Fully Physically Cross-Linked Double Network Hydrogels with Strong Mechanical Properties, Good Recovery and Self-healing Properties
Combining a hydrophobic interactions crosslinked Curdlan as the first network and hydrophobic interactions crosslinked polyacrylamide as the second network, we have fabricated a Curdlan/HPAAm Double network (DN) hydrogel using a one-pot method. The resulting DN hydrogel exhibited good mechanical properties, i.e. elastic modulus of 102.65 kPa, tensile fracture strength of 0.81 MPa, tensile stretch of 25.33 and compressive stress of 62.50 MPa when the compressive strain increased up to 99%. The DN gel could withstand ten times compression tests under 90% compressive strain without observable damage. The DN gel demonstrated 84% stiffness recovery and 97% toughness recovery after the deformed samples were relaxed and stored at 95 oC for 4 h. The stiffness and fracture stress of the DN gel were enhanced after sterilization treatment at 120 oC. Furthermore, the gels demonstrated 52% self-healing of fracture stress after the samples were cut and brought into contact at 95 oC for 4 h. The self-recovery and self-healing properties of DN gel both originated from the first Curdlan network via the reformation of hydrophobic interaction and the second HPAAm network via reformation of the broken hydrophobic associations.