength.

The researchers said the results demonstrate that combining several reversible interactions can provide a better balance between mechanical performance and healing capability than relying on a single dynamic mechanism.

The healing process nevertheless requires both heat and time, and the reported results were obtained from experimental films rather than a commercial coating or finished product. Further work would be needed to establish repeated healing performance, environmental durability and suitability for industrial processing.

The study, “Mussel-Inspired Self-Healing Waterborne Polyurethanes With Catechol–Fe³⁺ Coordination and Dynamic Disulfide Bonds”, was published online in the Journal of Polymer Science on 28 September 2026.