Connecting the viscoelastic response of nanosheet gels to the elastic properties of the particles*

Micron-sized nanosheets such as graphene, graphene oxide or clay platelets can be used to make conducting inks or as fillers in composites to enhance their mechanical properties. At high concentrations beyond rigidity percolation, nanosheet suspensions become yield stress fluids with a finite storage modulus. In this regime the elastic response of nano-sheet suspensions appears to be universal. The storage modulus plateau of few-layer graphene in NMP solvent, aqueous graphene oxide gels and clays exhibit a power law exponent close to 3 as a function of relative volume fraction.
We present a new analytical model that explains this behaviour and connects the bulk response to the elastic properties of single nanosheets and their size. This allows is to infer the magnitude of the bending stiffness of single nano-sheets from our rheological data.
This model opens up the possibility to infer elastic properties of different nanosheets from rheological data of the suspension rather than performing AFM experiments on single nano-sheets. Furthermore, this model may explain the mechanical enhancement of nanosheet composites where a similar exponent can be observed.