Chemical and oxidation level dependence of mechanical response to uniaxial tensile stress in mono-layered GO nano-flakes

The mechanical behavior of graphene oxide (GO) is governed by both its oxidation level and the nature of its functional groups. Using reactive molecular dynamics simulations, we systematically investigate GO monolayers subjected to uniaxial tension across a wide oxidation range (2%–45%) and varying hydroxyl-to-epoxide ratios and give an insight of the mechanical properties. We compute Young's modulus, tensile strength, and ultimate strain at both 0 K and room temperature. Our results show that while Young's modulus and strength degrade steadily with increasing oxidation, ductility may exhibit a non-monotonic trend, with a peak near 30% oxidation, depending on the functional group composition. Hence, both the oxidation level and the oxidizing groups composition affect the mechanical response in the elastic and plastic deformation regimes: hydroxyl-rich GO displays higher Young's modulus and strength, whereas epoxide-rich GO enhances ductility through bond rearrangements that delay fracture. The role of functional group chemistry can be significant, especially in the plastic regime, at medium/high oxidation levels, evidencing the importance of structural control in tuning GO's mechanical properties. These findings provide a detailed atomistic framework for the design of mechanically optimized GO-based materials.