Polyrotaxane-modified waterborne polyurethane based on H-bonding and metal bonding with mechanically tough and self-healability

The pulley structure has been widely employed to improve mechanical properties. Polyrotaxane-based waterborne polyurethane (WPU) typically exhibits good tensile strength and Young's modulus. However, achieving outstanding self-healability of polyrotaxane-based WPU under mild conditions generally proves insufficient solely relying on host-guest interactions. Herein, a strategy that constructs a triple synergy of host-guest interaction, hydrogen bonds, and metal coordination bonds by sequentially introducing tannic acid (TA) and Fe 3+ is proposed to prepare polyrotaxane-based WPU with excellent mechanical performance and high self-healable capability. Besides the reversible non-covalent bonding contributing to intrinsic self-healing, the unique sliding motion of WPU's molecule chain acts as a driving force, promoting efficient contact among reversible bonds. Notably, benefiting from the sliding motion of β-cyclodextrin (β-CD) along a chain, the dynamic reconstruction of hydrogen bonds and metal coordination bonds, the resulting supramolecular WPU exhibited a tensile strength of 46.05 MPa and a toughness of 130.30 MPa, with satisfactory self-healing performance (tensile strength healing efficiency of more than 95%). This work enriches the self-healing mechanism and expands the concepts for the design of resilient self-healing environmentally friendly supramolecular WPU.