Orientation dynamics of dilute functionalized graphene suspensions in oscillatory flow

Abstract

The dynamics of molecularly thin graphene sheets in transient flows are important to understand their behavior in suspension and during processing. Scattering dichroism is used to evaluate changes in the orientation distribution function in dilute suspensions. To evaluate if the graphene sheets behave as flexible sheets or as more rigid flat particles, the results are compared with numerical computations of the single-particle Smoluchowski equation for flat spheroidal particles. In particular, the evolution of the orientation angle in oscillatory flows as a function of increasing amplitude is studied. The results show that even when taking an average rotational diffusivity, the results for the polydisperse graphene sheets show all the hallmarks of the motion of rigid disks, including a frequency doubling of the time-dependent orientation signal. The results indicate that the motion of functionalized graphene sheets in suspension is consistent with flat rigid objects.