A molecular dynamics approach to examine the kinetics of the capillary imbibition of a polymer at nanoscale

A molecular dynamics (MD) approach was employed to simulate the imbibition of a designed nanopore by a polymer. The length of imbibition as a function of time for various interactions between the polymer and the pore wall was recorded for this system (i.e., polymer and nanopore). By and large, the kinetics of imbibition was successfully described by the Lucas–Washburn (LW) equation, although deviation from it was observed in some cases. This nonuniformity contributes to the neglect of the dynamic contact angle (DCA) in the LW equation. Two commonly used models (i.e., hydrodynamic and molecular–kinetic models) were thus employed to calculate the DCA. It is demonstrated that none of the evaluated models is able to justify the simulation results in which are not in good agreement with the simple LW equation. Further investigation of the MD simulation data revealed an interesting fact that there is a direct relationship between the wall–polymer interaction and the speed of the capillary imbibition. More evidence to support this claim will be presented.