Self-healable poly(acrylic acid-: co -maleic acid)/glycerol/boron nitride nanosheet composite hydrogels at low temperature with enhanced mechanical properties and water retention

© 2019 The Royal Society of Chemistry. Many living tissues possess excellent mechanical properties and water retention which enable them to self-heal at room temperature even below the freezing temperature of water. To mimic the unique features of living tissue, a poly(acrylic acid-co-maleic acid) composite hydrogel with enhanced mechanical properties and remarkable water retention was fabricated under accessible conditions. The hydrogel is functionalized by amino group modified boron nitride nanosheets (BNNS-NH 2 )/glycerol and exhibits self-healing abilities at low temperature. The self-healing process occurs through the re-establishing of hydrogen bonds and metal coordination interactions at the damaged surfaces. Its anti-freezing abilities enable the hydrogel to self-heal at -15 °C, and the self-healing efficiency based on tensile strength reaches up to ∼70%. Moreover, glycerol also endows the hydrogel with long-lasting water retention, which remains a water content of ∼99 wt% for more than 30 days. Meanwhile, the simultaneous introduction of BNNS-NH 2 and glycerol significantly improved the mechanical properties of the hydrogel, which displays great stretchability (∼474%), tensile strength (∼151.3 kPa), stiffness (Young's modulus of ∼62.75 kPa) and toughness (∼355.13 kJ m -3 ). It is anticipated that these novel hydrogels will develop many fields and be exploited for new applications in extensive external environments.