Reversible Covalent Bond Assisted Plastic-stretching: a strategy towards Graphene Oxide Films with Superior Modulus

Efforts to obtain Graphene Oxide (GO) films with high mechanical properties have been frustrated by the misalignment of GO sheets and wrinkles in the films. While plastic-stretching GO films can improve the alignment of GO sheets and flatten the wrinkles, the misalignment and wrinkles regenerate after stretch release because of the weak and unstable interaction between GO sheets. In this work, high-strength covalent bonds (C-O-B) are introduced between GO sheets to maintain the stretch-induced orientation of GO sheets. After optimization, the fracture strength and Young’s modulus were respectively improved by 24.3% and 110.3% to 167.3 MPa and 108.1 GPa. Moreover, the as-prepared films exhibit only a marginal property degradation in harsh environments (85°C, 85% relative humidity, 96h) when applied a thin Polyurethane coating on the surface to prevent the hydrolysis of C-O-B covalent bond, which demonstrates the potential for practical applications. This new strategy is expected to extend the processing capability and enhance the mechanical properties of other laminated materials such as graphene, black phosphorus, MXene, and so on.