Exceptional Mechanical Properties of Phase-Separation-Free MoSe-Chain-Reinforced Hydrogel Prepared by Polymer Wrapping Process.

As MoSe 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 MoSe-chain-nanowire-gelatin composite hydrogel is prepared simply by mixing MoSe nanowires with gelatin, phase separation of the MoSe nanowires from the gelatin matrix occurs in the micronetwork, providing only small improvements in their mechanical properties. In contrast, when the surface of the MoSe nanowire is wrapped with the gelatin polymer, the chemical compatibility of the MoSe nanowire with the gelatin matrix is significantly improved, which enables the fabrication of a phase-separation-free MoSe-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 MoSe 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.