The dispersion of carbon nanoparticles (CNP) is important role in many applications. To stabilize CNP in solvents, polymer can be utilized to avoid the aggregation of CNPs with steric effects. In experiments, it has been found that PVP (Poly vinyl pyrrolidone) is a good stabilizer for Carbon nanotubes. This polymer is commercial, inexpensive, water-soluble, and has many other practical applications (pharmaceuticals, cosmetics, coatings, etc.) In our work, the stability of PVP grafted CNP (P-CNP) is investigated with Dissipative Particle Dynamics (DPD) simulation techniques. The conformation of P-CNP is obtained in water solution after the system of CNP and PVP in water reaches equilibrium. Then, the P-CNP is released into a Couette flow channel and a Poiseuille flow channel. CNPs with different shapes (cylinder, sphere and thin sheet) are investigated, corresponding to carbon nanotubes and graphene sheets. Simulation results indicated that PVP could detach from the CNP because the physical interaction between PVP and CNP was overcome under high shear stress. The critical shear rate (the rate at which PVP begins separating from the CNP) was determined at different particle shapes. Depending on shear rate, P-CNP could be in one of three conditions: (a) stably dispersed, (b) affected by the flow, i.e., a transition state, and (c) in a fully separated state in water flow. The shape of the P-CNP plays a role in the development of each of these states, and this is what will be discussed in this presentation.
The financial support of the Advanced Energy Consortium (AEC BEG08-022) and the computational support of XSEDE (CTS090017) are acknowledged.