Multiple hydrogen bonding in crosslinked graphene oxide films with improved stretchability and toughness†

Abstract

Transforming the microscopic graphene oxide (GO) nanosheets into macroscopic film materials holds significant promise for various applications. However, those GO films normally suffer from low tensile strength and poor toughness. Optimizing the assembly of GO nanosheets, especially in designing the interactions between adjacent nanosheets, remains challenging. Herein, inspired by mussels, we incorporated polymer rich in UPy functional units into GO films, namely GUPy films. The multiple hydrogen bonding between the UPy units and oxygen-containing groups on GO nanosheets resulted in highly stretchable and tough GO films. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of UPy in the films, revealing tightly linked layered structures at the microscopic level. Macroscopically, the films displayed exceptional flexibility, withstanding folding and curling without damage. Tensile tests demonstrated the superior mechanical properties of the GUPy film, which boasts a Young's modulus of 1100.5 MPa, fracture strain of 24.0%, tensile strength of 183.5 MPa, and toughness of 19.5 MJ m⁻³. These values are 2.3, 2.4, 6.0, and 12.2 times higher than those of pure GO films, respectively, and significantly exceed those of control films lacking UPy. Additionally, cyclic tensile tests confirmed the excellent energy dissipation capability of the GUPy film. This bio-inspired strategy offers a promising route for developing high-performance two-dimensional materials, expanding their potential applications.