Brownian dynamics simulation of two-dimensional nanosheets under flow

Conformations and alignments of the nanosheets need to be controlled in order to achieve the properties of these materials. One common way to manufacture nanosheet-based materials is liquid processing. As liquid processing can greatly affect the conformations and alignments of the nanosheets, a detailed study of the flow-induced morphology dynamics of nanosheets is much needed. However, current research on dispersed nanosheets in liquid phase is either under equilibrium state or over a timescale that is undetectable in experiments. To fulfill this need, we aim to develop a coarse-grained Brownian dynamics simulation algorithm to study the morphology change of dispersed nanosheets under flow fields over a timescale that is accessible in experimental procedures. We use a coarse-grained bead-rod lattice model to represent the nanosheets and analyze the force fields on the beads (constraint, metric, bending, drag and Brownian). We solve for the trajectory of the beads using a midstep explicit timestepper and calculate the morphology properties and intrinsic viscosity. Simulations are performed under shear flow and biaxial extensional flow respectively and we vary the sheet size, shear/extensional rate, and bending moduli to study their impact on the conformation and alignments of nanosheets and also the intrinsic viscosity of the solution. The results indicate that our model can successfully study the morphology change of dilute nanosheets under different flow field and can serve as a basic framework for the study of nanosheet morphology under liquid processing procedures such as spin coating, dip coating, doctor blade coating and roll coating.