A Self-Healing Transparent Waterborne Polyurethane Film with High Strength and Toughness Based on Cation−π Interactions

Giving waterborne polyurethane (WPU) coatings self-healing properties not only maintains the coating's environmentally friendly characteristics but also extends the material's service life and enables sustainable development. Therefore, self-healing WPUs have received an increasing amount of attention from researchers. However, it is a serious challenge to overcome the original shortcomings of WPU coatings, such as poor strength, low hardness, and weak adhesion, as well as the introduction of self-healing properties resulting in further degradation of strength-mechanical properties and heat resistance. Here, we provide a design strategy to introduce a noncovalent physical cross-linking network based on cation-π interactions into the WPU molecular structure to prepare a series of self-healing transparent WPU coatings with high strength. The coating exhibited a very high tensile strength (66.11 ± 3.28 MPa) and excellent flexibility (0.5 mm), with a scratch repair efficiency of up to 98.2% for 12 h of repair at 60 °C. In addition, the coating also has good optical properties and has broad application prospects in the fields of transparent protective coatings and adhesives.