Self-healing and malleable waterborne polyurethane bearing aliphatic disulfide linkages with hydrophobic branching chains

Self-healing polymers have attracted extensively interests to improving durability of materials. A promising strategy to prepare self-healing materials is the incorporation of dynamic disulfide bonds into polymer backbones. In this study, a novel hydrophobic chain extender containing disulfide bond (CY-OA) has been successfully synthesized and used to elevate the practical application capability of the self-healing WPU. FT-IR and Raman spectra confirmed that the disulfide bonds were successfully incorporated into the polyurethane backbones. The synthetic self-healing waterborne polyurethanes (SHWPUs) all had the high-water contact angle above 108° and the low water absorption below 5%, exhibiting the good hydrophobicity and water resistance. Increasing addition of CY-OA simultaneously optimized the mechanical properties and self-healing efficiency of SHWPUs. The mechanical properties of repaired SHWPU-4 film had been almost recovered to its original values (tensile strength and elongation at break were 12.79 MPa and 1003%) at 120 °C for 1 h. Meanwhile, the feature of dynamic disulfide bonds produced a relatively low activation energy of 54.78 kJ/mol, resulting in a good self-healing efficiency of 93%. Therefore, this hydrophobic self-healing WPU contributed the scratch resistance, water resistance, reprocess ability and further got the feasibility of practical applications.