Preparation of living and highly stable blended polyurethane emulsions for self-healing films with enhancive toughness and recyclability

Widely applied waterborne polyurethane (WPUs) are expected to be functionalized with excellent mechanical property, ideal self-healing performance and desired recyclability, but it is a great challenge to integrate these attractive properties into a one-pot WPU platform. Herein, a novel double ingredients waterborne polyurethane (2K-WPU-DA-x), found on the furan modified WPU-F and maleimide decorated WPU-M dispersions for DielsAlder (DA) cross-linking reactions, was designed and projected which exhibited interesting enhancedmechanical, self-healable and recyclable properties. The stability and appearance of these novel waterborne polyurethane emulsions were well studied. In the following, the reversible nature of direct DA/retroDA reactions within the 2K-WPU-DA-x was extensively analyzed via FT-IR, UV-vis, and DSC measurements. On account of the DA bonds resulted a cross-linked structure of 2K-WPU-DA-1/1, the stress and strain at the break increased by more than 20 MPa and 250% respectively compared with linear structural WPU-F. At the same time, relying on the thermal-responsive dissociation/reassociation of DA covalent bonds, 2K-WPU-DA-x films shown outstanding self-healing ability, with a self-healing efficiency beyond 95%. Moreover, owing to the reversibility of 2K-WPU-DA-x, the networks exhibited readily recyclable and reshaping properties, showing a desired thermoplasticity.