A mechanically robust double-network hydrogel with high thermal responses via doping hydroxylated boron nitride nanosheets

Double-network (DN) hydrogel which possesses many superior performances such as excellent toughness, viscoelasticity and self-healing ability has become promising biomaterials. However, lack of thermal conductivity and moderate adhesiveness has greatly limited their application as load-bearing cartilage substitutes. Boron nitride itself has good rigidity and thermal conductivity but poor water solubility. Hydroxylated boron nitride nanosheets (OH-BNNSs) which have been previously reported have good water solubility (~ 0.6 mg/mL) and to obtain a homogeneous and stable dispersion. In this work, we introduced OH-BNNS into DN hydrogel to obtain high thermal conductivity and toughness hydrogel. The DN hydrogel is a class of physically double-network hydrogel with hydrophobic association polyacrylamide (PAM) and partly crystalline polyvinyl alcohol (PVA). Impressively, the obtained PVA/PAM/BNNS composite hydrogel possesses super-flexibility, high toughness, good thermal conductivity, appropriate tissue adhesiveness and stimuli-free self-healing ability. Therefore, the composite hydrogel overcomes the poor mechanical strength and locally overheating issues as cartilage substitutes and may also become alternatives for antipyretic pastes.