Self-healing supramolecular waterborne polyurethane dispersions with quadruple hydrogen bonds in main chain

A facile method for preparing supramolecular waterborne polyurethane (WPU) based on quadruple hydrogen bonds (4H-WPU) is reported. Herein, 4H-WPU with quadruple hydrogen bonds in main chain were synthesized by poly (1,4-buthylene-neopentylene adipate glycol) as soft segment, 2-ureido-4[1H]-pyrimidinone (UPy) functionalized monomer, isophorone diisocyanate, 2,2-Bis(hydroxymethyl)propionic acid (hydrophilic monomer), isophorondiamine, triethylamine (neutralizer), and monoethanolamine (blocking agent) as hard segment. The molecular weight of 4H-WPU was controlled around 18,000 consistently. The properties of 4H-WPU with different content of hydrophilic group, hard segment, and UPy units were characterized and the results could provide the reference for preparing supramolecular WPU with high mechanical and self-healing performance while maintaining dispersion stability. The tensile strength of 4H-WPU was 10 times of the blank sample. The healing time of scratched 4H-WPU film was inversely proportional to the content of UPy- functionalized monomer and the shortest healing time is 2.5 hr at 80°C. Mechanical performance of healed films can be restored to more than 90%.