The effects of hydroxide and epoxide functional groups on the mechanical properties of graphene oxide and its failure mechanism by molecular dynamics simulations.

Graphene oxide (GO) could be assembled via amphiphilic interface adhesion into nano-composites. The deformation behaviors and mechanical properties of the composites are sensitive to the functional species absorbed on GO, which are investigated by molecular dynamics simulations. It is found that the ultimate stress and elastic modulus decreases greatly as the density of function groups absorbed on GO increase from 10% to 50%, but independent on the group type of hydroxide or epoxide ones. Fracture of GO is always initiated and preferentially propagated along the path on which hydroxide or epoxide groups are distributed. Essentially, hydroxide or epoxide groups will weaken the adjacent C-C bonds and induce structure transformation from honeycomb to diamond-like structure as result of hybridization transition from sp2 to sp3. The findings provide us a guidance for the design of GO based composites.