Fabrication of poly(acrylic acid)/boron nitride composite hydrogels with excellent mechanical properties and rapid self-healing through hierarchically physical interactions

Many living tissues possess excellent mechanical properties and self-healing ability. To mimic these living tissues, a series of novel composite hydrogels, poly(acrylic acid)/surface-modified boron nitride nanosheets (PAA/BNNS-NH2) were fabricated simply through hierarchically physical interactions: molecular-scale metal coordination interaction between -COOH of PAA and Fe3+ and nanoscale H-bond between -COOH of PAA and -NH2 of BNNS-NH2. The composite hydrogels exhibit both excellent mechanical properties (including enhanced fracture stress, elongation, toughness, Young's modulus, and dissipated energy) and rapid healing ability without any external stimulus. Especially, the B0.5P70 (the hydrogel with BNNS concentration of 0.5 mg mL- 1, the water content of 70 wt%) exhibits a fracture stress of ~ 1311 kPa and toughness of ~ 4.7 MJ m- 3, almost ~ 3 times and ~ 8 times to B0P70, respectively. The excellent properties, combined with the simple preparation method, endow these composite hydrogels with potential applications.