Variations\nof Rheological Properties and Wall Slip\nof Polyethylene in Nanoconfined Channels Studied by MD Simulation

In this work, the all-atom molecular dynamics (MD) simulation\nis\nemployed to study the flow characteristics of polyethylene (PE) melts\nin a nanoconfined system. Except for the wall slip, the deviations\nof the non-Newtonian index of PE melts in the nanochannel from the\nbulk fluid were found. The simulation results demonstrated that the\nslip velocity (<i>v</i><sub><i>s</i></sub>) follows\nthe power law <i>v</i><sub><i>s</i></sub> = <i>a</i>τ<i><sup>b</sup><sub>w</sub></i>, and its\ncorrelation with the wall–fluid interaction was analyzed. More\nimportantly, the anisotropic conformation of PE molecules and its\ndiscrepancy with the nonconfined system was manifested by the radius\nof gyration. The non-Newtonian index increased closer to 1 as the\nslit height decreased due to the elongation of polymer chains in the\nflow direction. The migration of polymer chains became smoother, and\ntwo fluid layers near the wall almost not exchanging with bulk region\nmolecules were found. This work provides helpful insights for understanding\nnanoscale non-Newtonian fluid hydrodynamics behaviors.