Yield stress, thixotropy and shear banding in a dilute aqueous suspension of few layer graphene oxide plateletsElectronic supplementary information (ESI) available. See DOI: 10.1039/c3sm50708d

We demonstrate a rigidity percolation transition and the onset of yield stress in a dilute aqueous dispersion of graphene oxide platelets (aspect ratio 5000) above a critical volume fraction of 3.75 10 4 with a percolation exponent of 2.4 0.1. The viscoelastic moduli of the gel at rest measured as a function of time indicate the absence of structural evolution of the 3D percolated network of disks. However a shear-induced aging giving rise to a compact jammed state and shear rejuvenation indicating a homogenous flow is observed when a steady shear stress ( ) is imposed in creep experiments. We construct a shear diagram ( vs. volume fraction ) and the critical stress above which shear rejuvenation occurs is identified as the yield stress y of the gel. The minimum steady state shear rate &z.ggrda; m obtained from creep experiments agrees well with the end of the plateau region in a controlled shear rate flow curve, indicating a shear localization below &z.ggrda; m . A steady state shear banding in the plateau region of the flow curve observed in particle velocimetry measurements in a Couette geometry confirms that the dilute suspensions of GO platelets form a thixotropic yield stress fluid. We demonstrate that percolated network of non-aggregating GO platelets (aspect ratio 5000) form a thixotropic yield stress fluid above the volume fraction ( c ) > 3.75 10 4 .