Exceptional Mechanical Properties of Phase-Separation-Free Mo 3 Se 3 - -Chain-Reinforced Hydrogel Prepared by Polymer Wrapping Process

As Mo Se chain nanowires have dimensions comparable to those of natural hydrogel chains (molecular-level diameters of ∼0.6 nm and lengths of several micrometers) and excellent mechanical strength and flexibility, they have large potential to reinforce hydrogels and improve their mechanical properties. When a Mo Se -chain-nanowire-gelatin composite hydrogel is prepared simply by mixing Mo Se nanowires with gelatin, phase separation of the Mo Se nanowires from the gelatin matrix occurs in the micronetwork, providing only small improvements in their mechanical properties. In contrast, when the surface of the Mo Se nanowire is wrapped with the gelatin polymer, the chemical compatibility of the Mo Se nanowire with the gelatin matrix is significantly improved, which enables the fabrication of a phase-separation-free Mo Se -reinforced gelatin hydrogel. The composite gelatin hydrogel exhibits significantly improved mechanical properties, including a tensile strength of 27.6 kPa, fracture toughness of 26.9 kJ/m , and elastic modulus of 54.8 kPa, which are 367%, 868%, and 378% higher than those of the pure gelatin hydrogel, respectively. Furthermore, the amount of Mo Se nanowires added in the composite hydrogel is as low as 0.01 wt %. The improvements in the mechanical properties are significantly larger than those for other reported composite hydrogels reinforced with one-dimensional materials.