Study on waterborne self-healing polyurethane with dual dynamic units of quadruple hydrogen bonding and disulfide bonds

The novel self-healable waterborne polyurethanes (WPU) with the synergistic reversible units of aliphatic disulfide bonds and quadruple hydrogen bonding have been successfully prepared. The ureidopyrimidone (UPy) functional motifs were introduced into polymer backbones of polyurethane, where also placed the reversible disulfide bonds. The quadruple hydrogen bonds of UPy groups endowed the material a strong physical cross-linking network, which provided a superior Young's moduli. The features of dual dynamic structure could also produce a relatively low active energy of 36.1 kJ/mol, resulting in a good self-repairing efficiency of 94% under a mild condition. Furthermore, the influence of self-healing time and different repairing temperature on the healed performance was also systematically investigated. In order to describe the self-healing progress of multiple dynamic units, a physical model was used to study the evolution of self-repairing efficiency with variable healing time, indicating that quadruple H-bonding and disulfide bonds predominantly supported time dependent reconstruction of physically crosslinking network to recover the original mechanical property.